Revert "bpo-28533: Remove asyncore, asynchat, smtpd modules (GH-29521)" (GH-29951)

This reverts commit 9bf2cbc4c498812e14f20d86acb61c53928a5a57.

28 files changed, 3228 insertions, 34 deletions

diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
index 82f81e3..ce5121e 100644
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -130,6 +130,8 @@ Lib/ast.py                    @isidentical
 
 **/*typing*                   @gvanrossum @Fidget-Spinner
 
+**/*asyncore                  @giampaolo
+**/*asynchat                  @giampaolo
 **/*ftplib                    @giampaolo
 **/*shutil                    @giampaolo
 
diff --git a/Doc/library/asynchat.rst b/Doc/library/asynchat.rst
new file mode 100644
index 0000000..9e51416
--- /dev/null
+++ b/Doc/library/asynchat.rst
@@ -0,0 +1,213 @@
+:mod:`asynchat` --- Asynchronous socket command/response handler
+================================================================
+
+.. module:: asynchat
+   :synopsis: Support for asynchronous command/response protocols.
+
+.. moduleauthor:: Sam Rushing <rushing@nightmare.com>
+.. sectionauthor:: Steve Holden <sholden@holdenweb.com>
+
+**Source code:** :source:`Lib/asynchat.py`
+
+.. deprecated:: 3.6
+   Please use :mod:`asyncio` instead.
+
+--------------
+
+.. note::
+
+   This module exists for backwards compatibility only.  For new code we
+   recommend using :mod:`asyncio`.
+
+This module builds on the :mod:`asyncore` infrastructure, simplifying
+asynchronous clients and servers and making it easier to handle protocols
+whose elements are terminated by arbitrary strings, or are of variable length.
+:mod:`asynchat` defines the abstract class :class:`async_chat` that you
+subclass, providing implementations of the :meth:`collect_incoming_data` and
+:meth:`found_terminator` methods. It uses the same asynchronous loop as
+:mod:`asyncore`, and the two types of channel, :class:`asyncore.dispatcher`
+and :class:`asynchat.async_chat`, can freely be mixed in the channel map.
+Typically an :class:`asyncore.dispatcher` server channel generates new
+:class:`asynchat.async_chat` channel objects as it receives incoming
+connection requests.
+
+
+.. class:: async_chat()
+
+   This class is an abstract subclass of :class:`asyncore.dispatcher`. To make
+   practical use of the code you must subclass :class:`async_chat`, providing
+   meaningful :meth:`collect_incoming_data` and :meth:`found_terminator`
+   methods.
+   The :class:`asyncore.dispatcher` methods can be used, although not all make
+   sense in a message/response context.
+
+   Like :class:`asyncore.dispatcher`, :class:`async_chat` defines a set of
+   events that are generated by an analysis of socket conditions after a
+   :c:func:`select` call. Once the polling loop has been started the
+   :class:`async_chat` object's methods are called by the event-processing
+   framework with no action on the part of the programmer.
+
+   Two class attributes can be modified, to improve performance, or possibly
+   even to conserve memory.
+
+
+   .. data:: ac_in_buffer_size
+
+      The asynchronous input buffer size (default ``4096``).
+
+
+   .. data:: ac_out_buffer_size
+
+      The asynchronous output buffer size (default ``4096``).
+
+   Unlike :class:`asyncore.dispatcher`, :class:`async_chat` allows you to
+   define a :abbr:`FIFO (first-in, first-out)` queue of *producers*. A producer need
+   have only one method, :meth:`more`, which should return data to be
+   transmitted on the channel.
+   The producer indicates exhaustion (*i.e.* that it contains no more data) by
+   having its :meth:`more` method return the empty bytes object. At this point
+   the :class:`async_chat` object removes the producer from the queue and starts
+   using the next producer, if any. When the producer queue is empty the
+   :meth:`handle_write` method does nothing. You use the channel object's
+   :meth:`set_terminator` method to describe how to recognize the end of, or
+   an important breakpoint in, an incoming transmission from the remote
+   endpoint.
+
+   To build a functioning :class:`async_chat` subclass your  input methods
+   :meth:`collect_incoming_data` and :meth:`found_terminator` must handle the
+   data that the channel receives asynchronously. The methods are described
+   below.
+
+
+.. method:: async_chat.close_when_done()
+
+   Pushes a ``None`` on to the producer queue. When this producer is popped off
+   the queue it causes the channel to be closed.
+
+
+.. method:: async_chat.collect_incoming_data(data)
+
+   Called with *data* holding an arbitrary amount of received data.  The
+   default method, which must be overridden, raises a
+   :exc:`NotImplementedError` exception.
+
+
+.. method:: async_chat.discard_buffers()
+
+   In emergencies this method will discard any data held in the input and/or
+   output buffers and the producer queue.
+
+
+.. method:: async_chat.found_terminator()
+
+   Called when the incoming data stream  matches the termination condition set
+   by :meth:`set_terminator`. The default method, which must be overridden,
+   raises a :exc:`NotImplementedError` exception. The buffered input data
+   should be available via an instance attribute.
+
+
+.. method:: async_chat.get_terminator()
+
+   Returns the current terminator for the channel.
+
+
+.. method:: async_chat.push(data)
+
+   Pushes data on to the channel's queue to ensure its transmission.
+   This is all you need to do to have the channel write the data out to the
+   network, although it is possible to use your own producers in more complex
+   schemes to implement encryption and chunking, for example.
+
+
+.. method:: async_chat.push_with_producer(producer)
+
+   Takes a producer object and adds it to the producer queue associated with
+   the channel.  When all currently-pushed producers have been exhausted the
+   channel will consume this producer's data by calling its :meth:`more`
+   method and send the data to the remote endpoint.
+
+
+.. method:: async_chat.set_terminator(term)
+
+   Sets the terminating condition to be recognized on the channel.  ``term``
+   may be any of three types of value, corresponding to three different ways
+   to handle incoming protocol data.
+
+   +-----------+---------------------------------------------+
+   | term      | Description                                 |
+   +===========+=============================================+
+   | *string*  | Will call :meth:`found_terminator` when the |
+   |           | string is found in the input stream         |
+   +-----------+---------------------------------------------+
+   | *integer* | Will call :meth:`found_terminator` when the |
+   |           | indicated number of characters have been    |
+   |           | received                                    |
+   +-----------+---------------------------------------------+
+   | ``None``  | The channel continues to collect data       |
+   |           | forever                                     |
+   +-----------+---------------------------------------------+
+
+   Note that any data following the terminator will be available for reading
+   by the channel after :meth:`found_terminator` is called.
+
+
+.. _asynchat-example:
+
+asynchat Example
+----------------
+
+The following partial example shows how HTTP requests can be read with
+:class:`async_chat`.  A web server might create an
+:class:`http_request_handler` object for each incoming client connection.
+Notice that initially the channel terminator is set to match the blank line at
+the end of the HTTP headers, and a flag indicates that the headers are being
+read.
+
+Once the headers have been read, if the request is of type POST (indicating
+that further data are present in the input stream) then the
+``Content-Length:`` header is used to set a numeric terminator to read the
+right amount of data from the channel.
+
+The :meth:`handle_request` method is called once all relevant input has been
+marshalled, after setting the channel terminator to ``None`` to ensure that
+any extraneous data sent by the web client are ignored. ::
+
+
+   import asynchat
+
+   class http_request_handler(asynchat.async_chat):
+
+       def __init__(self, sock, addr, sessions, log):
+           asynchat.async_chat.__init__(self, sock=sock)
+           self.addr = addr
+           self.sessions = sessions
+           self.ibuffer = []
+           self.obuffer = b""
+           self.set_terminator(b"\r\n\r\n")
+           self.reading_headers = True
+           self.handling = False
+           self.cgi_data = None
+           self.log = log
+
+       def collect_incoming_data(self, data):
+           """Buffer the data"""
+           self.ibuffer.append(data)
+
+       def found_terminator(self):
+           if self.reading_headers:
+               self.reading_headers = False
+               self.parse_headers(b"".join(self.ibuffer))
+               self.ibuffer = []
+               if self.op.upper() == b"POST":
+                   clen = self.headers.getheader("content-length")
+                   self.set_terminator(int(clen))
+               else:
+                   self.handling = True
+                   self.set_terminator(None)
+                   self.handle_request()
+           elif not self.handling:
+               self.set_terminator(None)  # browsers sometimes over-send
+               self.cgi_data = parse(self.headers, b"".join(self.ibuffer))
+               self.handling = True
+               self.ibuffer = []
+               self.handle_request()
diff --git a/Doc/library/asyncore.rst b/Doc/library/asyncore.rst
new file mode 100644
index 0000000..a86518e
--- /dev/null
+++ b/Doc/library/asyncore.rst
@@ -0,0 +1,360 @@
+:mod:`asyncore` --- Asynchronous socket handler
+===============================================
+
+.. module:: asyncore
+   :synopsis: A base class for developing asynchronous socket handling
+              services.
+
+.. moduleauthor:: Sam Rushing <rushing@nightmare.com>
+.. sectionauthor:: Christopher Petrilli <petrilli@amber.org>
+.. sectionauthor:: Steve Holden <sholden@holdenweb.com>
+.. heavily adapted from original documentation by Sam Rushing
+
+**Source code:** :source:`Lib/asyncore.py`
+
+.. deprecated:: 3.6
+   Please use :mod:`asyncio` instead.
+
+--------------
+
+.. note::
+
+   This module exists for backwards compatibility only.  For new code we
+   recommend using :mod:`asyncio`.
+
+This module provides the basic infrastructure for writing asynchronous  socket
+service clients and servers.
+
+There are only two ways to have a program on a single processor do  "more than
+one thing at a time." Multi-threaded programming is the  simplest and most
+popular way to do it, but there is another very different technique, that lets
+you have nearly all the advantages of  multi-threading, without actually using
+multiple threads.  It's really  only practical if your program is largely I/O
+bound.  If your program is processor bound, then pre-emptive scheduled threads
+are probably what you really need.  Network servers are rarely processor
+bound, however.
+
+If your operating system supports the :c:func:`select` system call in its I/O
+library (and nearly all do), then you can use it to juggle multiple
+communication channels at once; doing other work while your I/O is taking
+place in the "background."  Although this strategy can seem strange and
+complex, especially at first, it is in many ways easier to understand and
+control than multi-threaded programming.  The :mod:`asyncore` module solves
+many of the difficult problems for you, making the task of building
+sophisticated high-performance network servers and clients a snap.  For
+"conversational" applications and protocols the companion :mod:`asynchat`
+module is invaluable.
+
+The basic idea behind both modules is to create one or more network
+*channels*, instances of class :class:`asyncore.dispatcher` and
+:class:`asynchat.async_chat`.  Creating the channels adds them to a global
+map, used by the :func:`loop` function if you do not provide it with your own
+*map*.
+
+Once the initial channel(s) is(are) created, calling the :func:`loop` function
+activates channel service, which continues until the last channel (including
+any that have been added to the map during asynchronous service) is closed.
+
+
+.. function:: loop([timeout[, use_poll[, map[,count]]]])
+
+   Enter a polling loop that terminates after count passes or all open
+   channels have been closed.  All arguments are optional.  The *count*
+   parameter defaults to ``None``, resulting in the loop terminating only when all
+   channels have been closed.  The *timeout* argument sets the timeout
+   parameter for the appropriate :func:`~select.select` or :func:`~select.poll`
+   call, measured in seconds; the default is 30 seconds.  The *use_poll*
+   parameter, if true, indicates that :func:`~select.poll` should be used in
+   preference to :func:`~select.select` (the default is ``False``).
+
+   The *map* parameter is a dictionary whose items are the channels to watch.
+   As channels are closed they are deleted from their map.  If *map* is
+   omitted, a global map is used. Channels (instances of
+   :class:`asyncore.dispatcher`, :class:`asynchat.async_chat` and subclasses
+   thereof) can freely be mixed in the map.
+
+
+.. class:: dispatcher()
+
+   The :class:`dispatcher` class is a thin wrapper around a low-level socket
+   object. To make it more useful, it has a few methods for event-handling
+   which are called from the asynchronous loop.   Otherwise, it can be treated
+   as a normal non-blocking socket object.
+
+   The firing of low-level events at certain times or in certain connection
+   states tells the asynchronous loop that certain higher-level events have
+   taken place.  For example, if we have asked for a socket to connect to
+   another host, we know that the connection has been made when the socket
+   becomes writable for the first time (at this point you know that you may
+   write to it with the expectation of success).  The implied higher-level
+   events are:
+
+   +----------------------+----------------------------------------+
+   | Event                | Description                            |
+   +======================+========================================+
+   | ``handle_connect()`` | Implied by the first read or write     |
+   |                      | event                                  |
+   +----------------------+----------------------------------------+
+   | ``handle_close()``   | Implied by a read event with no data   |
+   |                      | available                              |
+   +----------------------+----------------------------------------+
+   | ``handle_accepted()``| Implied by a read event on a listening |
+   |                      | socket                                 |
+   +----------------------+----------------------------------------+
+
+   During asynchronous processing, each mapped channel's :meth:`readable` and
+   :meth:`writable` methods are used to determine whether the channel's socket
+   should be added to the list of channels :c:func:`select`\ ed or
+   :c:func:`poll`\ ed for read and write events.
+
+   Thus, the set of channel events is larger than the basic socket events.  The
+   full set of methods that can be overridden in your subclass follows:
+
+
+   .. method:: handle_read()
+
+      Called when the asynchronous loop detects that a :meth:`read` call on the
+      channel's socket will succeed.
+
+
+   .. method:: handle_write()
+
+      Called when the asynchronous loop detects that a writable socket can be
+      written.  Often this method will implement the necessary buffering for
+      performance.  For example::
+
+         def handle_write(self):
+             sent = self.send(self.buffer)
+             self.buffer = self.buffer[sent:]
+
+
+   .. method:: handle_expt()
+
+      Called when there is out of band (OOB) data for a socket connection.  This
+      will almost never happen, as OOB is tenuously supported and rarely used.
+
+
+   .. method:: handle_connect()
+
+      Called when the active opener's socket actually makes a connection.  Might
+      send a "welcome" banner, or initiate a protocol negotiation with the
+      remote endpoint, for example.
+
+
+   .. method:: handle_close()
+
+      Called when the socket is closed.
+
+
+   .. method:: handle_error()
+
+      Called when an exception is raised and not otherwise handled.  The default
+      version prints a condensed traceback.
+
+
+   .. method:: handle_accept()
+
+      Called on listening channels (passive openers) when a connection can be
+      established with a new remote endpoint that has issued a :meth:`connect`
+      call for the local endpoint. Deprecated in version 3.2; use
+      :meth:`handle_accepted` instead.
+
+      .. deprecated:: 3.2
+
+
+   .. method:: handle_accepted(sock, addr)
+
+      Called on listening channels (passive openers) when a connection has been
+      established with a new remote endpoint that has issued a :meth:`connect`
+      call for the local endpoint.  *sock* is a *new* socket object usable to
+      send and receive data on the connection, and *addr* is the address
+      bound to the socket on the other end of the connection.
+
+      .. versionadded:: 3.2
+
+
+   .. method:: readable()
+
+      Called each time around the asynchronous loop to determine whether a
+      channel's socket should be added to the list on which read events can
+      occur.  The default method simply returns ``True``, indicating that by
+      default, all channels will be interested in read events.
+
+
+   .. method:: writable()
+
+      Called each time around the asynchronous loop to determine whether a
+      channel's socket should be added to the list on which write events can
+      occur.  The default method simply returns ``True``, indicating that by
+      default, all channels will be interested in write events.
+
+
+   In addition, each channel delegates or extends many of the socket methods.
+   Most of these are nearly identical to their socket partners.
+
+
+   .. method:: create_socket(family=socket.AF_INET, type=socket.SOCK_STREAM)
+
+      This is identical to the creation of a normal socket, and will use the
+      same options for creation.  Refer to the :mod:`socket` documentation for
+      information on creating sockets.
+
+      .. versionchanged:: 3.3
+         *family* and *type* arguments can be omitted.
+
+
+   .. method:: connect(address)
+
+      As with the normal socket object, *address* is a tuple with the first
+      element the host to connect to, and the second the port number.
+
+
+   .. method:: send(data)
+
+      Send *data* to the remote end-point of the socket.
+
+
+   .. method:: recv(buffer_size)
+
+      Read at most *buffer_size* bytes from the socket's remote end-point.  An
+      empty bytes object implies that the channel has been closed from the
+      other end.
+
+      Note that :meth:`recv` may raise :exc:`BlockingIOError` , even though
+      :func:`select.select` or :func:`select.poll` has reported the socket
+      ready for reading.
+
+
+   .. method:: listen(backlog)
+
+      Listen for connections made to the socket.  The *backlog* argument
+      specifies the maximum number of queued connections and should be at least
+      1; the maximum value is system-dependent (usually 5).
+
+
+   .. method:: bind(address)
+
+      Bind the socket to *address*.  The socket must not already be bound.  (The
+      format of *address* depends on the address family --- refer to the
+      :mod:`socket` documentation for more information.)  To mark
+      the socket as re-usable (setting the :const:`SO_REUSEADDR` option), call
+      the :class:`dispatcher` object's :meth:`set_reuse_addr` method.
+
+
+   .. method:: accept()
+
+      Accept a connection.  The socket must be bound to an address and listening
+      for connections.  The return value can be either ``None`` or a pair
+      ``(conn, address)`` where *conn* is a *new* socket object usable to send
+      and receive data on the connection, and *address* is the address bound to
+      the socket on the other end of the connection.
+      When ``None`` is returned it means the connection didn't take place, in
+      which case the server should just ignore this event and keep listening
+      for further incoming connections.
+
+
+   .. method:: close()
+
+      Close the socket.  All future operations on the socket object will fail.
+      The remote end-point will receive no more data (after queued data is
+      flushed).  Sockets are automatically closed when they are
+      garbage-collected.
+
+
+.. class:: dispatcher_with_send()
+
+   A :class:`dispatcher` subclass which adds simple buffered output capability,
+   useful for simple clients. For more sophisticated usage use
+   :class:`asynchat.async_chat`.
+
+.. class:: file_dispatcher()
+
+   A file_dispatcher takes a file descriptor or :term:`file object` along
+   with an optional map argument and wraps it for use with the :c:func:`poll`
+   or :c:func:`loop` functions.  If provided a file object or anything with a
+   :c:func:`fileno` method, that method will be called and passed to the
+   :class:`file_wrapper` constructor.
+
+   .. availability:: Unix.
+
+.. class:: file_wrapper()
+
+   A file_wrapper takes an integer file descriptor and calls :func:`os.dup` to
+   duplicate the handle so that the original handle may be closed independently
+   of the file_wrapper.  This class implements sufficient methods to emulate a
+   socket for use by the :class:`file_dispatcher` class.
+
+   .. availability:: Unix.
+
+
+.. _asyncore-example-1:
+
+asyncore Example basic HTTP client
+----------------------------------
+
+Here is a very basic HTTP client that uses the :class:`dispatcher` class to
+implement its socket handling::
+
+   import asyncore
+
+   class HTTPClient(asyncore.dispatcher):
+
+       def __init__(self, host, path):
+           asyncore.dispatcher.__init__(self)
+           self.create_socket()
+           self.connect( (host, 80) )
+           self.buffer = bytes('GET %s HTTP/1.0\r\nHost: %s\r\n\r\n' %
+                               (path, host), 'ascii')
+
+       def handle_connect(self):
+           pass
+
+       def handle_close(self):
+           self.close()
+
+       def handle_read(self):
+           print(self.recv(8192))
+
+       def writable(self):
+           return (len(self.buffer) > 0)
+
+       def handle_write(self):
+           sent = self.send(self.buffer)
+           self.buffer = self.buffer[sent:]
+
+
+   client = HTTPClient('www.python.org', '/')
+   asyncore.loop()
+
+.. _asyncore-example-2:
+
+asyncore Example basic echo server
+----------------------------------
+
+Here is a basic echo server that uses the :class:`dispatcher` class to accept
+connections and dispatches the incoming connections to a handler::
+
+    import asyncore
+
+    class EchoHandler(asyncore.dispatcher_with_send):
+
+        def handle_read(self):
+            data = self.recv(8192)
+            if data:
+                self.send(data)
+
+    class EchoServer(asyncore.dispatcher):
+
+        def __init__(self, host, port):
+            asyncore.dispatcher.__init__(self)
+            self.create_socket()
+            self.set_reuse_addr()
+            self.bind((host, port))
+            self.listen(5)
+
+        def handle_accepted(self, sock, addr):
+            print('Incoming connection from %s' % repr(addr))
+            handler = EchoHandler(sock)
+
+    server = EchoServer('localhost', 8080)
+    asyncore.loop()
diff --git a/Doc/library/email.rst b/Doc/library/email.rst
index 816fae9..5eebcd9 100644
--- a/Doc/library/email.rst
+++ b/Doc/library/email.rst
@@ -147,3 +147,6 @@ Legacy API:
    Module :mod:`mailbox`
       Tools for creating, reading, and managing collections of messages on disk
       using a variety standard formats.
+
+   Module :mod:`smtpd`
+      SMTP server framework (primarily useful for testing)
diff --git a/Doc/library/internet.rst b/Doc/library/internet.rst
index 65693c9..e745dd1 100644
--- a/Doc/library/internet.rst
+++ b/Doc/library/internet.rst
@@ -35,6 +35,7 @@ is currently supported on most popular platforms.  Here is an overview:
    imaplib.rst
    nntplib.rst
    smtplib.rst
+   smtpd.rst
    telnetlib.rst
    uuid.rst
    socketserver.rst
diff --git a/Doc/library/ipc.rst b/Doc/library/ipc.rst
index 4849c82..b88a174 100644
--- a/Doc/library/ipc.rst
+++ b/Doc/library/ipc.rst
@@ -22,5 +22,7 @@ The list of modules described in this chapter is:
    ssl.rst
    select.rst
    selectors.rst
+   asyncore.rst
+   asynchat.rst
    signal.rst
    mmap.rst
diff --git a/Doc/library/smtpd.rst b/Doc/library/smtpd.rst
new file mode 100644
index 0000000..611411d
--- /dev/null
+++ b/Doc/library/smtpd.rst
@@ -0,0 +1,264 @@
+:mod:`smtpd` --- SMTP Server
+============================
+
+.. module:: smtpd
+   :synopsis: A SMTP server implementation in Python.
+
+.. moduleauthor:: Barry Warsaw <barry@python.org>
+.. sectionauthor:: Moshe Zadka <moshez@moshez.org>
+
+**Source code:** :source:`Lib/smtpd.py`
+
+--------------
+
+This module offers several classes to implement SMTP (email) servers.
+
+.. deprecated:: 3.6
+   The `aiosmtpd <https://aiosmtpd.readthedocs.io/>`_ package is a recommended
+   replacement for this module.  It is based on :mod:`asyncio` and provides a
+   more straightforward API.
+
+Several server implementations are present; one is a generic
+do-nothing implementation, which can be overridden, while the other two offer
+specific mail-sending strategies.
+
+Additionally the SMTPChannel may be extended to implement very specific
+interaction behaviour with SMTP clients.
+
+The code supports :RFC:`5321`, plus the :rfc:`1870` SIZE and :rfc:`6531`
+SMTPUTF8 extensions.
+
+
+SMTPServer Objects
+------------------
+
+
+.. class:: SMTPServer(localaddr, remoteaddr, data_size_limit=33554432,\
+                      map=None, enable_SMTPUTF8=False, decode_data=False)
+
+   Create a new :class:`SMTPServer` object, which binds to local address
+   *localaddr*.  It will treat *remoteaddr* as an upstream SMTP relayer.  Both
+   *localaddr* and *remoteaddr* should be a :ref:`(host, port) <host_port>`
+   tuple.  The object inherits from :class:`asyncore.dispatcher`, and so will
+   insert itself into :mod:`asyncore`'s event loop on instantiation.
+
+   *data_size_limit* specifies the maximum number of bytes that will be
+   accepted in a ``DATA`` command.  A value of ``None`` or ``0`` means no
+   limit.
+
+   *map* is the socket map to use for connections (an initially empty
+   dictionary is a suitable value).  If not specified the :mod:`asyncore`
+   global socket map is used.
+
+   *enable_SMTPUTF8* determines whether the ``SMTPUTF8`` extension (as defined
+   in :RFC:`6531`) should be enabled.  The default is ``False``.
+   When ``True``, ``SMTPUTF8`` is accepted as a parameter to the ``MAIL``
+   command and when present is passed to :meth:`process_message` in the
+   ``kwargs['mail_options']`` list.  *decode_data* and *enable_SMTPUTF8*
+   cannot be set to ``True`` at the same time.
+
+   *decode_data* specifies whether the data portion of the SMTP transaction
+   should be decoded using UTF-8.  When *decode_data* is ``False`` (the
+   default), the server advertises the ``8BITMIME``
+   extension (:rfc:`6152`), accepts the ``BODY=8BITMIME`` parameter to
+   the ``MAIL`` command, and when present passes it to :meth:`process_message`
+   in the ``kwargs['mail_options']`` list. *decode_data* and *enable_SMTPUTF8*
+   cannot be set to ``True`` at the same time.
+
+   .. method:: process_message(peer, mailfrom, rcpttos, data, **kwargs)
+
+      Raise a :exc:`NotImplementedError` exception. Override this in subclasses to
+      do something useful with this message. Whatever was passed in the
+      constructor as *remoteaddr* will be available as the :attr:`_remoteaddr`
+      attribute. *peer* is the remote host's address, *mailfrom* is the envelope
+      originator, *rcpttos* are the envelope recipients and *data* is a string
+      containing the contents of the e-mail (which should be in :rfc:`5321`
+      format).
+
+      If the *decode_data* constructor keyword is set to ``True``, the *data*
+      argument will be a unicode string.  If it is set to ``False``, it
+      will be a bytes object.
+
+      *kwargs* is a dictionary containing additional information. It is empty
+      if ``decode_data=True`` was given as an init argument, otherwise
+      it contains the following keys:
+
+          *mail_options*:
+             a list of all received parameters to the ``MAIL``
+             command (the elements are uppercase strings; example:
+             ``['BODY=8BITMIME', 'SMTPUTF8']``).
+
+          *rcpt_options*:
+             same as *mail_options* but for the ``RCPT`` command.
+             Currently no ``RCPT TO`` options are supported, so for now
+             this will always be an empty list.
+
+      Implementations of ``process_message`` should use the ``**kwargs``
+      signature to accept arbitrary keyword arguments, since future feature
+      enhancements may add keys to the kwargs dictionary.
+
+      Return ``None`` to request a normal ``250 Ok`` response; otherwise
+      return the desired response string in :RFC:`5321` format.
+
+   .. attribute:: channel_class
+
+      Override this in subclasses to use a custom :class:`SMTPChannel` for
+      managing SMTP clients.
+
+   .. versionadded:: 3.4
+      The *map* constructor argument.
+
+   .. versionchanged:: 3.5
+      *localaddr* and *remoteaddr* may now contain IPv6 addresses.
+
+   .. versionadded:: 3.5
+      The *decode_data* and *enable_SMTPUTF8* constructor parameters, and the
+      *kwargs* parameter to :meth:`process_message` when *decode_data* is
+      ``False``.
+
+   .. versionchanged:: 3.6
+      *decode_data* is now ``False`` by default.
+
+
+DebuggingServer Objects
+-----------------------
+
+
+.. class:: DebuggingServer(localaddr, remoteaddr)
+
+   Create a new debugging server.  Arguments are as per :class:`SMTPServer`.
+   Messages will be discarded, and printed on stdout.
+
+
+PureProxy Objects
+-----------------
+
+
+.. class:: PureProxy(localaddr, remoteaddr)
+
+   Create a new pure proxy server. Arguments are as per :class:`SMTPServer`.
+   Everything will be relayed to *remoteaddr*.  Note that running this has a good
+   chance to make you into an open relay, so please be careful.
+
+
+SMTPChannel Objects
+-------------------
+
+.. class:: SMTPChannel(server, conn, addr, data_size_limit=33554432,\
+                       map=None, enable_SMTPUTF8=False, decode_data=False)
+
+   Create a new :class:`SMTPChannel` object which manages the communication
+   between the server and a single SMTP client.
+
+   *conn* and *addr* are as per the instance variables described below.
+
+   *data_size_limit* specifies the maximum number of bytes that will be
+   accepted in a ``DATA`` command.  A value of ``None`` or ``0`` means no
+   limit.
+
+   *enable_SMTPUTF8* determines whether the ``SMTPUTF8`` extension (as defined
+   in :RFC:`6531`) should be enabled.  The default is ``False``.
+   *decode_data* and *enable_SMTPUTF8* cannot be set to ``True`` at the same
+   time.
+
+   A dictionary can be specified in *map* to avoid using a global socket map.
+
+   *decode_data* specifies whether the data portion of the SMTP transaction
+   should be decoded using UTF-8.  The default is ``False``.
+   *decode_data* and *enable_SMTPUTF8* cannot be set to ``True`` at the same
+   time.
+
+   To use a custom SMTPChannel implementation you need to override the
+   :attr:`SMTPServer.channel_class` of your :class:`SMTPServer`.
+
+   .. versionchanged:: 3.5
+      The *decode_data* and *enable_SMTPUTF8* parameters were added.
+
+   .. versionchanged:: 3.6
+      *decode_data* is now ``False`` by default.
+
+   The :class:`SMTPChannel` has the following instance variables:
+
+   .. attribute:: smtp_server
+
+      Holds the :class:`SMTPServer` that spawned this channel.
+
+   .. attribute:: conn
+
+      Holds the socket object connecting to the client.
+
+   .. attribute:: addr
+
+      Holds the address of the client, the second value returned by
+      :func:`socket.accept <socket.socket.accept>`
+
+   .. attribute:: received_lines
+
+      Holds a list of the line strings (decoded using UTF-8) received from
+      the client. The lines have their ``"\r\n"`` line ending translated to
+      ``"\n"``.
+
+   .. attribute:: smtp_state
+
+      Holds the current state of the channel. This will be either
+      :attr:`COMMAND` initially and then :attr:`DATA` after the client sends
+      a "DATA" line.
+
+   .. attribute:: seen_greeting
+
+      Holds a string containing the greeting sent by the client in its "HELO".
+
+   .. attribute:: mailfrom
+
+      Holds a string containing the address identified in the "MAIL FROM:" line
+      from the client.
+
+   .. attribute:: rcpttos
+
+      Holds a list of strings containing the addresses identified in the
+      "RCPT TO:" lines from the client.
+
+   .. attribute:: received_data
+
+      Holds a string containing all of the data sent by the client during the
+      DATA state, up to but not including the terminating ``"\r\n.\r\n"``.
+
+   .. attribute:: fqdn
+
+      Holds the fully-qualified domain name of the server as returned by
+      :func:`socket.getfqdn`.
+
+   .. attribute:: peer
+
+      Holds the name of the client peer as returned by ``conn.getpeername()``
+      where ``conn`` is :attr:`conn`.
+
+   The :class:`SMTPChannel` operates by invoking methods named ``smtp_<command>``
+   upon reception of a command line from the client. Built into the base
+   :class:`SMTPChannel` class are methods for handling the following commands
+   (and responding to them appropriately):
+
+   ======== ===================================================================
+   Command  Action taken
+   ======== ===================================================================
+   HELO     Accepts the greeting from the client and stores it in
+            :attr:`seen_greeting`.  Sets server to base command mode.
+   EHLO     Accepts the greeting from the client and stores it in
+            :attr:`seen_greeting`.  Sets server to extended command mode.
+   NOOP     Takes no action.
+   QUIT     Closes the connection cleanly.
+   MAIL     Accepts the "MAIL FROM:" syntax and stores the supplied address as
+            :attr:`mailfrom`.  In extended command mode, accepts the
+            :rfc:`1870` SIZE attribute and responds appropriately based on the
+            value of *data_size_limit*.
+   RCPT     Accepts the "RCPT TO:" syntax and stores the supplied addresses in
+            the :attr:`rcpttos` list.
+   RSET     Resets the :attr:`mailfrom`, :attr:`rcpttos`, and
+            :attr:`received_data`, but not the greeting.
+   DATA     Sets the internal state to :attr:`DATA` and stores remaining lines
+            from the client in :attr:`received_data` until the terminator
+            ``"\r\n.\r\n"`` is received.
+   HELP     Returns minimal information on command syntax
+   VRFY     Returns code 252 (the server doesn't know if the address is valid)
+   EXPN     Reports that the command is not implemented.
+   ======== ===================================================================
diff --git a/Doc/library/socketserver.rst b/Doc/library/socketserver.rst
index 8aa72bd..b65a3e8 100644
--- a/Doc/library/socketserver.rst
+++ b/Doc/library/socketserver.rst
@@ -176,7 +176,7 @@ partially finished requests and to use :mod:`selectors` to decide which
 request to work on next (or whether to handle a new incoming request).  This is
 particularly important for stream services where each client can potentially be
 connected for a long time (if threads or subprocesses cannot be used).  See
-:mod:`asyncio` for another way to manage this.
+:mod:`asyncore` for another way to manage this.
 
 .. XXX should data and methods be intermingled, or separate?
    how should the distinction between class and instance variables be drawn?
diff --git a/Doc/license.rst b/Doc/license.rst
index 1d086b6..cd03411 100644
--- a/Doc/license.rst
+++ b/Doc/license.rst
@@ -383,6 +383,33 @@ Project, http://www.wide.ad.jp/. ::
    SUCH DAMAGE.
 
 
+Asynchronous socket services
+----------------------------
+
+The :mod:`asynchat` and :mod:`asyncore` modules contain the following notice::
+
+   Copyright 1996 by Sam Rushing
+
+                           All Rights Reserved
+
+   Permission to use, copy, modify, and distribute this software and
+   its documentation for any purpose and without fee is hereby
+   granted, provided that the above copyright notice appear in all
+   copies and that both that copyright notice and this permission
+   notice appear in supporting documentation, and that the name of Sam
+   Rushing not be used in advertising or publicity pertaining to
+   distribution of the software without specific, written prior
+   permission.
+
+   SAM RUSHING DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+   INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN
+   NO EVENT SHALL SAM RUSHING BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+   CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+   OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
+   NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+   CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+
 Cookie management
 -----------------
 
diff --git a/Doc/whatsnew/3.11.rst b/Doc/whatsnew/3.11.rst
index b06d8d4..a570864 100644
--- a/Doc/whatsnew/3.11.rst
+++ b/Doc/whatsnew/3.11.rst
@@ -518,15 +518,6 @@ Removed
 
   (Contributed by Hugo van Kemenade in :issue:`45320`.)
 
-* Remove the ``asyncore`` and ``asynchat`` modules, deprecated in Python 3.6:
-  use the :mod:`asyncio` module instead.
-  (Contributed by Victor Stinner in :issue:`28533`.)
-
-* Remove the ``smtpd`` module, deprecated in Python 3.6: the `aiosmtpd
-  <https://aiosmtpd.readthedocs.io/>`__ module can be used instead, it is based
-  on asyncio.
-  (Contributed by Victor Stinner in :issue:`28533`.)
-
 
 Porting to Python 3.11
 ======================
diff --git a/Lib/test/support/_asynchat.py b/Lib/asynchat.py
index 941cc1d..de26ffa 100644
--- a/Lib/test/support/_asynchat.py
+++ b/Lib/asynchat.py
@@ -45,9 +45,17 @@ command will be accumulated (using your own 'collect_incoming_data'
 method) up to the terminator, and then control will be returned to
 you - by calling your self.found_terminator() method.
 """
-from test.support import _asyncore as asyncore
+import asyncore
 from collections import deque
 
+from warnings import warn
+warn(
+    'The asynchat module is deprecated. '
+    'The recommended replacement is asyncio',
+    DeprecationWarning,
+    stacklevel=2)
+
+
 
 class async_chat(asyncore.dispatcher):
     """This is an abstract class.  You must derive from this class, and add
diff --git a/Lib/test/support/_asyncore.py b/Lib/asyncore.py
index 7863efa..b1eea4b 100644
--- a/Lib/test/support/_asyncore.py
+++ b/Lib/asyncore.py
@@ -57,6 +57,12 @@ from errno import EALREADY, EINPROGRESS, EWOULDBLOCK, ECONNRESET, EINVAL, \
      ENOTCONN, ESHUTDOWN, EISCONN, EBADF, ECONNABORTED, EPIPE, EAGAIN, \
      errorcode
 
+warnings.warn(
+    'The asyncore module is deprecated. '
+    'The recommended replacement is asyncio',
+    DeprecationWarning,
+    stacklevel=2)
+
 
 _DISCONNECTED = frozenset({ECONNRESET, ENOTCONN, ESHUTDOWN, ECONNABORTED, EPIPE,
                            EBADF})
diff --git a/Lib/test/support/_smtpd.py b/Lib/smtpd.py
index 0e37d08..1cd004f 100755
--- a/Lib/test/support/_smtpd.py
+++ b/Lib/smtpd.py
@@ -80,13 +80,22 @@ import collections
 from warnings import warn
 from email._header_value_parser import get_addr_spec, get_angle_addr
 
-from test.support import _asyncore as asyncore
-from test.support import _asynchat as asynchat
-
 __all__ = [
     "SMTPChannel", "SMTPServer", "DebuggingServer", "PureProxy",
 ]
 
+warn(
+    'The smtpd module is deprecated and unmaintained.  Please see aiosmtpd '
+    '(https://aiosmtpd.readthedocs.io/) for the recommended replacement.',
+    DeprecationWarning,
+    stacklevel=2)
+
+
+# These are imported after the above warning so that users get the correct
+# deprecation warning.
+import asyncore
+import asynchat
+
 
 program = sys.argv[0]
 __version__ = 'Python SMTP proxy version 0.3'
@@ -179,6 +188,128 @@ class SMTPChannel(asynchat.async_chat):
         self.received_lines = []
 
 
+    # properties for backwards-compatibility
+    @property
+    def __server(self):
+        warn("Access to __server attribute on SMTPChannel is deprecated, "
+            "use 'smtp_server' instead", DeprecationWarning, 2)
+        return self.smtp_server
+    @__server.setter
+    def __server(self, value):
+        warn("Setting __server attribute on SMTPChannel is deprecated, "
+            "set 'smtp_server' instead", DeprecationWarning, 2)
+        self.smtp_server = value
+
+    @property
+    def __line(self):
+        warn("Access to __line attribute on SMTPChannel is deprecated, "
+            "use 'received_lines' instead", DeprecationWarning, 2)
+        return self.received_lines
+    @__line.setter
+    def __line(self, value):
+        warn("Setting __line attribute on SMTPChannel is deprecated, "
+            "set 'received_lines' instead", DeprecationWarning, 2)
+        self.received_lines = value
+
+    @property
+    def __state(self):
+        warn("Access to __state attribute on SMTPChannel is deprecated, "
+            "use 'smtp_state' instead", DeprecationWarning, 2)
+        return self.smtp_state
+    @__state.setter
+    def __state(self, value):
+        warn("Setting __state attribute on SMTPChannel is deprecated, "
+            "set 'smtp_state' instead", DeprecationWarning, 2)
+        self.smtp_state = value
+
+    @property
+    def __greeting(self):
+        warn("Access to __greeting attribute on SMTPChannel is deprecated, "
+            "use 'seen_greeting' instead", DeprecationWarning, 2)
+        return self.seen_greeting
+    @__greeting.setter
+    def __greeting(self, value):
+        warn("Setting __greeting attribute on SMTPChannel is deprecated, "
+            "set 'seen_greeting' instead", DeprecationWarning, 2)
+        self.seen_greeting = value
+
+    @property
+    def __mailfrom(self):
+        warn("Access to __mailfrom attribute on SMTPChannel is deprecated, "
+            "use 'mailfrom' instead", DeprecationWarning, 2)
+        return self.mailfrom
+    @__mailfrom.setter
+    def __mailfrom(self, value):
+        warn("Setting __mailfrom attribute on SMTPChannel is deprecated, "
+            "set 'mailfrom' instead", DeprecationWarning, 2)
+        self.mailfrom = value
+
+    @property
+    def __rcpttos(self):
+        warn("Access to __rcpttos attribute on SMTPChannel is deprecated, "
+            "use 'rcpttos' instead", DeprecationWarning, 2)
+        return self.rcpttos
+    @__rcpttos.setter
+    def __rcpttos(self, value):
+        warn("Setting __rcpttos attribute on SMTPChannel is deprecated, "
+            "set 'rcpttos' instead", DeprecationWarning, 2)
+        self.rcpttos = value
+
+    @property
+    def __data(self):
+        warn("Access to __data attribute on SMTPChannel is deprecated, "
+            "use 'received_data' instead", DeprecationWarning, 2)
+        return self.received_data
+    @__data.setter
+    def __data(self, value):
+        warn("Setting __data attribute on SMTPChannel is deprecated, "
+            "set 'received_data' instead", DeprecationWarning, 2)
+        self.received_data = value
+
+    @property
+    def __fqdn(self):
+        warn("Access to __fqdn attribute on SMTPChannel is deprecated, "
+            "use 'fqdn' instead", DeprecationWarning, 2)
+        return self.fqdn
+    @__fqdn.setter
+    def __fqdn(self, value):
+        warn("Setting __fqdn attribute on SMTPChannel is deprecated, "
+            "set 'fqdn' instead", DeprecationWarning, 2)
+        self.fqdn = value
+
+    @property
+    def __peer(self):
+        warn("Access to __peer attribute on SMTPChannel is deprecated, "
+            "use 'peer' instead", DeprecationWarning, 2)
+        return self.peer
+    @__peer.setter
+    def __peer(self, value):
+        warn("Setting __peer attribute on SMTPChannel is deprecated, "
+            "set 'peer' instead", DeprecationWarning, 2)
+        self.peer = value
+
+    @property
+    def __conn(self):
+        warn("Access to __conn attribute on SMTPChannel is deprecated, "
+            "use 'conn' instead", DeprecationWarning, 2)
+        return self.conn
+    @__conn.setter
+    def __conn(self, value):
+        warn("Setting __conn attribute on SMTPChannel is deprecated, "
+            "set 'conn' instead", DeprecationWarning, 2)
+        self.conn = value
+
+    @property
+    def __addr(self):
+        warn("Access to __addr attribute on SMTPChannel is deprecated, "
+            "use 'addr' instead", DeprecationWarning, 2)
+        return self.addr
+    @__addr.setter
+    def __addr(self, value):
+        warn("Setting __addr attribute on SMTPChannel is deprecated, "
+            "set 'addr' instead", DeprecationWarning, 2)
+        self.addr = value
+
     # Overrides base class for convenience.
     def push(self, msg):
         asynchat.async_chat.push(self, bytes(
diff --git a/Lib/test/libregrtest/save_env.py b/Lib/test/libregrtest/save_env.py
index 17dda99..60c9be2 100644
--- a/Lib/test/libregrtest/save_env.py
+++ b/Lib/test/libregrtest/save_env.py
@@ -52,7 +52,7 @@ class saved_test_environment:
 
     resources = ('sys.argv', 'cwd', 'sys.stdin', 'sys.stdout', 'sys.stderr',
                  'os.environ', 'sys.path', 'sys.path_hooks', '__import__',
-                 'warnings.filters',
+                 'warnings.filters', 'asyncore.socket_map',
                  'logging._handlers', 'logging._handlerList', 'sys.gettrace',
                  'sys.warnoptions',
                  # multiprocessing.process._cleanup() may release ref
@@ -160,6 +160,16 @@ class saved_test_environment:
         warnings.filters = saved_filters[1]
         warnings.filters[:] = saved_filters[2]
 
+    def get_asyncore_socket_map(self):
+        asyncore = sys.modules.get('asyncore')
+        # XXX Making a copy keeps objects alive until __exit__ gets called.
+        return asyncore and asyncore.socket_map.copy() or {}
+    def restore_asyncore_socket_map(self, saved_map):
+        asyncore = sys.modules.get('asyncore')
+        if asyncore is not None:
+            asyncore.close_all(ignore_all=True)
+            asyncore.socket_map.update(saved_map)
+
     def get_shutil_archive_formats(self):
         shutil = self.try_get_module('shutil')
         # we could call get_archives_formats() but that only returns the
diff --git a/Lib/test/mock_socket.py b/Lib/test/mock_socket.py
index 9788d58..c7abddc 100644
--- a/Lib/test/mock_socket.py
+++ b/Lib/test/mock_socket.py
@@ -1,4 +1,4 @@
-"""Mock socket module used by the smtplib tests.
+"""Mock socket module used by the smtpd and smtplib tests.
 """
 
 # imported for _GLOBAL_DEFAULT_TIMEOUT
@@ -33,7 +33,7 @@ class MockFile:
 
 
 class MockSocket:
-    """Mock socket object used by smtplib tests.
+    """Mock socket object used by smtpd and smtplib tests.
     """
     def __init__(self, family=None):
         global _reply_data
diff --git a/Lib/test/test_asynchat.py b/Lib/test/test_asynchat.py
new file mode 100644
index 0000000..973ac1f
--- /dev/null
+++ b/Lib/test/test_asynchat.py
@@ -0,0 +1,292 @@
+# test asynchat
+
+from test import support
+from test.support import socket_helper
+from test.support import threading_helper
+
+import errno
+import socket
+import sys
+import threading
+import time
+import unittest
+import unittest.mock
+
+import warnings
+with warnings.catch_warnings():
+    warnings.simplefilter('ignore', DeprecationWarning)
+    import asynchat
+    import asyncore
+
+HOST = socket_helper.HOST
+SERVER_QUIT = b'QUIT\n'
+
+
+class echo_server(threading.Thread):
+    # parameter to determine the number of bytes passed back to the
+    # client each send
+    chunk_size = 1
+
+    def __init__(self, event):
+        threading.Thread.__init__(self)
+        self.event = event
+        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        self.port = socket_helper.bind_port(self.sock)
+        # This will be set if the client wants us to wait before echoing
+        # data back.
+        self.start_resend_event = None
+
+    def run(self):
+        self.sock.listen()
+        self.event.set()
+        conn, client = self.sock.accept()
+        self.buffer = b""
+        # collect data until quit message is seen
+        while SERVER_QUIT not in self.buffer:
+            data = conn.recv(1)
+            if not data:
+                break
+            self.buffer = self.buffer + data
+
+        # remove the SERVER_QUIT message
+        self.buffer = self.buffer.replace(SERVER_QUIT, b'')
+
+        if self.start_resend_event:
+            self.start_resend_event.wait()
+
+        # re-send entire set of collected data
+        try:
+            # this may fail on some tests, such as test_close_when_done,
+            # since the client closes the channel when it's done sending
+            while self.buffer:
+                n = conn.send(self.buffer[:self.chunk_size])
+                time.sleep(0.001)
+                self.buffer = self.buffer[n:]
+        except:
+            pass
+
+        conn.close()
+        self.sock.close()
+
+class echo_client(asynchat.async_chat):
+
+    def __init__(self, terminator, server_port):
+        asynchat.async_chat.__init__(self)
+        self.contents = []
+        self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
+        self.connect((HOST, server_port))
+        self.set_terminator(terminator)
+        self.buffer = b""
+
+    def handle_connect(self):
+        pass
+
+    if sys.platform == 'darwin':
+        # select.poll returns a select.POLLHUP at the end of the tests
+        # on darwin, so just ignore it
+        def handle_expt(self):
+            pass
+
+    def collect_incoming_data(self, data):
+        self.buffer += data
+
+    def found_terminator(self):
+        self.contents.append(self.buffer)
+        self.buffer = b""
+
+def start_echo_server():
+    event = threading.Event()
+    s = echo_server(event)
+    s.start()
+    event.wait()
+    event.clear()
+    time.sleep(0.01)   # Give server time to start accepting.
+    return s, event
+
+
+class TestAsynchat(unittest.TestCase):
+    usepoll = False
+
+    def setUp(self):
+        self._threads = threading_helper.threading_setup()
+
+    def tearDown(self):
+        threading_helper.threading_cleanup(*self._threads)
+
+    def line_terminator_check(self, term, server_chunk):
+        event = threading.Event()
+        s = echo_server(event)
+        s.chunk_size = server_chunk
+        s.start()
+        event.wait()
+        event.clear()
+        time.sleep(0.01)   # Give server time to start accepting.
+        c = echo_client(term, s.port)
+        c.push(b"hello ")
+        c.push(b"world" + term)
+        c.push(b"I'm not dead yet!" + term)
+        c.push(SERVER_QUIT)
+        asyncore.loop(use_poll=self.usepoll, count=300, timeout=.01)
+        threading_helper.join_thread(s)
+
+        self.assertEqual(c.contents, [b"hello world", b"I'm not dead yet!"])
+
+    # the line terminator tests below check receiving variously-sized
+    # chunks back from the server in order to exercise all branches of
+    # async_chat.handle_read
+
+    def test_line_terminator1(self):
+        # test one-character terminator
+        for l in (1, 2, 3):
+            self.line_terminator_check(b'\n', l)
+
+    def test_line_terminator2(self):
+        # test two-character terminator
+        for l in (1, 2, 3):
+            self.line_terminator_check(b'\r\n', l)
+
+    def test_line_terminator3(self):
+        # test three-character terminator
+        for l in (1, 2, 3):
+            self.line_terminator_check(b'qqq', l)
+
+    def numeric_terminator_check(self, termlen):
+        # Try reading a fixed number of bytes
+        s, event = start_echo_server()
+        c = echo_client(termlen, s.port)
+        data = b"hello world, I'm not dead yet!\n"
+        c.push(data)
+        c.push(SERVER_QUIT)
+        asyncore.loop(use_poll=self.usepoll, count=300, timeout=.01)
+        threading_helper.join_thread(s)
+
+        self.assertEqual(c.contents, [data[:termlen]])
+
+    def test_numeric_terminator1(self):
+        # check that ints & longs both work (since type is
+        # explicitly checked in async_chat.handle_read)
+        self.numeric_terminator_check(1)
+
+    def test_numeric_terminator2(self):
+        self.numeric_terminator_check(6)
+
+    def test_none_terminator(self):
+        # Try reading a fixed number of bytes
+        s, event = start_echo_server()
+        c = echo_client(None, s.port)
+        data = b"hello world, I'm not dead yet!\n"
+        c.push(data)
+        c.push(SERVER_QUIT)
+        asyncore.loop(use_poll=self.usepoll, count=300, timeout=.01)
+        threading_helper.join_thread(s)
+
+        self.assertEqual(c.contents, [])
+        self.assertEqual(c.buffer, data)
+
+    def test_simple_producer(self):
+        s, event = start_echo_server()
+        c = echo_client(b'\n', s.port)
+        data = b"hello world\nI'm not dead yet!\n"
+        p = asynchat.simple_producer(data+SERVER_QUIT, buffer_size=8)
+        c.push_with_producer(p)
+        asyncore.loop(use_poll=self.usepoll, count=300, timeout=.01)
+        threading_helper.join_thread(s)
+
+        self.assertEqual(c.contents, [b"hello world", b"I'm not dead yet!"])
+
+    def test_string_producer(self):
+        s, event = start_echo_server()
+        c = echo_client(b'\n', s.port)
+        data = b"hello world\nI'm not dead yet!\n"
+        c.push_with_producer(data+SERVER_QUIT)
+        asyncore.loop(use_poll=self.usepoll, count=300, timeout=.01)
+        threading_helper.join_thread(s)
+
+        self.assertEqual(c.contents, [b"hello world", b"I'm not dead yet!"])
+
+    def test_empty_line(self):
+        # checks that empty lines are handled correctly
+        s, event = start_echo_server()
+        c = echo_client(b'\n', s.port)
+        c.push(b"hello world\n\nI'm not dead yet!\n")
+        c.push(SERVER_QUIT)
+        asyncore.loop(use_poll=self.usepoll, count=300, timeout=.01)
+        threading_helper.join_thread(s)
+
+        self.assertEqual(c.contents,
+                         [b"hello world", b"", b"I'm not dead yet!"])
+
+    def test_close_when_done(self):
+        s, event = start_echo_server()
+        s.start_resend_event = threading.Event()
+        c = echo_client(b'\n', s.port)
+        c.push(b"hello world\nI'm not dead yet!\n")
+        c.push(SERVER_QUIT)
+        c.close_when_done()
+        asyncore.loop(use_poll=self.usepoll, count=300, timeout=.01)
+
+        # Only allow the server to start echoing data back to the client after
+        # the client has closed its connection.  This prevents a race condition
+        # where the server echoes all of its data before we can check that it
+        # got any down below.
+        s.start_resend_event.set()
+        threading_helper.join_thread(s)
+
+        self.assertEqual(c.contents, [])
+        # the server might have been able to send a byte or two back, but this
+        # at least checks that it received something and didn't just fail
+        # (which could still result in the client not having received anything)
+        self.assertGreater(len(s.buffer), 0)
+
+    def test_push(self):
+        # Issue #12523: push() should raise a TypeError if it doesn't get
+        # a bytes string
+        s, event = start_echo_server()
+        c = echo_client(b'\n', s.port)
+        data = b'bytes\n'
+        c.push(data)
+        c.push(bytearray(data))
+        c.push(memoryview(data))
+        self.assertRaises(TypeError, c.push, 10)
+        self.assertRaises(TypeError, c.push, 'unicode')
+        c.push(SERVER_QUIT)
+        asyncore.loop(use_poll=self.usepoll, count=300, timeout=.01)
+        threading_helper.join_thread(s)
+        self.assertEqual(c.contents, [b'bytes', b'bytes', b'bytes'])
+
+
+class TestAsynchat_WithPoll(TestAsynchat):
+    usepoll = True
+
+
+class TestAsynchatMocked(unittest.TestCase):
+    def test_blockingioerror(self):
+        # Issue #16133: handle_read() must ignore BlockingIOError
+        sock = unittest.mock.Mock()
+        sock.recv.side_effect = BlockingIOError(errno.EAGAIN)
+
+        dispatcher = asynchat.async_chat()
+        dispatcher.set_socket(sock)
+        self.addCleanup(dispatcher.del_channel)
+
+        with unittest.mock.patch.object(dispatcher, 'handle_error') as error:
+            dispatcher.handle_read()
+        self.assertFalse(error.called)
+
+
+class TestHelperFunctions(unittest.TestCase):
+    def test_find_prefix_at_end(self):
+        self.assertEqual(asynchat.find_prefix_at_end("qwerty\r", "\r\n"), 1)
+        self.assertEqual(asynchat.find_prefix_at_end("qwertydkjf", "\r\n"), 0)
+
+
+class TestNotConnected(unittest.TestCase):
+    def test_disallow_negative_terminator(self):
+        # Issue #11259
+        client = asynchat.async_chat()
+        self.assertRaises(ValueError, client.set_terminator, -1)
+
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/Lib/test/test_asyncore.py b/Lib/test/test_asyncore.py
new file mode 100644
index 0000000..ecd1e12
--- /dev/null
+++ b/Lib/test/test_asyncore.py
@@ -0,0 +1,841 @@
+import unittest
+import select
+import os
+import socket
+import sys
+import time
+import errno
+import struct
+import threading
+
+from test import support
+from test.support import os_helper
+from test.support import socket_helper
+from test.support import threading_helper
+from test.support import warnings_helper
+from io import BytesIO
+
+if support.PGO:
+    raise unittest.SkipTest("test is not helpful for PGO")
+
+import warnings
+with warnings.catch_warnings():
+    warnings.simplefilter('ignore', DeprecationWarning)
+    import asyncore
+
+
+HAS_UNIX_SOCKETS = hasattr(socket, 'AF_UNIX')
+
+class dummysocket:
+    def __init__(self):
+        self.closed = False
+
+    def close(self):
+        self.closed = True
+
+    def fileno(self):
+        return 42
+
+class dummychannel:
+    def __init__(self):
+        self.socket = dummysocket()
+
+    def close(self):
+        self.socket.close()
+
+class exitingdummy:
+    def __init__(self):
+        pass
+
+    def handle_read_event(self):
+        raise asyncore.ExitNow()
+
+    handle_write_event = handle_read_event
+    handle_close = handle_read_event
+    handle_expt_event = handle_read_event
+
+class crashingdummy:
+    def __init__(self):
+        self.error_handled = False
+
+    def handle_read_event(self):
+        raise Exception()
+
+    handle_write_event = handle_read_event
+    handle_close = handle_read_event
+    handle_expt_event = handle_read_event
+
+    def handle_error(self):
+        self.error_handled = True
+
+# used when testing senders; just collects what it gets until newline is sent
+def capture_server(evt, buf, serv):
+    try:
+        serv.listen()
+        conn, addr = serv.accept()
+    except TimeoutError:
+        pass
+    else:
+        n = 200
+        start = time.monotonic()
+        while n > 0 and time.monotonic() - start < 3.0:
+            r, w, e = select.select([conn], [], [], 0.1)
+            if r:
+                n -= 1
+                data = conn.recv(10)
+                # keep everything except for the newline terminator
+                buf.write(data.replace(b'\n', b''))
+                if b'\n' in data:
+                    break
+            time.sleep(0.01)
+
+        conn.close()
+    finally:
+        serv.close()
+        evt.set()
+
+def bind_af_aware(sock, addr):
+    """Helper function to bind a socket according to its family."""
+    if HAS_UNIX_SOCKETS and sock.family == socket.AF_UNIX:
+        # Make sure the path doesn't exist.
+        os_helper.unlink(addr)
+        socket_helper.bind_unix_socket(sock, addr)
+    else:
+        sock.bind(addr)
+
+
+class HelperFunctionTests(unittest.TestCase):
+    def test_readwriteexc(self):
+        # Check exception handling behavior of read, write and _exception
+
+        # check that ExitNow exceptions in the object handler method
+        # bubbles all the way up through asyncore read/write/_exception calls
+        tr1 = exitingdummy()
+        self.assertRaises(asyncore.ExitNow, asyncore.read, tr1)
+        self.assertRaises(asyncore.ExitNow, asyncore.write, tr1)
+        self.assertRaises(asyncore.ExitNow, asyncore._exception, tr1)
+
+        # check that an exception other than ExitNow in the object handler
+        # method causes the handle_error method to get called
+        tr2 = crashingdummy()
+        asyncore.read(tr2)
+        self.assertEqual(tr2.error_handled, True)
+
+        tr2 = crashingdummy()
+        asyncore.write(tr2)
+        self.assertEqual(tr2.error_handled, True)
+
+        tr2 = crashingdummy()
+        asyncore._exception(tr2)
+        self.assertEqual(tr2.error_handled, True)
+
+    # asyncore.readwrite uses constants in the select module that
+    # are not present in Windows systems (see this thread:
+    # http://mail.python.org/pipermail/python-list/2001-October/109973.html)
+    # These constants should be present as long as poll is available
+
+    @unittest.skipUnless(hasattr(select, 'poll'), 'select.poll required')
+    def test_readwrite(self):
+        # Check that correct methods are called by readwrite()
+
+        attributes = ('read', 'expt', 'write', 'closed', 'error_handled')
+
+        expected = (
+            (select.POLLIN, 'read'),
+            (select.POLLPRI, 'expt'),
+            (select.POLLOUT, 'write'),
+            (select.POLLERR, 'closed'),
+            (select.POLLHUP, 'closed'),
+            (select.POLLNVAL, 'closed'),
+            )
+
+        class testobj:
+            def __init__(self):
+                self.read = False
+                self.write = False
+                self.closed = False
+                self.expt = False
+                self.error_handled = False
+
+            def handle_read_event(self):
+                self.read = True
+
+            def handle_write_event(self):
+                self.write = True
+
+            def handle_close(self):
+                self.closed = True
+
+            def handle_expt_event(self):
+                self.expt = True
+
+            def handle_error(self):
+                self.error_handled = True
+
+        for flag, expectedattr in expected:
+            tobj = testobj()
+            self.assertEqual(getattr(tobj, expectedattr), False)
+            asyncore.readwrite(tobj, flag)
+
+            # Only the attribute modified by the routine we expect to be
+            # called should be True.
+            for attr in attributes:
+                self.assertEqual(getattr(tobj, attr), attr==expectedattr)
+
+            # check that ExitNow exceptions in the object handler method
+            # bubbles all the way up through asyncore readwrite call
+            tr1 = exitingdummy()
+            self.assertRaises(asyncore.ExitNow, asyncore.readwrite, tr1, flag)
+
+            # check that an exception other than ExitNow in the object handler
+            # method causes the handle_error method to get called
+            tr2 = crashingdummy()
+            self.assertEqual(tr2.error_handled, False)
+            asyncore.readwrite(tr2, flag)
+            self.assertEqual(tr2.error_handled, True)
+
+    def test_closeall(self):
+        self.closeall_check(False)
+
+    def test_closeall_default(self):
+        self.closeall_check(True)
+
+    def closeall_check(self, usedefault):
+        # Check that close_all() closes everything in a given map
+
+        l = []
+        testmap = {}
+        for i in range(10):
+            c = dummychannel()
+            l.append(c)
+            self.assertEqual(c.socket.closed, False)
+            testmap[i] = c
+
+        if usedefault:
+            socketmap = asyncore.socket_map
+            try:
+                asyncore.socket_map = testmap
+                asyncore.close_all()
+            finally:
+                testmap, asyncore.socket_map = asyncore.socket_map, socketmap
+        else:
+            asyncore.close_all(testmap)
+
+        self.assertEqual(len(testmap), 0)
+
+        for c in l:
+            self.assertEqual(c.socket.closed, True)
+
+    def test_compact_traceback(self):
+        try:
+            raise Exception("I don't like spam!")
+        except:
+            real_t, real_v, real_tb = sys.exc_info()
+            r = asyncore.compact_traceback()
+        else:
+            self.fail("Expected exception")
+
+        (f, function, line), t, v, info = r
+        self.assertEqual(os.path.split(f)[-1], 'test_asyncore.py')
+        self.assertEqual(function, 'test_compact_traceback')
+        self.assertEqual(t, real_t)
+        self.assertEqual(v, real_v)
+        self.assertEqual(info, '[%s|%s|%s]' % (f, function, line))
+
+
+class DispatcherTests(unittest.TestCase):
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        asyncore.close_all()
+
+    def test_basic(self):
+        d = asyncore.dispatcher()
+        self.assertEqual(d.readable(), True)
+        self.assertEqual(d.writable(), True)
+
+    def test_repr(self):
+        d = asyncore.dispatcher()
+        self.assertEqual(repr(d), '<asyncore.dispatcher at %#x>' % id(d))
+
+    def test_log(self):
+        d = asyncore.dispatcher()
+
+        # capture output of dispatcher.log() (to stderr)
+        l1 = "Lovely spam! Wonderful spam!"
+        l2 = "I don't like spam!"
+        with support.captured_stderr() as stderr:
+            d.log(l1)
+            d.log(l2)
+
+        lines = stderr.getvalue().splitlines()
+        self.assertEqual(lines, ['log: %s' % l1, 'log: %s' % l2])
+
+    def test_log_info(self):
+        d = asyncore.dispatcher()
+
+        # capture output of dispatcher.log_info() (to stdout via print)
+        l1 = "Have you got anything without spam?"
+        l2 = "Why can't she have egg bacon spam and sausage?"
+        l3 = "THAT'S got spam in it!"
+        with support.captured_stdout() as stdout:
+            d.log_info(l1, 'EGGS')
+            d.log_info(l2)
+            d.log_info(l3, 'SPAM')
+
+        lines = stdout.getvalue().splitlines()
+        expected = ['EGGS: %s' % l1, 'info: %s' % l2, 'SPAM: %s' % l3]
+        self.assertEqual(lines, expected)
+
+    def test_unhandled(self):
+        d = asyncore.dispatcher()
+        d.ignore_log_types = ()
+
+        # capture output of dispatcher.log_info() (to stdout via print)
+        with support.captured_stdout() as stdout:
+            d.handle_expt()
+            d.handle_read()
+            d.handle_write()
+            d.handle_connect()
+
+        lines = stdout.getvalue().splitlines()
+        expected = ['warning: unhandled incoming priority event',
+                    'warning: unhandled read event',
+                    'warning: unhandled write event',
+                    'warning: unhandled connect event']
+        self.assertEqual(lines, expected)
+
+    def test_strerror(self):
+        # refers to bug #8573
+        err = asyncore._strerror(errno.EPERM)
+        if hasattr(os, 'strerror'):
+            self.assertEqual(err, os.strerror(errno.EPERM))
+        err = asyncore._strerror(-1)
+        self.assertTrue(err != "")
+
+
+class dispatcherwithsend_noread(asyncore.dispatcher_with_send):
+    def readable(self):
+        return False
+
+    def handle_connect(self):
+        pass
+
+
+class DispatcherWithSendTests(unittest.TestCase):
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        asyncore.close_all()
+
+    @threading_helper.reap_threads
+    def test_send(self):
+        evt = threading.Event()
+        sock = socket.socket()
+        sock.settimeout(3)
+        port = socket_helper.bind_port(sock)
+
+        cap = BytesIO()
+        args = (evt, cap, sock)
+        t = threading.Thread(target=capture_server, args=args)
+        t.start()
+        try:
+            # wait a little longer for the server to initialize (it sometimes
+            # refuses connections on slow machines without this wait)
+            time.sleep(0.2)
+
+            data = b"Suppose there isn't a 16-ton weight?"
+            d = dispatcherwithsend_noread()
+            d.create_socket()
+            d.connect((socket_helper.HOST, port))
+
+            # give time for socket to connect
+            time.sleep(0.1)
+
+            d.send(data)
+            d.send(data)
+            d.send(b'\n')
+
+            n = 1000
+            while d.out_buffer and n > 0:
+                asyncore.poll()
+                n -= 1
+
+            evt.wait()
+
+            self.assertEqual(cap.getvalue(), data*2)
+        finally:
+            threading_helper.join_thread(t)
+
+
+@unittest.skipUnless(hasattr(asyncore, 'file_wrapper'),
+                     'asyncore.file_wrapper required')
+class FileWrapperTest(unittest.TestCase):
+    def setUp(self):
+        self.d = b"It's not dead, it's sleeping!"
+        with open(os_helper.TESTFN, 'wb') as file:
+            file.write(self.d)
+
+    def tearDown(self):
+        os_helper.unlink(os_helper.TESTFN)
+
+    def test_recv(self):
+        fd = os.open(os_helper.TESTFN, os.O_RDONLY)
+        w = asyncore.file_wrapper(fd)
+        os.close(fd)
+
+        self.assertNotEqual(w.fd, fd)
+        self.assertNotEqual(w.fileno(), fd)
+        self.assertEqual(w.recv(13), b"It's not dead")
+        self.assertEqual(w.read(6), b", it's")
+        w.close()
+        self.assertRaises(OSError, w.read, 1)
+
+    def test_send(self):
+        d1 = b"Come again?"
+        d2 = b"I want to buy some cheese."
+        fd = os.open(os_helper.TESTFN, os.O_WRONLY | os.O_APPEND)
+        w = asyncore.file_wrapper(fd)
+        os.close(fd)
+
+        w.write(d1)
+        w.send(d2)
+        w.close()
+        with open(os_helper.TESTFN, 'rb') as file:
+            self.assertEqual(file.read(), self.d + d1 + d2)
+
+    @unittest.skipUnless(hasattr(asyncore, 'file_dispatcher'),
+                         'asyncore.file_dispatcher required')
+    def test_dispatcher(self):
+        fd = os.open(os_helper.TESTFN, os.O_RDONLY)
+        data = []
+        class FileDispatcher(asyncore.file_dispatcher):
+            def handle_read(self):
+                data.append(self.recv(29))
+        s = FileDispatcher(fd)
+        os.close(fd)
+        asyncore.loop(timeout=0.01, use_poll=True, count=2)
+        self.assertEqual(b"".join(data), self.d)
+
+    def test_resource_warning(self):
+        # Issue #11453
+        fd = os.open(os_helper.TESTFN, os.O_RDONLY)
+        f = asyncore.file_wrapper(fd)
+
+        os.close(fd)
+        with warnings_helper.check_warnings(('', ResourceWarning)):
+            f = None
+            support.gc_collect()
+
+    def test_close_twice(self):
+        fd = os.open(os_helper.TESTFN, os.O_RDONLY)
+        f = asyncore.file_wrapper(fd)
+        os.close(fd)
+
+        os.close(f.fd)  # file_wrapper dupped fd
+        with self.assertRaises(OSError):
+            f.close()
+
+        self.assertEqual(f.fd, -1)
+        # calling close twice should not fail
+        f.close()
+
+
+class BaseTestHandler(asyncore.dispatcher):
+
+    def __init__(self, sock=None):
+        asyncore.dispatcher.__init__(self, sock)
+        self.flag = False
+
+    def handle_accept(self):
+        raise Exception("handle_accept not supposed to be called")
+
+    def handle_accepted(self):
+        raise Exception("handle_accepted not supposed to be called")
+
+    def handle_connect(self):
+        raise Exception("handle_connect not supposed to be called")
+
+    def handle_expt(self):
+        raise Exception("handle_expt not supposed to be called")
+
+    def handle_close(self):
+        raise Exception("handle_close not supposed to be called")
+
+    def handle_error(self):
+        raise
+
+
+class BaseServer(asyncore.dispatcher):
+    """A server which listens on an address and dispatches the
+    connection to a handler.
+    """
+
+    def __init__(self, family, addr, handler=BaseTestHandler):
+        asyncore.dispatcher.__init__(self)
+        self.create_socket(family)
+        self.set_reuse_addr()
+        bind_af_aware(self.socket, addr)
+        self.listen(5)
+        self.handler = handler
+
+    @property
+    def address(self):
+        return self.socket.getsockname()
+
+    def handle_accepted(self, sock, addr):
+        self.handler(sock)
+
+    def handle_error(self):
+        raise
+
+
+class BaseClient(BaseTestHandler):
+
+    def __init__(self, family, address):
+        BaseTestHandler.__init__(self)
+        self.create_socket(family)
+        self.connect(address)
+
+    def handle_connect(self):
+        pass
+
+
+class BaseTestAPI:
+
+    def tearDown(self):
+        asyncore.close_all(ignore_all=True)
+
+    def loop_waiting_for_flag(self, instance, timeout=5):
+        timeout = float(timeout) / 100
+        count = 100
+        while asyncore.socket_map and count > 0:
+            asyncore.loop(timeout=0.01, count=1, use_poll=self.use_poll)
+            if instance.flag:
+                return
+            count -= 1
+            time.sleep(timeout)
+        self.fail("flag not set")
+
+    def test_handle_connect(self):
+        # make sure handle_connect is called on connect()
+
+        class TestClient(BaseClient):
+            def handle_connect(self):
+                self.flag = True
+
+        server = BaseServer(self.family, self.addr)
+        client = TestClient(self.family, server.address)
+        self.loop_waiting_for_flag(client)
+
+    def test_handle_accept(self):
+        # make sure handle_accept() is called when a client connects
+
+        class TestListener(BaseTestHandler):
+
+            def __init__(self, family, addr):
+                BaseTestHandler.__init__(self)
+                self.create_socket(family)
+                bind_af_aware(self.socket, addr)
+                self.listen(5)
+                self.address = self.socket.getsockname()
+
+            def handle_accept(self):
+                self.flag = True
+
+        server = TestListener(self.family, self.addr)
+        client = BaseClient(self.family, server.address)
+        self.loop_waiting_for_flag(server)
+
+    def test_handle_accepted(self):
+        # make sure handle_accepted() is called when a client connects
+
+        class TestListener(BaseTestHandler):
+
+            def __init__(self, family, addr):
+                BaseTestHandler.__init__(self)
+                self.create_socket(family)
+                bind_af_aware(self.socket, addr)
+                self.listen(5)
+                self.address = self.socket.getsockname()
+
+            def handle_accept(self):
+                asyncore.dispatcher.handle_accept(self)
+
+            def handle_accepted(self, sock, addr):
+                sock.close()
+                self.flag = True
+
+        server = TestListener(self.family, self.addr)
+        client = BaseClient(self.family, server.address)
+        self.loop_waiting_for_flag(server)
+
+
+    def test_handle_read(self):
+        # make sure handle_read is called on data received
+
+        class TestClient(BaseClient):
+            def handle_read(self):
+                self.flag = True
+
+        class TestHandler(BaseTestHandler):
+            def __init__(self, conn):
+                BaseTestHandler.__init__(self, conn)
+                self.send(b'x' * 1024)
+
+        server = BaseServer(self.family, self.addr, TestHandler)
+        client = TestClient(self.family, server.address)
+        self.loop_waiting_for_flag(client)
+
+    def test_handle_write(self):
+        # make sure handle_write is called
+
+        class TestClient(BaseClient):
+            def handle_write(self):
+                self.flag = True
+
+        server = BaseServer(self.family, self.addr)
+        client = TestClient(self.family, server.address)
+        self.loop_waiting_for_flag(client)
+
+    def test_handle_close(self):
+        # make sure handle_close is called when the other end closes
+        # the connection
+
+        class TestClient(BaseClient):
+
+            def handle_read(self):
+                # in order to make handle_close be called we are supposed
+                # to make at least one recv() call
+                self.recv(1024)
+
+            def handle_close(self):
+                self.flag = True
+                self.close()
+
+        class TestHandler(BaseTestHandler):
+            def __init__(self, conn):
+                BaseTestHandler.__init__(self, conn)
+                self.close()
+
+        server = BaseServer(self.family, self.addr, TestHandler)
+        client = TestClient(self.family, server.address)
+        self.loop_waiting_for_flag(client)
+
+    def test_handle_close_after_conn_broken(self):
+        # Check that ECONNRESET/EPIPE is correctly handled (issues #5661 and
+        # #11265).
+
+        data = b'\0' * 128
+
+        class TestClient(BaseClient):
+
+            def handle_write(self):
+                self.send(data)
+
+            def handle_close(self):
+                self.flag = True
+                self.close()
+
+            def handle_expt(self):
+                self.flag = True
+                self.close()
+
+        class TestHandler(BaseTestHandler):
+
+            def handle_read(self):
+                self.recv(len(data))
+                self.close()
+
+            def writable(self):
+                return False
+
+        server = BaseServer(self.family, self.addr, TestHandler)
+        client = TestClient(self.family, server.address)
+        self.loop_waiting_for_flag(client)
+
+    @unittest.skipIf(sys.platform.startswith("sunos"),
+                     "OOB support is broken on Solaris")
+    def test_handle_expt(self):
+        # Make sure handle_expt is called on OOB data received.
+        # Note: this might fail on some platforms as OOB data is
+        # tenuously supported and rarely used.
+        if HAS_UNIX_SOCKETS and self.family == socket.AF_UNIX:
+            self.skipTest("Not applicable to AF_UNIX sockets.")
+
+        if sys.platform == "darwin" and self.use_poll:
+            self.skipTest("poll may fail on macOS; see issue #28087")
+
+        class TestClient(BaseClient):
+            def handle_expt(self):
+                self.socket.recv(1024, socket.MSG_OOB)
+                self.flag = True
+
+        class TestHandler(BaseTestHandler):
+            def __init__(self, conn):
+                BaseTestHandler.__init__(self, conn)
+                self.socket.send(bytes(chr(244), 'latin-1'), socket.MSG_OOB)
+
+        server = BaseServer(self.family, self.addr, TestHandler)
+        client = TestClient(self.family, server.address)
+        self.loop_waiting_for_flag(client)
+
+    def test_handle_error(self):
+
+        class TestClient(BaseClient):
+            def handle_write(self):
+                1.0 / 0
+            def handle_error(self):
+                self.flag = True
+                try:
+                    raise
+                except ZeroDivisionError:
+                    pass
+                else:
+                    raise Exception("exception not raised")
+
+        server = BaseServer(self.family, self.addr)
+        client = TestClient(self.family, server.address)
+        self.loop_waiting_for_flag(client)
+
+    def test_connection_attributes(self):
+        server = BaseServer(self.family, self.addr)
+        client = BaseClient(self.family, server.address)
+
+        # we start disconnected
+        self.assertFalse(server.connected)
+        self.assertTrue(server.accepting)
+        # this can't be taken for granted across all platforms
+        #self.assertFalse(client.connected)
+        self.assertFalse(client.accepting)
+
+        # execute some loops so that client connects to server
+        asyncore.loop(timeout=0.01, use_poll=self.use_poll, count=100)
+        self.assertFalse(server.connected)
+        self.assertTrue(server.accepting)
+        self.assertTrue(client.connected)
+        self.assertFalse(client.accepting)
+
+        # disconnect the client
+        client.close()
+        self.assertFalse(server.connected)
+        self.assertTrue(server.accepting)
+        self.assertFalse(client.connected)
+        self.assertFalse(client.accepting)
+
+        # stop serving
+        server.close()
+        self.assertFalse(server.connected)
+        self.assertFalse(server.accepting)
+
+    def test_create_socket(self):
+        s = asyncore.dispatcher()
+        s.create_socket(self.family)
+        self.assertEqual(s.socket.type, socket.SOCK_STREAM)
+        self.assertEqual(s.socket.family, self.family)
+        self.assertEqual(s.socket.gettimeout(), 0)
+        self.assertFalse(s.socket.get_inheritable())
+
+    def test_bind(self):
+        if HAS_UNIX_SOCKETS and self.family == socket.AF_UNIX:
+            self.skipTest("Not applicable to AF_UNIX sockets.")
+        s1 = asyncore.dispatcher()
+        s1.create_socket(self.family)
+        s1.bind(self.addr)
+        s1.listen(5)
+        port = s1.socket.getsockname()[1]
+
+        s2 = asyncore.dispatcher()
+        s2.create_socket(self.family)
+        # EADDRINUSE indicates the socket was correctly bound
+        self.assertRaises(OSError, s2.bind, (self.addr[0], port))
+
+    def test_set_reuse_addr(self):
+        if HAS_UNIX_SOCKETS and self.family == socket.AF_UNIX:
+            self.skipTest("Not applicable to AF_UNIX sockets.")
+
+        with socket.socket(self.family) as sock:
+            try:
+                sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+            except OSError:
+                unittest.skip("SO_REUSEADDR not supported on this platform")
+            else:
+                # if SO_REUSEADDR succeeded for sock we expect asyncore
+                # to do the same
+                s = asyncore.dispatcher(socket.socket(self.family))
+                self.assertFalse(s.socket.getsockopt(socket.SOL_SOCKET,
+                                                     socket.SO_REUSEADDR))
+                s.socket.close()
+                s.create_socket(self.family)
+                s.set_reuse_addr()
+                self.assertTrue(s.socket.getsockopt(socket.SOL_SOCKET,
+                                                     socket.SO_REUSEADDR))
+
+    @threading_helper.reap_threads
+    def test_quick_connect(self):
+        # see: http://bugs.python.org/issue10340
+        if self.family not in (socket.AF_INET, getattr(socket, "AF_INET6", object())):
+            self.skipTest("test specific to AF_INET and AF_INET6")
+
+        server = BaseServer(self.family, self.addr)
+        # run the thread 500 ms: the socket should be connected in 200 ms
+        t = threading.Thread(target=lambda: asyncore.loop(timeout=0.1,
+                                                          count=5))
+        t.start()
+        try:
+            with socket.socket(self.family, socket.SOCK_STREAM) as s:
+                s.settimeout(.2)
+                s.setsockopt(socket.SOL_SOCKET, socket.SO_LINGER,
+                             struct.pack('ii', 1, 0))
+
+                try:
+                    s.connect(server.address)
+                except OSError:
+                    pass
+        finally:
+            threading_helper.join_thread(t)
+
+class TestAPI_UseIPv4Sockets(BaseTestAPI):
+    family = socket.AF_INET
+    addr = (socket_helper.HOST, 0)
+
+@unittest.skipUnless(socket_helper.IPV6_ENABLED, 'IPv6 support required')
+class TestAPI_UseIPv6Sockets(BaseTestAPI):
+    family = socket.AF_INET6
+    addr = (socket_helper.HOSTv6, 0)
+
+@unittest.skipUnless(HAS_UNIX_SOCKETS, 'Unix sockets required')
+class TestAPI_UseUnixSockets(BaseTestAPI):
+    if HAS_UNIX_SOCKETS:
+        family = socket.AF_UNIX
+    addr = os_helper.TESTFN
+
+    def tearDown(self):
+        os_helper.unlink(self.addr)
+        BaseTestAPI.tearDown(self)
+
+class TestAPI_UseIPv4Select(TestAPI_UseIPv4Sockets, unittest.TestCase):
+    use_poll = False
+
+@unittest.skipUnless(hasattr(select, 'poll'), 'select.poll required')
+class TestAPI_UseIPv4Poll(TestAPI_UseIPv4Sockets, unittest.TestCase):
+    use_poll = True
+
+class TestAPI_UseIPv6Select(TestAPI_UseIPv6Sockets, unittest.TestCase):
+    use_poll = False
+
+@unittest.skipUnless(hasattr(select, 'poll'), 'select.poll required')
+class TestAPI_UseIPv6Poll(TestAPI_UseIPv6Sockets, unittest.TestCase):
+    use_poll = True
+
+class TestAPI_UseUnixSocketsSelect(TestAPI_UseUnixSockets, unittest.TestCase):
+    use_poll = False
+
+@unittest.skipUnless(hasattr(select, 'poll'), 'select.poll required')
+class TestAPI_UseUnixSocketsPoll(TestAPI_UseUnixSockets, unittest.TestCase):
+    use_poll = True
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/Lib/test/test_ftplib.py b/Lib/test/test_ftplib.py
index c9edfac..56e3d8a 100644
--- a/Lib/test/test_ftplib.py
+++ b/Lib/test/test_ftplib.py
@@ -18,13 +18,17 @@ except ImportError:
 
 from unittest import TestCase, skipUnless
 from test import support
-from test.support import _asynchat as asynchat
-from test.support import _asyncore as asyncore
-from test.support import socket_helper
 from test.support import threading_helper
+from test.support import socket_helper
 from test.support import warnings_helper
 from test.support.socket_helper import HOST, HOSTv6
 
+import warnings
+with warnings.catch_warnings():
+    warnings.simplefilter('ignore', DeprecationWarning)
+    import asyncore
+    import asynchat
+
 
 TIMEOUT = support.LOOPBACK_TIMEOUT
 DEFAULT_ENCODING = 'utf-8'
diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
index e709ea3..85b6e5f 100644
--- a/Lib/test/test_logging.py
+++ b/Lib/test/test_logging.py
@@ -42,8 +42,6 @@ import sys
 import tempfile
 from test.support.script_helper import assert_python_ok, assert_python_failure
 from test import support
-from test.support import _asyncore as asyncore
-from test.support import _smtpd as smtpd
 from test.support import os_helper
 from test.support import socket_helper
 from test.support import threading_helper
@@ -61,6 +59,11 @@ from urllib.parse import urlparse, parse_qs
 from socketserver import (ThreadingUDPServer, DatagramRequestHandler,
                           ThreadingTCPServer, StreamRequestHandler)
 
+with warnings.catch_warnings():
+    warnings.simplefilter('ignore', DeprecationWarning)
+    import asyncore
+    import smtpd
+
 try:
     import win32evtlog, win32evtlogutil, pywintypes
 except ImportError:
diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 5e15340..8da0aa3 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -30,8 +30,6 @@ import unittest
 import uuid
 import warnings
 from test import support
-from test.support import _asynchat as asynchat
-from test.support import _asyncore as asyncore
 from test.support import import_helper
 from test.support import os_helper
 from test.support import socket_helper
@@ -39,6 +37,11 @@ from test.support import threading_helper
 from test.support import warnings_helper
 from platform import win32_is_iot
 
+with warnings.catch_warnings():
+    warnings.simplefilter('ignore', DeprecationWarning)
+    import asynchat
+    import asyncore
+
 try:
     import resource
 except ImportError:
diff --git a/Lib/test/test_poplib.py b/Lib/test/test_poplib.py
index 23c6be3..44cf523 100644
--- a/Lib/test/test_poplib.py
+++ b/Lib/test/test_poplib.py
@@ -12,12 +12,16 @@ import threading
 import unittest
 from unittest import TestCase, skipUnless
 from test import support as test_support
-from test.support import _asynchat as asynchat
-from test.support import _asyncore as asyncore
 from test.support import hashlib_helper
 from test.support import socket_helper
 from test.support import threading_helper
 
+import warnings
+with warnings.catch_warnings():
+    warnings.simplefilter('ignore', DeprecationWarning)
+    import asynchat
+    import asyncore
+
 HOST = socket_helper.HOST
 PORT = 0
 
diff --git a/Lib/test/test_smtpd.py b/Lib/test/test_smtpd.py
new file mode 100644
index 0000000..d2e150d
--- /dev/null
+++ b/Lib/test/test_smtpd.py
@@ -0,0 +1,1018 @@
+import unittest
+import textwrap
+from test import support, mock_socket
+from test.support import socket_helper
+from test.support import warnings_helper
+import socket
+import io
+
+import warnings
+with warnings.catch_warnings():
+    warnings.simplefilter('ignore', DeprecationWarning)
+    import smtpd
+    import asyncore
+
+
+class DummyServer(smtpd.SMTPServer):
+    def __init__(self, *args, **kwargs):
+        smtpd.SMTPServer.__init__(self, *args, **kwargs)
+        self.messages = []
+        if self._decode_data:
+            self.return_status = 'return status'
+        else:
+            self.return_status = b'return status'
+
+    def process_message(self, peer, mailfrom, rcpttos, data, **kw):
+        self.messages.append((peer, mailfrom, rcpttos, data))
+        if data == self.return_status:
+            return '250 Okish'
+        if 'mail_options' in kw and 'SMTPUTF8' in kw['mail_options']:
+            return '250 SMTPUTF8 message okish'
+
+
+class DummyDispatcherBroken(Exception):
+    pass
+
+
+class BrokenDummyServer(DummyServer):
+    def listen(self, num):
+        raise DummyDispatcherBroken()
+
+
+class SMTPDServerTest(unittest.TestCase):
+    def setUp(self):
+        smtpd.socket = asyncore.socket = mock_socket
+
+    def test_process_message_unimplemented(self):
+        server = smtpd.SMTPServer((socket_helper.HOST, 0), ('b', 0),
+                                  decode_data=True)
+        conn, addr = server.accept()
+        channel = smtpd.SMTPChannel(server, conn, addr, decode_data=True)
+
+        def write_line(line):
+            channel.socket.queue_recv(line)
+            channel.handle_read()
+
+        write_line(b'HELO example')
+        write_line(b'MAIL From:eggs@example')
+        write_line(b'RCPT To:spam@example')
+        write_line(b'DATA')
+        self.assertRaises(NotImplementedError, write_line, b'spam\r\n.\r\n')
+
+    def test_decode_data_and_enable_SMTPUTF8_raises(self):
+        self.assertRaises(
+            ValueError,
+            smtpd.SMTPServer,
+            (socket_helper.HOST, 0),
+            ('b', 0),
+            enable_SMTPUTF8=True,
+            decode_data=True)
+
+    def tearDown(self):
+        asyncore.close_all()
+        asyncore.socket = smtpd.socket = socket
+
+
+class DebuggingServerTest(unittest.TestCase):
+
+    def setUp(self):
+        smtpd.socket = asyncore.socket = mock_socket
+
+    def send_data(self, channel, data, enable_SMTPUTF8=False):
+        def write_line(line):
+            channel.socket.queue_recv(line)
+            channel.handle_read()
+        write_line(b'EHLO example')
+        if enable_SMTPUTF8:
+            write_line(b'MAIL From:eggs@example BODY=8BITMIME SMTPUTF8')
+        else:
+            write_line(b'MAIL From:eggs@example')
+        write_line(b'RCPT To:spam@example')
+        write_line(b'DATA')
+        write_line(data)
+        write_line(b'.')
+
+    def test_process_message_with_decode_data_true(self):
+        server = smtpd.DebuggingServer((socket_helper.HOST, 0), ('b', 0),
+                                       decode_data=True)
+        conn, addr = server.accept()
+        channel = smtpd.SMTPChannel(server, conn, addr, decode_data=True)
+        with support.captured_stdout() as s:
+            self.send_data(channel, b'From: test\n\nhello\n')
+        stdout = s.getvalue()
+        self.assertEqual(stdout, textwrap.dedent("""\
+             ---------- MESSAGE FOLLOWS ----------
+             From: test
+             X-Peer: peer-address
+
+             hello
+             ------------ END MESSAGE ------------
+             """))
+
+    def test_process_message_with_decode_data_false(self):
+        server = smtpd.DebuggingServer((socket_helper.HOST, 0), ('b', 0))
+        conn, addr = server.accept()
+        channel = smtpd.SMTPChannel(server, conn, addr)
+        with support.captured_stdout() as s:
+            self.send_data(channel, b'From: test\n\nh\xc3\xa9llo\xff\n')
+        stdout = s.getvalue()
+        self.assertEqual(stdout, textwrap.dedent("""\
+             ---------- MESSAGE FOLLOWS ----------
+             b'From: test'
+             b'X-Peer: peer-address'
+             b''
+             b'h\\xc3\\xa9llo\\xff'
+             ------------ END MESSAGE ------------
+             """))
+
+    def test_process_message_with_enable_SMTPUTF8_true(self):
+        server = smtpd.DebuggingServer((socket_helper.HOST, 0), ('b', 0),
+                                       enable_SMTPUTF8=True)
+        conn, addr = server.accept()
+        channel = smtpd.SMTPChannel(server, conn, addr, enable_SMTPUTF8=True)
+        with support.captured_stdout() as s:
+            self.send_data(channel, b'From: test\n\nh\xc3\xa9llo\xff\n')
+        stdout = s.getvalue()
+        self.assertEqual(stdout, textwrap.dedent("""\
+             ---------- MESSAGE FOLLOWS ----------
+             b'From: test'
+             b'X-Peer: peer-address'
+             b''
+             b'h\\xc3\\xa9llo\\xff'
+             ------------ END MESSAGE ------------
+             """))
+
+    def test_process_SMTPUTF8_message_with_enable_SMTPUTF8_true(self):
+        server = smtpd.DebuggingServer((socket_helper.HOST, 0), ('b', 0),
+                                       enable_SMTPUTF8=True)
+        conn, addr = server.accept()
+        channel = smtpd.SMTPChannel(server, conn, addr, enable_SMTPUTF8=True)
+        with support.captured_stdout() as s:
+            self.send_data(channel, b'From: test\n\nh\xc3\xa9llo\xff\n',
+                           enable_SMTPUTF8=True)
+        stdout = s.getvalue()
+        self.assertEqual(stdout, textwrap.dedent("""\
+             ---------- MESSAGE FOLLOWS ----------
+             mail options: ['BODY=8BITMIME', 'SMTPUTF8']
+             b'From: test'
+             b'X-Peer: peer-address'
+             b''
+             b'h\\xc3\\xa9llo\\xff'
+             ------------ END MESSAGE ------------
+             """))
+
+    def tearDown(self):
+        asyncore.close_all()
+        asyncore.socket = smtpd.socket = socket
+
+
+class TestFamilyDetection(unittest.TestCase):
+    def setUp(self):
+        smtpd.socket = asyncore.socket = mock_socket
+
+    def tearDown(self):
+        asyncore.close_all()
+        asyncore.socket = smtpd.socket = socket
+
+    @unittest.skipUnless(socket_helper.IPV6_ENABLED, "IPv6 not enabled")
+    def test_socket_uses_IPv6(self):
+        server = smtpd.SMTPServer((socket_helper.HOSTv6, 0), (socket_helper.HOSTv4, 0))
+        self.assertEqual(server.socket.family, socket.AF_INET6)
+
+    def test_socket_uses_IPv4(self):
+        server = smtpd.SMTPServer((socket_helper.HOSTv4, 0), (socket_helper.HOSTv6, 0))
+        self.assertEqual(server.socket.family, socket.AF_INET)
+
+
+class TestRcptOptionParsing(unittest.TestCase):
+    error_response = (b'555 RCPT TO parameters not recognized or not '
+                      b'implemented\r\n')
+
+    def setUp(self):
+        smtpd.socket = asyncore.socket = mock_socket
+        self.old_debugstream = smtpd.DEBUGSTREAM
+        self.debug = smtpd.DEBUGSTREAM = io.StringIO()
+
+    def tearDown(self):
+        asyncore.close_all()
+        asyncore.socket = smtpd.socket = socket
+        smtpd.DEBUGSTREAM = self.old_debugstream
+
+    def write_line(self, channel, line):
+        channel.socket.queue_recv(line)
+        channel.handle_read()
+
+    def test_params_rejected(self):
+        server = DummyServer((socket_helper.HOST, 0), ('b', 0))
+        conn, addr = server.accept()
+        channel = smtpd.SMTPChannel(server, conn, addr)
+        self.write_line(channel, b'EHLO example')
+        self.write_line(channel, b'MAIL from: <foo@example.com> size=20')
+        self.write_line(channel, b'RCPT to: <foo@example.com> foo=bar')
+        self.assertEqual(channel.socket.last, self.error_response)
+
+    def test_nothing_accepted(self):
+        server = DummyServer((socket_helper.HOST, 0), ('b', 0))
+        conn, addr = server.accept()
+        channel = smtpd.SMTPChannel(server, conn, addr)
+        self.write_line(channel, b'EHLO example')
+        self.write_line(channel, b'MAIL from: <foo@example.com> size=20')
+        self.write_line(channel, b'RCPT to: <foo@example.com>')
+        self.assertEqual(channel.socket.last, b'250 OK\r\n')
+
+
+class TestMailOptionParsing(unittest.TestCase):
+    error_response = (b'555 MAIL FROM parameters not recognized or not '
+                      b'implemented\r\n')
+
+    def setUp(self):
+        smtpd.socket = asyncore.socket = mock_socket
+        self.old_debugstream = smtpd.DEBUGSTREAM
+        self.debug = smtpd.DEBUGSTREAM = io.StringIO()
+
+    def tearDown(self):
+        asyncore.close_all()
+        asyncore.socket = smtpd.socket = socket
+        smtpd.DEBUGSTREAM = self.old_debugstream
+
+    def write_line(self, channel, line):
+        channel.socket.queue_recv(line)
+        channel.handle_read()
+
+    def test_with_decode_data_true(self):
+        server = DummyServer((socket_helper.HOST, 0), ('b', 0), decode_data=True)
+        conn, addr = server.accept()
+        channel = smtpd.SMTPChannel(server, conn, addr, decode_data=True)
+        self.write_line(channel, b'EHLO example')
+        for line in [
+            b'MAIL from: <foo@example.com> size=20 SMTPUTF8',
+            b'MAIL from: <foo@example.com> size=20 SMTPUTF8 BODY=8BITMIME',
+            b'MAIL from: <foo@example.com> size=20 BODY=UNKNOWN',
+            b'MAIL from: <foo@example.com> size=20 body=8bitmime',
+        ]:
+            self.write_line(channel, line)
+            self.assertEqual(channel.socket.last, self.error_response)
+        self.write_line(channel, b'MAIL from: <foo@example.com> size=20')
+        self.assertEqual(channel.socket.last, b'250 OK\r\n')
+
+    def test_with_decode_data_false(self):
+        server = DummyServer((socket_helper.HOST, 0), ('b', 0))
+        conn, addr = server.accept()
+        channel = smtpd.SMTPChannel(server, conn, addr)
+        self.write_line(channel, b'EHLO example')
+        for line in [
+            b'MAIL from: <foo@example.com> size=20 SMTPUTF8',
+            b'MAIL from: <foo@example.com> size=20 SMTPUTF8 BODY=8BITMIME',
+        ]:
+            self.write_line(channel, line)
+            self.assertEqual(channel.socket.last, self.error_response)
+        self.write_line(
+            channel,
+            b'MAIL from: <foo@example.com> size=20 SMTPUTF8 BODY=UNKNOWN')
+        self.assertEqual(
+            channel.socket.last,
+            b'501 Error: BODY can only be one of 7BIT, 8BITMIME\r\n')
+        self.write_line(
+            channel, b'MAIL from: <foo@example.com> size=20 body=8bitmime')
+        self.assertEqual(channel.socket.last, b'250 OK\r\n')
+
+    def test_with_enable_smtputf8_true(self):
+        server = DummyServer((socket_helper.HOST, 0), ('b', 0), enable_SMTPUTF8=True)
+        conn, addr = server.accept()
+        channel = smtpd.SMTPChannel(server, conn, addr, enable_SMTPUTF8=True)
+        self.write_line(channel, b'EHLO example')
+        self.write_line(
+            channel,
+            b'MAIL from: <foo@example.com> size=20 body=8bitmime smtputf8')
+        self.assertEqual(channel.socket.last, b'250 OK\r\n')
+
+
+class SMTPDChannelTest(unittest.TestCase):
+    def setUp(self):
+        smtpd.socket = asyncore.socket = mock_socket
+        self.old_debugstream = smtpd.DEBUGSTREAM
+        self.debug = smtpd.DEBUGSTREAM = io.StringIO()
+        self.server = DummyServer((socket_helper.HOST, 0), ('b', 0),
+                                  decode_data=True)
+        conn, addr = self.server.accept()
+        self.channel = smtpd.SMTPChannel(self.server, conn, addr,
+                                         decode_data=True)
+
+    def tearDown(self):
+        asyncore.close_all()
+        asyncore.socket = smtpd.socket = socket
+        smtpd.DEBUGSTREAM = self.old_debugstream
+
+    def write_line(self, line):
+        self.channel.socket.queue_recv(line)
+        self.channel.handle_read()
+
+    def test_broken_connect(self):
+        self.assertRaises(
+            DummyDispatcherBroken, BrokenDummyServer,
+            (socket_helper.HOST, 0), ('b', 0), decode_data=True)
+
+    def test_decode_data_and_enable_SMTPUTF8_raises(self):
+        self.assertRaises(
+            ValueError, smtpd.SMTPChannel,
+            self.server, self.channel.conn, self.channel.addr,
+            enable_SMTPUTF8=True, decode_data=True)
+
+    def test_server_accept(self):
+        self.server.handle_accept()
+
+    def test_missing_data(self):
+        self.write_line(b'')
+        self.assertEqual(self.channel.socket.last,
+                         b'500 Error: bad syntax\r\n')
+
+    def test_EHLO(self):
+        self.write_line(b'EHLO example')
+        self.assertEqual(self.channel.socket.last, b'250 HELP\r\n')
+
+    def test_EHLO_bad_syntax(self):
+        self.write_line(b'EHLO')
+        self.assertEqual(self.channel.socket.last,
+                         b'501 Syntax: EHLO hostname\r\n')
+
+    def test_EHLO_duplicate(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'EHLO example')
+        self.assertEqual(self.channel.socket.last,
+                         b'503 Duplicate HELO/EHLO\r\n')
+
+    def test_EHLO_HELO_duplicate(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'HELO example')
+        self.assertEqual(self.channel.socket.last,
+                         b'503 Duplicate HELO/EHLO\r\n')
+
+    def test_HELO(self):
+        name = smtpd.socket.getfqdn()
+        self.write_line(b'HELO example')
+        self.assertEqual(self.channel.socket.last,
+                         '250 {}\r\n'.format(name).encode('ascii'))
+
+    def test_HELO_EHLO_duplicate(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'EHLO example')
+        self.assertEqual(self.channel.socket.last,
+                         b'503 Duplicate HELO/EHLO\r\n')
+
+    def test_HELP(self):
+        self.write_line(b'HELP')
+        self.assertEqual(self.channel.socket.last,
+                         b'250 Supported commands: EHLO HELO MAIL RCPT ' + \
+                         b'DATA RSET NOOP QUIT VRFY\r\n')
+
+    def test_HELP_command(self):
+        self.write_line(b'HELP MAIL')
+        self.assertEqual(self.channel.socket.last,
+                         b'250 Syntax: MAIL FROM: <address>\r\n')
+
+    def test_HELP_command_unknown(self):
+        self.write_line(b'HELP SPAM')
+        self.assertEqual(self.channel.socket.last,
+                         b'501 Supported commands: EHLO HELO MAIL RCPT ' + \
+                         b'DATA RSET NOOP QUIT VRFY\r\n')
+
+    def test_HELO_bad_syntax(self):
+        self.write_line(b'HELO')
+        self.assertEqual(self.channel.socket.last,
+                         b'501 Syntax: HELO hostname\r\n')
+
+    def test_HELO_duplicate(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'HELO example')
+        self.assertEqual(self.channel.socket.last,
+                         b'503 Duplicate HELO/EHLO\r\n')
+
+    def test_HELO_parameter_rejected_when_extensions_not_enabled(self):
+        self.extended_smtp = False
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL from:<foo@example.com> SIZE=1234')
+        self.assertEqual(self.channel.socket.last,
+                         b'501 Syntax: MAIL FROM: <address>\r\n')
+
+    def test_MAIL_allows_space_after_colon(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL from:   <foo@example.com>')
+        self.assertEqual(self.channel.socket.last,
+                         b'250 OK\r\n')
+
+    def test_extended_MAIL_allows_space_after_colon(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL from:   <foo@example.com> size=20')
+        self.assertEqual(self.channel.socket.last,
+                         b'250 OK\r\n')
+
+    def test_NOOP(self):
+        self.write_line(b'NOOP')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+    def test_HELO_NOOP(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'NOOP')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+    def test_NOOP_bad_syntax(self):
+        self.write_line(b'NOOP hi')
+        self.assertEqual(self.channel.socket.last,
+                         b'501 Syntax: NOOP\r\n')
+
+    def test_QUIT(self):
+        self.write_line(b'QUIT')
+        self.assertEqual(self.channel.socket.last, b'221 Bye\r\n')
+
+    def test_HELO_QUIT(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'QUIT')
+        self.assertEqual(self.channel.socket.last, b'221 Bye\r\n')
+
+    def test_QUIT_arg_ignored(self):
+        self.write_line(b'QUIT bye bye')
+        self.assertEqual(self.channel.socket.last, b'221 Bye\r\n')
+
+    def test_bad_state(self):
+        self.channel.smtp_state = 'BAD STATE'
+        self.write_line(b'HELO example')
+        self.assertEqual(self.channel.socket.last,
+                         b'451 Internal confusion\r\n')
+
+    def test_command_too_long(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL from: ' +
+                        b'a' * self.channel.command_size_limit +
+                        b'@example')
+        self.assertEqual(self.channel.socket.last,
+                         b'500 Error: line too long\r\n')
+
+    def test_MAIL_command_limit_extended_with_SIZE(self):
+        self.write_line(b'EHLO example')
+        fill_len = self.channel.command_size_limit - len('MAIL from:<@example>')
+        self.write_line(b'MAIL from:<' +
+                        b'a' * fill_len +
+                        b'@example> SIZE=1234')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+        self.write_line(b'MAIL from:<' +
+                        b'a' * (fill_len + 26) +
+                        b'@example> SIZE=1234')
+        self.assertEqual(self.channel.socket.last,
+                         b'500 Error: line too long\r\n')
+
+    def test_MAIL_command_rejects_SMTPUTF8_by_default(self):
+        self.write_line(b'EHLO example')
+        self.write_line(
+            b'MAIL from: <naive@example.com> BODY=8BITMIME SMTPUTF8')
+        self.assertEqual(self.channel.socket.last[0:1], b'5')
+
+    def test_data_longer_than_default_data_size_limit(self):
+        # Hack the default so we don't have to generate so much data.
+        self.channel.data_size_limit = 1048
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.write_line(b'RCPT To:spam@example')
+        self.write_line(b'DATA')
+        self.write_line(b'A' * self.channel.data_size_limit +
+                        b'A\r\n.')
+        self.assertEqual(self.channel.socket.last,
+                         b'552 Error: Too much mail data\r\n')
+
+    def test_MAIL_size_parameter(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL FROM:<eggs@example> SIZE=512')
+        self.assertEqual(self.channel.socket.last,
+                         b'250 OK\r\n')
+
+    def test_MAIL_invalid_size_parameter(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL FROM:<eggs@example> SIZE=invalid')
+        self.assertEqual(self.channel.socket.last,
+            b'501 Syntax: MAIL FROM: <address> [SP <mail-parameters>]\r\n')
+
+    def test_MAIL_RCPT_unknown_parameters(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL FROM:<eggs@example> ham=green')
+        self.assertEqual(self.channel.socket.last,
+            b'555 MAIL FROM parameters not recognized or not implemented\r\n')
+
+        self.write_line(b'MAIL FROM:<eggs@example>')
+        self.write_line(b'RCPT TO:<eggs@example> ham=green')
+        self.assertEqual(self.channel.socket.last,
+            b'555 RCPT TO parameters not recognized or not implemented\r\n')
+
+    def test_MAIL_size_parameter_larger_than_default_data_size_limit(self):
+        self.channel.data_size_limit = 1048
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL FROM:<eggs@example> SIZE=2096')
+        self.assertEqual(self.channel.socket.last,
+            b'552 Error: message size exceeds fixed maximum message size\r\n')
+
+    def test_need_MAIL(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'RCPT to:spam@example')
+        self.assertEqual(self.channel.socket.last,
+            b'503 Error: need MAIL command\r\n')
+
+    def test_MAIL_syntax_HELO(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL from eggs@example')
+        self.assertEqual(self.channel.socket.last,
+            b'501 Syntax: MAIL FROM: <address>\r\n')
+
+    def test_MAIL_syntax_EHLO(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL from eggs@example')
+        self.assertEqual(self.channel.socket.last,
+            b'501 Syntax: MAIL FROM: <address> [SP <mail-parameters>]\r\n')
+
+    def test_MAIL_missing_address(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL from:')
+        self.assertEqual(self.channel.socket.last,
+            b'501 Syntax: MAIL FROM: <address>\r\n')
+
+    def test_MAIL_chevrons(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL from:<eggs@example>')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+    def test_MAIL_empty_chevrons(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL from:<>')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+    def test_MAIL_quoted_localpart(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL from: <"Fred Blogs"@example.com>')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.assertEqual(self.channel.mailfrom, '"Fred Blogs"@example.com')
+
+    def test_MAIL_quoted_localpart_no_angles(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL from: "Fred Blogs"@example.com')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.assertEqual(self.channel.mailfrom, '"Fred Blogs"@example.com')
+
+    def test_MAIL_quoted_localpart_with_size(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL from: <"Fred Blogs"@example.com> SIZE=1000')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.assertEqual(self.channel.mailfrom, '"Fred Blogs"@example.com')
+
+    def test_MAIL_quoted_localpart_with_size_no_angles(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL from: "Fred Blogs"@example.com SIZE=1000')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.assertEqual(self.channel.mailfrom, '"Fred Blogs"@example.com')
+
+    def test_nested_MAIL(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL from:eggs@example')
+        self.write_line(b'MAIL from:spam@example')
+        self.assertEqual(self.channel.socket.last,
+            b'503 Error: nested MAIL command\r\n')
+
+    def test_VRFY(self):
+        self.write_line(b'VRFY eggs@example')
+        self.assertEqual(self.channel.socket.last,
+            b'252 Cannot VRFY user, but will accept message and attempt ' + \
+            b'delivery\r\n')
+
+    def test_VRFY_syntax(self):
+        self.write_line(b'VRFY')
+        self.assertEqual(self.channel.socket.last,
+            b'501 Syntax: VRFY <address>\r\n')
+
+    def test_EXPN_not_implemented(self):
+        self.write_line(b'EXPN')
+        self.assertEqual(self.channel.socket.last,
+            b'502 EXPN not implemented\r\n')
+
+    def test_no_HELO_MAIL(self):
+        self.write_line(b'MAIL from:<foo@example.com>')
+        self.assertEqual(self.channel.socket.last,
+                         b'503 Error: send HELO first\r\n')
+
+    def test_need_RCPT(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.write_line(b'DATA')
+        self.assertEqual(self.channel.socket.last,
+            b'503 Error: need RCPT command\r\n')
+
+    def test_RCPT_syntax_HELO(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From: eggs@example')
+        self.write_line(b'RCPT to eggs@example')
+        self.assertEqual(self.channel.socket.last,
+            b'501 Syntax: RCPT TO: <address>\r\n')
+
+    def test_RCPT_syntax_EHLO(self):
+        self.write_line(b'EHLO example')
+        self.write_line(b'MAIL From: eggs@example')
+        self.write_line(b'RCPT to eggs@example')
+        self.assertEqual(self.channel.socket.last,
+            b'501 Syntax: RCPT TO: <address> [SP <mail-parameters>]\r\n')
+
+    def test_RCPT_lowercase_to_OK(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From: eggs@example')
+        self.write_line(b'RCPT to: <eggs@example>')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+    def test_no_HELO_RCPT(self):
+        self.write_line(b'RCPT to eggs@example')
+        self.assertEqual(self.channel.socket.last,
+                         b'503 Error: send HELO first\r\n')
+
+    def test_data_dialog(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.write_line(b'RCPT To:spam@example')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+        self.write_line(b'DATA')
+        self.assertEqual(self.channel.socket.last,
+            b'354 End data with <CR><LF>.<CR><LF>\r\n')
+        self.write_line(b'data\r\nmore\r\n.')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.assertEqual(self.server.messages,
+            [(('peer-address', 'peer-port'),
+              'eggs@example',
+              ['spam@example'],
+              'data\nmore')])
+
+    def test_DATA_syntax(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.write_line(b'RCPT To:spam@example')
+        self.write_line(b'DATA spam')
+        self.assertEqual(self.channel.socket.last, b'501 Syntax: DATA\r\n')
+
+    def test_no_HELO_DATA(self):
+        self.write_line(b'DATA spam')
+        self.assertEqual(self.channel.socket.last,
+                         b'503 Error: send HELO first\r\n')
+
+    def test_data_transparency_section_4_5_2(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.write_line(b'RCPT To:spam@example')
+        self.write_line(b'DATA')
+        self.write_line(b'..\r\n.\r\n')
+        self.assertEqual(self.channel.received_data, '.')
+
+    def test_multiple_RCPT(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.write_line(b'RCPT To:spam@example')
+        self.write_line(b'RCPT To:ham@example')
+        self.write_line(b'DATA')
+        self.write_line(b'data\r\n.')
+        self.assertEqual(self.server.messages,
+            [(('peer-address', 'peer-port'),
+              'eggs@example',
+              ['spam@example','ham@example'],
+              'data')])
+
+    def test_manual_status(self):
+        # checks that the Channel is able to return a custom status message
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.write_line(b'RCPT To:spam@example')
+        self.write_line(b'DATA')
+        self.write_line(b'return status\r\n.')
+        self.assertEqual(self.channel.socket.last, b'250 Okish\r\n')
+
+    def test_RSET(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.write_line(b'RCPT To:spam@example')
+        self.write_line(b'RSET')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.write_line(b'MAIL From:foo@example')
+        self.write_line(b'RCPT To:eggs@example')
+        self.write_line(b'DATA')
+        self.write_line(b'data\r\n.')
+        self.assertEqual(self.server.messages,
+            [(('peer-address', 'peer-port'),
+               'foo@example',
+               ['eggs@example'],
+               'data')])
+
+    def test_HELO_RSET(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'RSET')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+    def test_RSET_syntax(self):
+        self.write_line(b'RSET hi')
+        self.assertEqual(self.channel.socket.last, b'501 Syntax: RSET\r\n')
+
+    def test_unknown_command(self):
+        self.write_line(b'UNKNOWN_CMD')
+        self.assertEqual(self.channel.socket.last,
+                         b'500 Error: command "UNKNOWN_CMD" not ' + \
+                         b'recognized\r\n')
+
+    def test_attribute_deprecations(self):
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            spam = self.channel._SMTPChannel__server
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            self.channel._SMTPChannel__server = 'spam'
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            spam = self.channel._SMTPChannel__line
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            self.channel._SMTPChannel__line = 'spam'
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            spam = self.channel._SMTPChannel__state
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            self.channel._SMTPChannel__state = 'spam'
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            spam = self.channel._SMTPChannel__greeting
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            self.channel._SMTPChannel__greeting = 'spam'
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            spam = self.channel._SMTPChannel__mailfrom
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            self.channel._SMTPChannel__mailfrom = 'spam'
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            spam = self.channel._SMTPChannel__rcpttos
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            self.channel._SMTPChannel__rcpttos = 'spam'
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            spam = self.channel._SMTPChannel__data
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            self.channel._SMTPChannel__data = 'spam'
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            spam = self.channel._SMTPChannel__fqdn
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            self.channel._SMTPChannel__fqdn = 'spam'
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            spam = self.channel._SMTPChannel__peer
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            self.channel._SMTPChannel__peer = 'spam'
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            spam = self.channel._SMTPChannel__conn
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            self.channel._SMTPChannel__conn = 'spam'
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            spam = self.channel._SMTPChannel__addr
+        with warnings_helper.check_warnings(('', DeprecationWarning)):
+            self.channel._SMTPChannel__addr = 'spam'
+
+@unittest.skipUnless(socket_helper.IPV6_ENABLED, "IPv6 not enabled")
+class SMTPDChannelIPv6Test(SMTPDChannelTest):
+    def setUp(self):
+        smtpd.socket = asyncore.socket = mock_socket
+        self.old_debugstream = smtpd.DEBUGSTREAM
+        self.debug = smtpd.DEBUGSTREAM = io.StringIO()
+        self.server = DummyServer((socket_helper.HOSTv6, 0), ('b', 0),
+                                  decode_data=True)
+        conn, addr = self.server.accept()
+        self.channel = smtpd.SMTPChannel(self.server, conn, addr,
+                                         decode_data=True)
+
+class SMTPDChannelWithDataSizeLimitTest(unittest.TestCase):
+
+    def setUp(self):
+        smtpd.socket = asyncore.socket = mock_socket
+        self.old_debugstream = smtpd.DEBUGSTREAM
+        self.debug = smtpd.DEBUGSTREAM = io.StringIO()
+        self.server = DummyServer((socket_helper.HOST, 0), ('b', 0),
+                                  decode_data=True)
+        conn, addr = self.server.accept()
+        # Set DATA size limit to 32 bytes for easy testing
+        self.channel = smtpd.SMTPChannel(self.server, conn, addr, 32,
+                                         decode_data=True)
+
+    def tearDown(self):
+        asyncore.close_all()
+        asyncore.socket = smtpd.socket = socket
+        smtpd.DEBUGSTREAM = self.old_debugstream
+
+    def write_line(self, line):
+        self.channel.socket.queue_recv(line)
+        self.channel.handle_read()
+
+    def test_data_limit_dialog(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.write_line(b'RCPT To:spam@example')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+        self.write_line(b'DATA')
+        self.assertEqual(self.channel.socket.last,
+            b'354 End data with <CR><LF>.<CR><LF>\r\n')
+        self.write_line(b'data\r\nmore\r\n.')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.assertEqual(self.server.messages,
+            [(('peer-address', 'peer-port'),
+              'eggs@example',
+              ['spam@example'],
+              'data\nmore')])
+
+    def test_data_limit_dialog_too_much_data(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+        self.write_line(b'RCPT To:spam@example')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+        self.write_line(b'DATA')
+        self.assertEqual(self.channel.socket.last,
+            b'354 End data with <CR><LF>.<CR><LF>\r\n')
+        self.write_line(b'This message is longer than 32 bytes\r\n.')
+        self.assertEqual(self.channel.socket.last,
+                         b'552 Error: Too much mail data\r\n')
+
+
+class SMTPDChannelWithDecodeDataFalse(unittest.TestCase):
+
+    def setUp(self):
+        smtpd.socket = asyncore.socket = mock_socket
+        self.old_debugstream = smtpd.DEBUGSTREAM
+        self.debug = smtpd.DEBUGSTREAM = io.StringIO()
+        self.server = DummyServer((socket_helper.HOST, 0), ('b', 0))
+        conn, addr = self.server.accept()
+        self.channel = smtpd.SMTPChannel(self.server, conn, addr)
+
+    def tearDown(self):
+        asyncore.close_all()
+        asyncore.socket = smtpd.socket = socket
+        smtpd.DEBUGSTREAM = self.old_debugstream
+
+    def write_line(self, line):
+        self.channel.socket.queue_recv(line)
+        self.channel.handle_read()
+
+    def test_ascii_data(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.write_line(b'RCPT To:spam@example')
+        self.write_line(b'DATA')
+        self.write_line(b'plain ascii text')
+        self.write_line(b'.')
+        self.assertEqual(self.channel.received_data, b'plain ascii text')
+
+    def test_utf8_data(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.write_line(b'RCPT To:spam@example')
+        self.write_line(b'DATA')
+        self.write_line(b'utf8 enriched text: \xc5\xbc\xc5\xba\xc4\x87')
+        self.write_line(b'and some plain ascii')
+        self.write_line(b'.')
+        self.assertEqual(
+            self.channel.received_data,
+            b'utf8 enriched text: \xc5\xbc\xc5\xba\xc4\x87\n'
+                b'and some plain ascii')
+
+
+class SMTPDChannelWithDecodeDataTrue(unittest.TestCase):
+
+    def setUp(self):
+        smtpd.socket = asyncore.socket = mock_socket
+        self.old_debugstream = smtpd.DEBUGSTREAM
+        self.debug = smtpd.DEBUGSTREAM = io.StringIO()
+        self.server = DummyServer((socket_helper.HOST, 0), ('b', 0),
+                                  decode_data=True)
+        conn, addr = self.server.accept()
+        # Set decode_data to True
+        self.channel = smtpd.SMTPChannel(self.server, conn, addr,
+                decode_data=True)
+
+    def tearDown(self):
+        asyncore.close_all()
+        asyncore.socket = smtpd.socket = socket
+        smtpd.DEBUGSTREAM = self.old_debugstream
+
+    def write_line(self, line):
+        self.channel.socket.queue_recv(line)
+        self.channel.handle_read()
+
+    def test_ascii_data(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.write_line(b'RCPT To:spam@example')
+        self.write_line(b'DATA')
+        self.write_line(b'plain ascii text')
+        self.write_line(b'.')
+        self.assertEqual(self.channel.received_data, 'plain ascii text')
+
+    def test_utf8_data(self):
+        self.write_line(b'HELO example')
+        self.write_line(b'MAIL From:eggs@example')
+        self.write_line(b'RCPT To:spam@example')
+        self.write_line(b'DATA')
+        self.write_line(b'utf8 enriched text: \xc5\xbc\xc5\xba\xc4\x87')
+        self.write_line(b'and some plain ascii')
+        self.write_line(b'.')
+        self.assertEqual(
+            self.channel.received_data,
+            'utf8 enriched text: żźć\nand some plain ascii')
+
+
+class SMTPDChannelTestWithEnableSMTPUTF8True(unittest.TestCase):
+    def setUp(self):
+        smtpd.socket = asyncore.socket = mock_socket
+        self.old_debugstream = smtpd.DEBUGSTREAM
+        self.debug = smtpd.DEBUGSTREAM = io.StringIO()
+        self.server = DummyServer((socket_helper.HOST, 0), ('b', 0),
+                                  enable_SMTPUTF8=True)
+        conn, addr = self.server.accept()
+        self.channel = smtpd.SMTPChannel(self.server, conn, addr,
+                                         enable_SMTPUTF8=True)
+
+    def tearDown(self):
+        asyncore.close_all()
+        asyncore.socket = smtpd.socket = socket
+        smtpd.DEBUGSTREAM = self.old_debugstream
+
+    def write_line(self, line):
+        self.channel.socket.queue_recv(line)
+        self.channel.handle_read()
+
+    def test_MAIL_command_accepts_SMTPUTF8_when_announced(self):
+        self.write_line(b'EHLO example')
+        self.write_line(
+            'MAIL from: <naïve@example.com> BODY=8BITMIME SMTPUTF8'.encode(
+                'utf-8')
+        )
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+    def test_process_smtputf8_message(self):
+        self.write_line(b'EHLO example')
+        for mail_parameters in [b'', b'BODY=8BITMIME SMTPUTF8']:
+            self.write_line(b'MAIL from: <a@example> ' + mail_parameters)
+            self.assertEqual(self.channel.socket.last[0:3], b'250')
+            self.write_line(b'rcpt to:<b@example.com>')
+            self.assertEqual(self.channel.socket.last[0:3], b'250')
+            self.write_line(b'data')
+            self.assertEqual(self.channel.socket.last[0:3], b'354')
+            self.write_line(b'c\r\n.')
+            if mail_parameters == b'':
+                self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+            else:
+                self.assertEqual(self.channel.socket.last,
+                                 b'250 SMTPUTF8 message okish\r\n')
+
+    def test_utf8_data(self):
+        self.write_line(b'EHLO example')
+        self.write_line(
+            'MAIL From: naïve@examplé BODY=8BITMIME SMTPUTF8'.encode('utf-8'))
+        self.assertEqual(self.channel.socket.last[0:3], b'250')
+        self.write_line('RCPT To:späm@examplé'.encode('utf-8'))
+        self.assertEqual(self.channel.socket.last[0:3], b'250')
+        self.write_line(b'DATA')
+        self.assertEqual(self.channel.socket.last[0:3], b'354')
+        self.write_line(b'utf8 enriched text: \xc5\xbc\xc5\xba\xc4\x87')
+        self.write_line(b'.')
+        self.assertEqual(
+            self.channel.received_data,
+            b'utf8 enriched text: \xc5\xbc\xc5\xba\xc4\x87')
+
+    def test_MAIL_command_limit_extended_with_SIZE_and_SMTPUTF8(self):
+        self.write_line(b'ehlo example')
+        fill_len = (512 + 26 + 10) - len('mail from:<@example>')
+        self.write_line(b'MAIL from:<' +
+                        b'a' * (fill_len + 1) +
+                        b'@example>')
+        self.assertEqual(self.channel.socket.last,
+                         b'500 Error: line too long\r\n')
+        self.write_line(b'MAIL from:<' +
+                        b'a' * fill_len +
+                        b'@example>')
+        self.assertEqual(self.channel.socket.last, b'250 OK\r\n')
+
+    def test_multiple_emails_with_extended_command_length(self):
+        self.write_line(b'ehlo example')
+        fill_len = (512 + 26 + 10) - len('mail from:<@example>')
+        for char in [b'a', b'b', b'c']:
+            self.write_line(b'MAIL from:<' + char * fill_len + b'a@example>')
+            self.assertEqual(self.channel.socket.last[0:3], b'500')
+            self.write_line(b'MAIL from:<' + char * fill_len + b'@example>')
+            self.assertEqual(self.channel.socket.last[0:3], b'250')
+            self.write_line(b'rcpt to:<hans@example.com>')
+            self.assertEqual(self.channel.socket.last[0:3], b'250')
+            self.write_line(b'data')
+            self.assertEqual(self.channel.socket.last[0:3], b'354')
+            self.write_line(b'test\r\n.')
+            self.assertEqual(self.channel.socket.last[0:3], b'250')
+
+
+class MiscTestCase(unittest.TestCase):
+    def test__all__(self):
+        not_exported = {
+            "program", "Devnull", "DEBUGSTREAM", "NEWLINE", "COMMASPACE",
+            "DATA_SIZE_DEFAULT", "usage", "Options", "parseargs",
+        }
+        support.check__all__(self, smtpd, not_exported=not_exported)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/Lib/test/test_smtplib.py b/Lib/test/test_smtplib.py
index bdce3e3..9761a37 100644
--- a/Lib/test/test_smtplib.py
+++ b/Lib/test/test_smtplib.py
@@ -18,13 +18,17 @@ import threading
 
 import unittest
 from test import support, mock_socket
-from test.support import _asyncore as asyncore
-from test.support import _smtpd as smtpd
 from test.support import hashlib_helper
 from test.support import socket_helper
 from test.support import threading_helper
 from unittest.mock import Mock
 
+import warnings
+with warnings.catch_warnings():
+    warnings.simplefilter('ignore', DeprecationWarning)
+    import asyncore
+    import smtpd
+
 HOST = socket_helper.HOST
 
 if sys.platform == 'darwin':
diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py
index 88eeb07..981e2fe 100644
--- a/Lib/test/test_ssl.py
+++ b/Lib/test/test_ssl.py
@@ -4,7 +4,6 @@ import sys
 import unittest
 import unittest.mock
 from test import support
-from test.support import _asyncore as asyncore
 from test.support import import_helper
 from test.support import os_helper
 from test.support import socket_helper
@@ -31,6 +30,10 @@ try:
 except ImportError:
     ctypes = None
 
+import warnings
+with warnings.catch_warnings():
+    warnings.simplefilter('ignore', DeprecationWarning)
+    import asyncore
 
 ssl = import_helper.import_module("ssl")
 import _ssl
diff --git a/Misc/NEWS.d/next/Library/2021-11-11-12-59-10.bpo-28533.68mMZa.rst b/Misc/NEWS.d/next/Library/2021-11-11-12-59-10.bpo-28533.68mMZa.rst
deleted file mode 100644
index 4924381..0000000
--- a/Misc/NEWS.d/next/Library/2021-11-11-12-59-10.bpo-28533.68mMZa.rst
+++ /dev/null
@@ -1,2 +0,0 @@
-Remove the ``asyncore`` and ``asynchat`` modules, deprecated in Python 3.6:
-use the :mod:`asyncio` module instead. Patch by Victor Stinner.
diff --git a/Misc/NEWS.d/next/Library/2021-11-11-12-59-49.bpo-28533.LvIFCQ.rst b/Misc/NEWS.d/next/Library/2021-11-11-12-59-49.bpo-28533.LvIFCQ.rst
deleted file mode 100644
index 67fb368..0000000
--- a/Misc/NEWS.d/next/Library/2021-11-11-12-59-49.bpo-28533.LvIFCQ.rst
+++ /dev/null
@@ -1,3 +0,0 @@
-Remove the ``smtpd`` module, deprecated in Python 3.6: the `aiosmtpd
-<https://aiosmtpd.readthedocs.io/>`__ module can be used instead, it is based
-on asyncio. Patch by Victor Stinner.
diff --git a/PCbuild/lib.pyproj b/PCbuild/lib.pyproj
index 7dd40ad..43c570f 100644
--- a/PCbuild/lib.pyproj
+++ b/PCbuild/lib.pyproj
@@ -24,6 +24,7 @@
     <Compile Include="antigravity.py" />
     <Compile Include="argparse.py" />
     <Compile Include="ast.py" />
+    <Compile Include="asynchat.py" />
     <Compile Include="asyncio\base_events.py" />
     <Compile Include="asyncio\base_futures.py" />
     <Compile Include="asyncio\base_subprocess.py" />
@@ -49,6 +50,7 @@
     <Compile Include="asyncio\windows_events.py" />
     <Compile Include="asyncio\windows_utils.py" />
     <Compile Include="asyncio\__init__.py" />
+    <Compile Include="asyncore.py" />
     <Compile Include="base64.py" />
     <Compile Include="bdb.py" />
     <Compile Include="bisect.py" />
@@ -720,6 +722,7 @@
     <Compile Include="shutil.py" />
     <Compile Include="signal.py" />
     <Compile Include="site.py" />
+    <Compile Include="smtpd.py" />
     <Compile Include="smtplib.py" />
     <Compile Include="sndhdr.py" />
     <Compile Include="socket.py" />
@@ -857,6 +860,7 @@
     <Compile Include="test\test_asdl_parser.py" />
     <Compile Include="test\test_ast.py" />
     <Compile Include="test\test_asyncgen.py" />
+    <Compile Include="test\test_asynchat.py" />
     <Compile Include="test\test_asyncio\echo.py" />
     <Compile Include="test\test_asyncio\echo2.py" />
     <Compile Include="test\test_asyncio\echo3.py" />
@@ -878,6 +882,7 @@
     <Compile Include="test\test_asyncio\test_windows_utils.py" />
     <Compile Include="test\test_asyncio\__init__.py" />
     <Compile Include="test\test_asyncio\__main__.py" />
+    <Compile Include="test\test_asyncore.py" />
     <Compile Include="test\test_atexit.py" />
     <Compile Include="test\test_audioop.py" />
     <Compile Include="test\test_augassign.py" />
@@ -1258,6 +1263,7 @@
     <Compile Include="test\test_signal.py" />
     <Compile Include="test\test_site.py" />
     <Compile Include="test\test_slice.py" />
+    <Compile Include="test\test_smtpd.py" />
     <Compile Include="test\test_smtplib.py" />
     <Compile Include="test\test_smtpnet.py" />
     <Compile Include="test\test_sndhdr.py" />
diff --git a/Python/stdlib_module_names.h b/Python/stdlib_module_names.h
index 7d42108..754fa94 100644
--- a/Python/stdlib_module_names.h
+++ b/Python/stdlib_module_names.h
@@ -96,7 +96,9 @@ static const char* _Py_stdlib_module_names[] = {
 "argparse",
 "array",
 "ast",
+"asynchat",
 "asyncio",
+"asyncore",
 "atexit",
 "audioop",
 "base64",
@@ -240,6 +242,7 @@ static const char* _Py_stdlib_module_names[] = {
 "shutil",
 "signal",
 "site",
+"smtpd",
 "smtplib",
 "sndhdr",
 "socket",