Decided to add the telnet library that I wrote long ago (it's still in

the Demos/cwilib directory).  Converted comments to doc strings and
used default arguments instead of *args.  Updated the example.

1 files changed, 424 insertions, 0 deletions

diff --git a/Lib/telnetlib.py b/Lib/telnetlib.py
new file mode 100644
index 0000000..4595426
--- /dev/null
+++ b/Lib/telnetlib.py
@@ -0,0 +1,424 @@
+"""TELNET client class.
+
+Based on RFC 854: TELNET Protocol Specification, by J. Postel and
+J. Reynolds
+
+Example:
+
+>>> from telnetlib import Telnet
+>>> tn = Telnet('www.python.org', 79)   # connect to finger port
+>>> tn.write('guido\r\n')
+>>> print tn.read_all()
+Login       Name               TTY         Idle    When    Where
+guido    Guido van Rossum      pts/2        <Dec  2 11:10> snag.cnri.reston..
+ 
+>>>
+
+Note that read_all() won't read until eof -- it just reads some data
+-- but it guarantees to read at least one byte unless EOF is hit.
+
+It is possible to pass a Telnet object to select.select() in order to
+wait until more data is available.  Note that in this case,
+read_eager() may return '' even if there was data on the socket,
+because the protocol negotiation may have eaten the data.  This is why
+EOFError is needed in some cases to distinguish between "no data" and
+"connection closed" (since the socket also appears ready for reading
+when it is closed).
+
+Bugs:
+- may hang when connection is slow in the middle of an IAC sequence
+
+To do:
+- option negotiation
+
+"""
+
+
+# Imported modules
+import socket
+import select
+import string
+import regsub
+
+# Tunable parameters
+DEBUGLEVEL = 0
+
+# Telnet protocol defaults
+TELNET_PORT = 23
+
+# Telnet protocol characters (don't change)
+IAC  = chr(255) # "Interpret As Command"
+DONT = chr(254)
+DO   = chr(253)
+WONT = chr(252)
+WILL = chr(251)
+theNULL = chr(0)
+
+
+class Telnet:
+
+    """Telnet interface class.
+
+    An instance of this class represents a connection to a telnet
+    server.  The instance is initially not connected; the open()
+    method must be used to establish a connection.  Alternatively, the
+    host name and optional port number can be passed to the
+    constructor, too.
+
+    Don't try to reopen an already connected instance.
+
+    This class has many read_*() methods.  Note that some of them
+    raise EOFError when the end of the connection is read, because
+    they can return an empty string for other reasons.  See the
+    individual doc strings.
+
+    read_until(expected, [timeout])
+        Read until the expected string has been seen, or a timeout is
+	hit (default is no timeout); may block.
+
+    read_all()
+        Read all data until EOF; may block.
+
+    read_some()
+        Read at least one byte or EOF; may block.
+
+    read_very_eager()
+        Read all data available already queued or on the socket,
+	without blocking.
+
+    read_eager()
+        Read either data already queued or some data available on the
+	socket, without blocking.
+
+    read_lazy()
+        Read all data in the raw queue (processing it first), without
+	doing any socket I/O.
+
+    read_very_lazy()
+        Reads all data in the cooked queue, without doing any socket
+	I/O.
+
+    """
+
+    def __init__(self, host=None, port=0):
+	"""Constructor.
+
+	When called without arguments, create an unconnected instance.
+	With a hostname argument, it connects the instance; a port
+	number is optional.
+
+	"""
+	self.debuglevel = DEBUGLEVEL
+	self.host = host
+	self.port = port
+	self.sock = None
+	self.rawq = ''
+	self.irawq = 0
+	self.cookedq = ''
+	self.eof = 0
+	if host:
+	    self.open(host, port)
+
+    def open(self, host, port=0):
+	"""Connect to a host.
+
+	The optional second argument is the port number, which
+	defaults to the standard telnet port (23).
+
+	Don't try to reopen an already connected instance.
+
+	"""
+	self.eof = 0
+	if not port:
+	    port = TELNET_PORT
+	self.host = host
+	self.port = port
+	self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+	self.sock.connect((self.host, self.port))
+
+    def __del__(self):
+	"""Destructor -- close the connection."""
+	self.close()
+
+    def msg(self, msg, *args):
+	"""Print a debug message, when the debug level is > 0.
+
+	If extra arguments are present, they are substituted in the
+	message using the standard string formatting operator.
+
+	"""
+	if self.debuglevel > 0:
+	    print 'Telnet(%s,%d):' % (self.host, self.port),
+	    if args:
+		print msg % args
+	    else:
+		print msg
+
+    def set_debuglevel(self, debuglevel):
+	"""Set the debug level.
+
+	The higher it is, the more debug output you get (on sys.stdout).
+
+	"""
+	self.debuglevel = debuglevel
+
+    def close(self):
+	"""Close the connection."""
+	if self.sock:
+	    self.sock.close()
+	self.sock = 0
+	self.eof = 1
+
+    def get_socket(self):
+	"""Return the socket object used internally."""
+	return self.sock
+
+    def fileno(self):
+	"""Return the fileno() of the socket object used internally."""
+	return self.sock.fileno()
+
+    def write(self, buffer):
+	"""Write a string to the socket, doubling any IAC characters.
+
+	Can block if the connection is blocked.  May raise
+	socket.error if the connection is closed.
+
+	"""
+	if IAC in buffer:
+	    buffer = regsub.gsub(IAC, IAC+IAC, buffer)
+	self.sock.send(buffer)
+
+    def read_until(self, match, timeout=None):
+	"""Read until a given string is encountered or until timeout.
+
+	When no match is found, return whatever is available instead,
+	possibly the empty string.  Raise EOFError if the connection
+	is closed and no cooked data is available.
+
+	"""
+	n = len(match)
+	self.process_rawq()
+	i = string.find(self.cookedq, match)
+	if i >= 0:
+	    i = i+n
+	    buf = self.cookedq[:i]
+	    self.cookedq = self.cookedq[i:]
+	    return buf
+	s_reply = ([self], [], [])
+	s_args = s_reply
+	if timeout is not None:
+	    s_args = s_args + (timeout,)
+	while not self.eof and apply(select.select, s_args) == s_reply:
+	    i = max(0, len(self.cookedq)-n)
+	    self.fill_rawq()
+	    self.process_rawq()
+	    i = string.find(self.cookedq, match, i)
+	    if i >= 0:
+		i = i+n
+		buf = self.cookedq[:i]
+		self.cookedq = self.cookedq[i:]
+		return buf
+	return self.read_very_lazy()
+
+    def read_all(self):
+	"""Read all data until EOF; block until connection closed."""
+	self.process_rawq()
+	while not self.eof:
+	    self.fill_rawq()
+	    self.process_rawq()
+	buf = self.cookedq
+	self.cookedq = ''
+	return buf
+
+    def read_some(self):
+	"""Read at least one byte of cooked data unless EOF is hit.
+
+	Return '' if EOF is hit.  Block if no data is immediately
+	available.
+
+	"""
+	self.process_rawq()
+	while not self.cookedq and not self.eof:
+	    self.fill_rawq()
+	    self.process_rawq()
+	buf = self.cookedq
+	self.cookedq = ''
+	return buf
+
+    def read_very_eager(self):
+	"""Read everything that's possible without blocking in I/O (eager).
+	
+	Raise EOFError if connection closed and no cooked data
+	available.  Return '' if no cooked data available otherwise.
+	Don't block unless in the midst of an IAC sequence.
+
+	"""
+	self.process_rawq()
+	while not self.eof and self.sock_avail():
+	    self.fill_rawq()
+	    self.process_rawq()
+	return self.read_very_lazy()
+
+    def read_eager(self):
+	"""Read readily available data.
+
+	Raise EOFError if connection closed and no cooked data
+	available.  Return '' if no cooked data available otherwise.
+	Don't block unless in the midst of an IAC sequence.
+
+	"""
+	self.process_rawq()
+	while not self.cookedq and not self.eof and self.sock_avail():
+	    self.fill_rawq()
+	    self.process_rawq()
+	return self.read_very_lazy()
+
+    def read_lazy(self):
+	"""Process and return data that's already in the queues (lazy).
+	
+	Raise EOFError if connection closed and no data available.
+	Return '' if no cooked data available otherwise.  Don't block
+	unless in the midst of an IAC sequence.
+
+	"""
+	self.process_rawq()
+	return self.read_very_lazy()
+
+    def read_very_lazy(self):
+	"""Return any data available in the cooked queue (very lazy).
+
+	Raise EOFError if connection closed and no data available.
+	Return '' if no cooked data available otherwise.  Don't block.
+
+	"""
+	buf = self.cookedq
+	self.cookedq = ''
+	if not buf and self.eof and not self.rawq:
+	    raise EOFError, 'telnet connection closed'
+	return buf
+
+    def process_rawq(self):
+	"""Transfer from raw queue to cooked queue.
+
+	Set self.eof when connection is closed.  Don't block unless in
+	the midst of an IAC sequence.
+
+	"""
+	buf = ''
+	try:
+	    while self.rawq:
+		c = self.rawq_getchar()
+		if c == theNULL:
+		    continue
+		if c == "\021":
+		    continue
+		if c != IAC:
+		    buf = buf + c
+		    continue
+		c = self.rawq_getchar()
+		if c == IAC:
+		    buf = buf + c
+		elif c in (DO, DONT):
+		    opt = self.rawq_getchar()
+		    self.msg('IAC %s %d', c == DO and 'DO' or 'DONT', ord(c))
+		    self.sock.send(IAC + WONT + opt)
+		elif c in (WILL, WONT):
+		    opt = self.rawq_getchar()
+		    self.msg('IAC %s %d',
+			     c == WILL and 'WILL' or 'WONT', ord(c))
+		else:
+		    self.msg('IAC %s not recognized' % `c`)
+	except EOFError: # raised by self.rawq_getchar()
+	    pass
+	self.cookedq = self.cookedq + buf
+
+    def rawq_getchar(self):
+	"""Get next char from raw queue.
+
+	Block if no data is immediately available.  Raise EOFError
+	when connection is closed.
+
+	"""
+	if not self.rawq:
+	    self.fill_rawq()
+	    if self.eof:
+		raise EOFError
+	c = self.rawq[self.irawq]
+	self.irawq = self.irawq + 1
+	if self.irawq >= len(self.rawq):
+	    self.rawq = ''
+	    self.irawq = 0
+	return c
+
+    def fill_rawq(self):
+	"""Fill raw queue from exactly one recv() system call.
+
+	Block if no data is immediately available.  Set self.eof when
+	connection is closed.
+
+	"""
+	if self.irawq >= len(self.rawq):
+	    self.rawq = ''
+	    self.irawq = 0
+	# The buffer size should be fairly small so as to avoid quadratic
+	# behavior in process_rawq() above
+	buf = self.sock.recv(50)
+	self.eof = (not buf)
+	self.rawq = self.rawq + buf
+
+    def sock_avail(self):
+	"""Test whether data is available on the socket."""
+	return select.select([self], [], [], 0) == ([self], [], [])
+
+    def interact(self):
+	"""Interaction function, emulates a very dumb telnet client."""
+	import sys, select
+	while 1:
+	    rfd, wfd, xfd = select.select([self, sys.stdin], [], [])
+	    if sys.stdin in rfd:
+		line = sys.stdin.readline()
+		self.write(line)
+	    if self in rfd:
+		try:
+		    text = self.read_eager()
+		except EOFError:
+		    print '*** Connection closed by remote host ***'
+		    break
+		if text:
+		    sys.stdout.write(text)
+		    sys.stdout.flush()
+	self.close()
+
+
+
+def test():
+    """Test program for telnetlib.
+
+    Usage: python telnetlib.py [-d] ... [host [port]]
+
+    Default host is localhost; default port is 23.
+
+    """
+    import sys
+    debuglevel = 0
+    while sys.argv[1:] and sys.argv[1] == '-d':
+	debuglevel = debuglevel+1
+	del sys.argv[1]
+    host = 'localhost'
+    if sys.argv[1:]:
+	host = sys.argv[1]
+    port = 0
+    if sys.argv[2:]:
+	portstr = sys.argv[2]
+	try:
+	    port = int(portstr)
+	except ValueError:
+	    port = socket.getservbyname(portstr, 'tcp')
+    tn = Telnet()
+    tn.set_debuglevel(debuglevel)
+    tn.open(host, port)
+    tn.interact()
+    tn.close()
+
+if __name__ == '__main__':
+    test()