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-'\"
-'\" Copyright (c) 1995-1997 Sun Microsystems, Inc.
-'\" Copyright (c) 1998-2000 by Ajuba Solutions.
-'\" Copyright (c) 2004 ActiveState Corporation.
-'\"
-'\" See the file "license.terms" for information on usage and redistribution
-'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
-'\"
-.TH "http" n 2.9 http "Tcl Bundled Packages"
-.so man.macros
-.BS
-'\" Note: do not modify the .SH NAME line immediately below!
-.SH NAME
-http \- Client-side implementation of the HTTP/1.1 protocol
-.SH SYNOPSIS
-\fBpackage require http ?2.8?\fR
-.\" See Also -useragent option documentation in body!
-.sp
-\fB::http::config ?\fI\-option value\fR ...?
-.sp
-\fB::http::geturl \fIurl\fR ?\fI\-option value\fR ...?
-.sp
-\fB::http::formatQuery\fR \fIkey value\fR ?\fIkey value\fR ...?
-.sp
-\fB::http::quoteString\fR \fIvalue\fR
-.sp
-\fB::http::reset\fR \fItoken\fR ?\fIwhy\fR?
-.sp
-\fB::http::wait \fItoken\fR
-.sp
-\fB::http::status \fItoken\fR
-.sp
-\fB::http::size \fItoken\fR
-.sp
-\fB::http::code \fItoken\fR
-.sp
-\fB::http::ncode \fItoken\fR
-.sp
-\fB::http::meta \fItoken\fR
-.sp
-\fB::http::data \fItoken\fR
-.sp
-\fB::http::error \fItoken\fR
-.sp
-\fB::http::cleanup \fItoken\fR
-.sp
-\fB::http::register \fIproto port command\fR
-.sp
-\fB::http::registerError \fIport\fR ?\fImessage\fR?
-.sp
-\fB::http::unregister \fIproto\fR
-.BE
-.SH DESCRIPTION
-.PP
-The \fBhttp\fR package provides the client side of the HTTP/1.1
-protocol, as defined in RFC 7230 to RFC 7235, which supersede RFC 2616.
-The package implements the GET, POST, and HEAD operations
-of HTTP/1.1. It allows configuration of a proxy host to get through
-firewalls. The package is compatible with the \fBSafesock\fR security
-policy, so it can be used by untrusted applets to do URL fetching from
-a restricted set of hosts. This package can be extended to support
-additional HTTP transport protocols, such as HTTPS, by providing
-a custom \fBsocket\fR command, via \fB::http::register\fR.
-.PP
-The \fB::http::geturl\fR procedure does a HTTP transaction.
-Its \fIoptions \fR determine whether a GET, POST, or HEAD transaction
-is performed.
-The return value of \fB::http::geturl\fR is a token for the transaction.
-The value is also the name of an array in the ::http namespace
-that contains state information about the transaction. The elements
-of this array are described in the \fBSTATE ARRAY\fR section.
-.PP
-If the \fB\-command\fR option is specified, then
-the HTTP operation is done in the background.
-\fB::http::geturl\fR returns immediately after generating the
-HTTP request and the callback is invoked
-when the transaction completes. For this to work, the Tcl event loop
-must be active. In Tk applications this is always true. For pure-Tcl
-applications, the caller can use \fB::http::wait\fR after calling
-\fB::http::geturl\fR to start the event loop.
-.SH COMMANDS
-.TP
-\fB::http::config\fR ?\fIoptions\fR?
-.
-The \fB::http::config\fR command is used to set and query the name of the
-proxy server and port, and the User-Agent name used in the HTTP
-requests. If no options are specified, then the current configuration
-is returned. If a single argument is specified, then it should be one
-of the flags described below. In this case the current value of
-that setting is returned. Otherwise, the options should be a set of
-flags and values that define the configuration:
-.RS
-.TP
-\fB\-accept\fR \fImimetypes\fR
-.
-The Accept header of the request. The default is */*, which means that
-all types of documents are accepted. Otherwise you can supply a
-comma-separated list of mime type patterns that you are
-willing to receive. For example,
-.QW "image/gif, image/jpeg, text/*" .
-.TP
-\fB\-pipeline\fR \fIboolean\fR
-.
-Specifies whether HTTP/1.1 transactions on a persistent socket will be
-pipelined. See the \fBPERSISTENT SOCKETS\fR section for details. The default
-is 1.
-.TP
-\fB\-postfresh\fR \fIboolean\fR
-.
-Specifies whether requests that use the \fBPOST\fR method will always use a
-fresh socket, overriding the \fB-keepalive\fR option of
-command \fBhttp::geturl\fR. See the \fBPERSISTENT SOCKETS\fR section for details.
-The default is 0.
-.TP
-\fB\-proxyhost\fR \fIhostname\fR
-.
-The name of the proxy host, if any. If this value is the
-empty string, the URL host is contacted directly.
-.TP
-\fB\-proxyport\fR \fInumber\fR
-.
-The proxy port number.
-.TP
-\fB\-proxyfilter\fR \fIcommand\fR
-.
-The command is a callback that is made during
-\fB::http::geturl\fR
-to determine if a proxy is required for a given host. One argument, a
-host name, is added to \fIcommand\fR when it is invoked. If a proxy
-is required, the callback should return a two-element list containing
-the proxy server and proxy port. Otherwise the filter should return
-an empty list. The default filter returns the values of the
-\fB\-proxyhost\fR and \fB\-proxyport\fR settings if they are
-non-empty.
-.TP
-\fB\-repost\fR \fIboolean\fR
-.
-Specifies what to do if a POST request over a persistent connection fails
-because the server has half-closed the connection. If boolean \fBtrue\fR, the
-request
-will be automatically retried; if boolean \fBfalse\fR it will not, and the
-application
-that uses \fBhttp::geturl\fR is expected to seek user confirmation before
-retrying the POST. The value \fBtrue\fR should be used only under certain
-conditions. See the \fBPERSISTENT SOCKETS\fR section for details. The
-default is 0.
-.TP
-\fB\-urlencoding\fR \fIencoding\fR
-.
-The \fIencoding\fR used for creating the x-url-encoded URLs with
-\fB::http::formatQuery\fR and \fB::http::quoteString\fR.
-The default is \fButf-8\fR, as specified by RFC
-2718. Prior to http 2.5 this was unspecified, and that behavior can be
-returned by specifying the empty string (\fB{}\fR), although
-\fIiso8859-1\fR is recommended to restore similar behavior but without the
-\fB::http::formatQuery\fR or \fB::http::quoteString\fR
-throwing an error processing non-latin-1 characters.
-.TP
-\fB\-useragent\fR \fIstring\fR
-.
-The value of the User-Agent header in the HTTP request. In an unsafe
-interpreter, the default value depends upon the operating system, and
-the version numbers of \fBhttp\fR and \fBTcl\fR, and is (for example)
-.QW "\fBMozilla/5.0 (Windows; U; Windows NT 10.0) http/2.8.12 Tcl/8.6.8\fR" .
-A safe interpreter cannot determine its operating system, and so the default
-in a safe interpreter is to use a Windows 10 value with the current version
-numbers of \fBhttp\fR and \fBTcl\fR.
-.TP
-\fB\-zip\fR \fIboolean\fR
-.
-If the value is boolean \fBtrue\fR, then by default requests will send a header
-.QW "\fBAccept-Encoding: gzip,deflate,compress\fR" .
-If the value is boolean \fBfalse\fR, then by default this header will not be sent.
-In either case the default can be overridden for an individual request by
-supplying a custom \fBAccept-Encoding\fR header in the \fB-headers\fR option
-of \fBhttp::geturl\fR. The default is 1.
-.RE
-.TP
-\fB::http::geturl\fR \fIurl\fR ?\fIoptions\fR?
-.
-The \fB::http::geturl\fR command is the main procedure in the package.
-The \fB\-query\fR option causes a POST operation and
-the \fB\-validate\fR option causes a HEAD operation;
-otherwise, a GET operation is performed. The \fB::http::geturl\fR command
-returns a \fItoken\fR value that can be used to get
-information about the transaction. See the \fBSTATE ARRAY\fR and
-\fBERRORS\fR section for
-details. The \fB::http::geturl\fR command blocks until the operation
-completes, unless the \fB\-command\fR option specifies a callback
-that is invoked when the HTTP transaction completes.
-\fB::http::geturl\fR takes several options:
-.RS
-.TP
-\fB\-binary\fR \fIboolean\fR
-.
-Specifies whether to force interpreting the URL data as binary. Normally
-this is auto-detected (anything not beginning with a \fBtext\fR content
-type or whose content encoding is \fBgzip\fR or \fBcompress\fR is
-considered binary data).
-.TP
-\fB\-blocksize\fR \fIsize\fR
-.
-The block size used when reading the URL.
-At most \fIsize\fR bytes are read at once. After each block, a call to the
-\fB\-progress\fR callback is made (if that option is specified).
-.TP
-\fB\-channel\fR \fIname\fR
-.
-Copy the URL contents to channel \fIname\fR instead of saving it in
-\fBstate(body)\fR.
-.TP
-\fB\-command\fR \fIcallback\fR
-.
-Invoke \fIcallback\fR after the HTTP transaction completes.
-This option causes \fB::http::geturl\fR to return immediately.
-The \fIcallback\fR gets an additional argument that is the \fItoken\fR returned
-from \fB::http::geturl\fR. This token is the name of an array that is
-described in the \fBSTATE ARRAY\fR section. Here is a template for the
-callback:
-.RS
-.PP
-.CS
-proc httpCallback {token} {
- upvar #0 $token state
- # Access state as a Tcl array
-}
-.CE
-.RE
-.TP
-\fB\-handler\fR \fIcallback\fR
-.
-Invoke \fIcallback\fR whenever HTTP data is available; if present, nothing
-else will be done with the HTTP data. This procedure gets two additional
-arguments: the socket for the HTTP data and the \fItoken\fR returned from
-\fB::http::geturl\fR. The token is the name of a global array that is
-described in the \fBSTATE ARRAY\fR section. The procedure is expected
-to return the number of bytes read from the socket. Here is a
-template for the callback:
-.RS
-.PP
-.CS
-proc httpHandlerCallback {socket token} {
- upvar #0 $token state
- # Access socket, and state as a Tcl array
- # For example...
- ...
- set data [read $socket 1000]
- set nbytes [string length $data]
- ...
- return $nbytes
-}
-.CE
-.RE
-.TP
-\fB\-headers\fR \fIkeyvaluelist\fR
-.
-This option is used to add headers not already specified
-by \fB::http::config\fR to the HTTP request. The
-\fIkeyvaluelist\fR argument must be a list with an even number of
-elements that alternate between keys and values. The keys become
-header field names. Newlines are stripped from the values so the
-header cannot be corrupted. For example, if \fIkeyvaluelist\fR is
-\fBPragma no-cache\fR then the following header is included in the
-HTTP request:
-.RS
-.PP
-.CS
-Pragma: no-cache
-.CE
-.RE
-.TP
-\fB\-keepalive\fR \fIboolean\fR
-.
-If boolean \fBtrue\fR, attempt to keep the connection open for servicing
-multiple requests. Default is 0.
-.TP
-\fB\-method\fR \fItype\fR
-.
-Force the HTTP request method to \fItype\fR. \fB::http::geturl\fR will
-auto-select GET, POST or HEAD based on other options, but this option
-enables choices like PUT and DELETE for webdav support.
-.TP
-\fB\-myaddr\fR \fIaddress\fR
-.
-Pass an specific local address to the underlying \fBsocket\fR call in case
-multiple interfaces are available.
-.TP
-\fB\-progress\fR \fIcallback\fR
-.
-The \fIcallback\fR is made after each transfer of data from the URL.
-The callback gets three additional arguments: the \fItoken\fR from
-\fB::http::geturl\fR, the expected total size of the contents from the
-\fBContent-Length\fR meta-data, and the current number of bytes
-transferred so far. The expected total size may be unknown, in which
-case zero is passed to the callback. Here is a template for the
-progress callback:
-.RS
-.PP
-.CS
-proc httpProgress {token total current} {
- upvar #0 $token state
-}
-.CE
-.RE
-.TP
-\fB\-protocol\fR \fIversion\fR
-.
-Select the HTTP protocol version to use. This should be 1.0 or 1.1 (the
-default). Should only be necessary for servers that do not understand or
-otherwise complain about HTTP/1.1.
-.TP
-\fB\-query\fR \fIquery\fR
-.
-This flag causes \fB::http::geturl\fR to do a POST request that passes the
-\fIquery\fR to the server. The \fIquery\fR must be an x-url-encoding
-formatted query. The \fB::http::formatQuery\fR procedure can be used to
-do the formatting.
-.TP
-\fB\-queryblocksize\fR \fIsize\fR
-.
-The block size used when posting query data to the URL.
-At most
-\fIsize\fR
-bytes are written at once. After each block, a call to the
-\fB\-queryprogress\fR
-callback is made (if that option is specified).
-.TP
-\fB\-querychannel\fR \fIchannelID\fR
-.
-This flag causes \fB::http::geturl\fR to do a POST request that passes the
-data contained in \fIchannelID\fR to the server. The data contained in
-\fIchannelID\fR must be an x-url-encoding
-formatted query unless the \fB\-type\fR option below is used.
-If a Content-Length header is not specified via the \fB\-headers\fR options,
-\fB::http::geturl\fR attempts to determine the size of the post data
-in order to create that header. If it is
-unable to determine the size, it returns an error.
-.TP
-\fB\-queryprogress\fR \fIcallback\fR
-.
-The \fIcallback\fR is made after each transfer of data to the URL
-(i.e. POST) and acts exactly like the \fB\-progress\fR option (the
-callback format is the same).
-.TP
-\fB\-strict\fR \fIboolean\fR
-.
-Whether to enforce RFC 3986 URL validation on the request. Default is 1.
-.TP
-\fB\-timeout\fR \fImilliseconds\fR
-.
-If \fImilliseconds\fR is non-zero, then \fB::http::geturl\fR sets up a timeout
-to occur after the specified number of milliseconds.
-A timeout results in a call to \fB::http::reset\fR and to
-the \fB\-command\fR callback, if specified.
-The return value of \fB::http::status\fR is \fBtimeout\fR
-after a timeout has occurred.
-.TP
-\fB\-type\fR \fImime-type\fR
-.
-Use \fImime-type\fR as the \fBContent-Type\fR value, instead of the
-default value (\fBapplication/x-www-form-urlencoded\fR) during a
-POST operation.
-.TP
-\fB\-validate\fR \fIboolean\fR
-.
-If \fIboolean\fR is non-zero, then \fB::http::geturl\fR does an HTTP HEAD
-request. This request returns meta information about the URL, but the
-contents are not returned. The meta information is available in the
-\fBstate(meta) \fR variable after the transaction. See the
-\fBSTATE ARRAY\fR section for details.
-.RE
-.TP
-\fB::http::formatQuery\fR \fIkey value\fR ?\fIkey value\fR ...?
-.
-This procedure does x-url-encoding of query data. It takes an even
-number of arguments that are the keys and values of the query. It
-encodes the keys and values, and generates one string that has the
-proper & and = separators. The result is suitable for the
-\fB\-query\fR value passed to \fB::http::geturl\fR.
-.TP
-\fB::http::quoteString\fR \fIvalue\fR
-.
-This procedure does x-url-encoding of string. It takes a single argument and
-encodes it.
-.TP
-\fB::http::reset\fR \fItoken\fR ?\fIwhy\fR?
-.
-This command resets the HTTP transaction identified by \fItoken\fR, if any.
-This sets the \fBstate(status)\fR value to \fIwhy\fR, which defaults to
-\fBreset\fR, and then calls the registered \fB\-command\fR callback.
-.TP
-\fB::http::wait\fR \fItoken\fR
-.
-This is a convenience procedure that blocks and waits for the
-transaction to complete. This only works in trusted code because it
-uses \fBvwait\fR. Also, it is not useful for the case where
-\fB::http::geturl\fR is called \fIwithout\fR the \fB\-command\fR option
-because in this case the \fB::http::geturl\fR call does not return
-until the HTTP transaction is complete, and thus there is nothing to
-wait for.
-.TP
-\fB::http::data\fR \fItoken\fR
-.
-This is a convenience procedure that returns the \fBbody\fR element
-(i.e., the URL data) of the state array.
-.TP
-\fB::http::error\fR \fItoken\fR
-.
-This is a convenience procedure that returns the \fBerror\fR element
-of the state array.
-.TP
-\fB::http::status\fR \fItoken\fR
-.
-This is a convenience procedure that returns the \fBstatus\fR element of
-the state array.
-.TP
-\fB::http::code\fR \fItoken\fR
-.
-This is a convenience procedure that returns the \fBhttp\fR element of the
-state array.
-.TP
-\fB::http::ncode\fR \fItoken\fR
-.
-This is a convenience procedure that returns just the numeric return
-code (200, 404, etc.) from the \fBhttp\fR element of the state array.
-.TP
-\fB::http::size\fR \fItoken\fR
-.
-This is a convenience procedure that returns the \fBcurrentsize\fR
-element of the state array, which represents the number of bytes
-received from the URL in the \fB::http::geturl\fR call.
-.TP
-\fB::http::meta\fR \fItoken\fR
-.
-This is a convenience procedure that returns the \fBmeta\fR
-element of the state array which contains the HTTP response
-headers. See below for an explanation of this element.
-.TP
-\fB::http::cleanup\fR \fItoken\fR
-.
-This procedure cleans up the state associated with the connection
-identified by \fItoken\fR. After this call, the procedures
-like \fB::http::data\fR cannot be used to get information
-about the operation. It is \fIstrongly\fR recommended that you call
-this function after you are done with a given HTTP request. Not doing
-so will result in memory not being freed, and if your app calls
-\fB::http::geturl\fR enough times, the memory leak could cause a
-performance hit...or worse.
-.TP
-\fB::http::register\fR \fIproto port command\fR
-.
-This procedure allows one to provide custom HTTP transport types
-such as HTTPS, by registering a prefix, the default port, and the
-command to execute to create the Tcl \fBchannel\fR. E.g.:
-.RS
-.PP
-.CS
-package require http
-package require tls
-
-::http::register https 443 ::tls::socket
-
-set token [::http::geturl https://my.secure.site/]
-.CE
-.RE
-.TP
-\fB::http::registerError\fR \fIport\fR ?\fImessage\fR?
-.
-This procedure allows a registered protocol handler to deliver an error
-message for use by \fBhttp\fR. Calling this command does not raise an
-error. The command is useful when a registered protocol detects an problem
-(for example, an invalid TLS certificate) that will cause an error to
-propagate to \fBhttp\fR. The command allows \fBhttp\fR to provide a
-precise error message rather than a general one. The command returns the
-value provided by the last call with argument \fImessage\fR, or the empty
-string if no such call has been made.
-.TP
-\fB::http::unregister\fR \fIproto\fR
-.
-This procedure unregisters a protocol handler that was previously
-registered via \fB::http::register\fR, returning a two-item list of
-the default port and handler command that was previously installed
-(via \fB::http::register\fR) if there was such a handler, and an error if
-there was no such handler.
-.SH ERRORS
-The \fB::http::geturl\fR procedure will raise errors in the following cases:
-invalid command line options,
-an invalid URL,
-a URL on a non-existent host,
-or a URL at a bad port on an existing host.
-These errors mean that it
-cannot even start the network transaction.
-It will also raise an error if it gets an I/O error while
-writing out the HTTP request header.
-For synchronous \fB::http::geturl\fR calls (where \fB\-command\fR is
-not specified), it will raise an error if it gets an I/O error while
-reading the HTTP reply headers or data. Because \fB::http::geturl\fR
-does not return a token in these cases, it does all the required
-cleanup and there is no issue of your app having to call
-\fB::http::cleanup\fR.
-.PP
-For asynchronous \fB::http::geturl\fR calls, all of the above error
-situations apply, except that if there is any error while reading the
-HTTP reply headers or data, no exception is thrown. This is because
-after writing the HTTP headers, \fB::http::geturl\fR returns, and the
-rest of the HTTP transaction occurs in the background. The command
-callback can check if any error occurred during the read by calling
-\fB::http::status\fR to check the status and if its \fIerror\fR,
-calling \fB::http::error\fR to get the error message.
-.PP
-Alternatively, if the main program flow reaches a point where it needs
-to know the result of the asynchronous HTTP request, it can call
-\fB::http::wait\fR and then check status and error, just as the
-callback does.
-.PP
-In any case, you must still call
-\fB::http::cleanup\fR to delete the state array when you are done.
-.PP
-There are other possible results of the HTTP transaction
-determined by examining the status from \fB::http::status\fR.
-These are described below.
-.TP
-\fBok\fR
-.
-If the HTTP transaction completes entirely, then status will be \fBok\fR.
-However, you should still check the \fB::http::code\fR value to get
-the HTTP status. The \fB::http::ncode\fR procedure provides just
-the numeric error (e.g., 200, 404 or 500) while the \fB::http::code\fR
-procedure returns a value like
-.QW "HTTP 404 File not found" .
-.TP
-\fBeof\fR
-.
-If the server closes the socket without replying, then no error
-is raised, but the status of the transaction will be \fBeof\fR.
-.TP
-\fBerror\fR
-.
-The error message will also be stored in the \fBerror\fR status
-array element, accessible via \fB::http::error\fR.
-.PP
-Another error possibility is that \fB::http::geturl\fR is unable to
-write all the post query data to the server before the server
-responds and closes the socket.
-The error message is saved in the \fBposterror\fR status array
-element and then \fB::http::geturl\fR attempts to complete the
-transaction.
-If it can read the server's response
-it will end up with an \fBok\fR status, otherwise it will have
-an \fBeof\fR status.
-.SH "STATE ARRAY"
-The \fB::http::geturl\fR procedure returns a \fItoken\fR that can be used to
-get to the state of the HTTP transaction in the form of a Tcl array.
-Use this construct to create an easy-to-use array variable:
-.PP
-.CS
-upvar #0 $token state
-.CE
-.PP
-Once the data associated with the URL is no longer needed, the state
-array should be unset to free up storage.
-The \fB::http::cleanup\fR procedure is provided for that purpose.
-The following elements of
-the array are supported:
-.RS
-.TP
-\fBbinary\fR
-.
-This is boolean \fBtrue\fR if (after decoding any compression specified
-by the
-.QW "Content-Encoding"
-response header) the HTTP response is binary. It is boolean \fBfalse\fR
-if the HTTP response is text.
-.TP
-\fBbody\fR
-.
-The contents of the URL. This will be empty if the \fB\-channel\fR
-option has been specified. This value is returned by the \fB::http::data\fR command.
-.TP
-\fBcharset\fR
-.
-The value of the charset attribute from the \fBContent-Type\fR meta-data
-value. If none was specified, this defaults to the RFC standard
-\fBiso8859-1\fR, or the value of \fB$::http::defaultCharset\fR. Incoming
-text data will be automatically converted from this charset to utf-8.
-.TP
-\fBcoding\fR
-.
-A copy of the \fBContent-Encoding\fR meta-data value.
-.TP
-\fBcurrentsize\fR
-.
-The current number of bytes fetched from the URL.
-This value is returned by the \fB::http::size\fR command.
-.TP
-\fBerror\fR
-.
-If defined, this is the error string seen when the HTTP transaction
-was aborted.
-.TP
-\fBhttp\fR
-.
-The HTTP status reply from the server. This value
-is returned by the \fB::http::code\fR command. The format of this value is:
-.RS
-.PP
-.CS
-\fIHTTP/1.1 code string\fR
-.CE
-.PP
-The \fIcode\fR is a three-digit number defined in the HTTP standard.
-A code of 200 is OK. Codes beginning with 4 or 5 indicate errors.
-Codes beginning with 3 are redirection errors. In this case the
-\fBLocation\fR meta-data specifies a new URL that contains the
-requested information.
-.RE
-.TP
-\fBmeta\fR
-.
-The HTTP protocol returns meta-data that describes the URL contents.
-The \fBmeta\fR element of the state array is a list of the keys and
-values of the meta-data. This is in a format useful for initializing
-an array that just contains the meta-data:
-.RS
-.PP
-.CS
-array set meta $state(meta)
-.CE
-.PP
-Some of the meta-data keys are listed below, but the HTTP standard defines
-more, and servers are free to add their own.
-.TP
-\fBContent-Type\fR
-.
-The type of the URL contents. Examples include \fBtext/html\fR,
-\fBimage/gif,\fR \fBapplication/postscript\fR and
-\fBapplication/x-tcl\fR.
-.TP
-\fBContent-Length\fR
-.
-The advertised size of the contents. The actual size obtained by
-\fB::http::geturl\fR is available as \fBstate(currentsize)\fR.
-.TP
-\fBLocation\fR
-.
-An alternate URL that contains the requested data.
-.RE
-.TP
-\fBposterror\fR
-.
-The error, if any, that occurred while writing
-the post query data to the server.
-.TP
-\fBstatus\fR
-.
-Either \fBok\fR, for successful completion, \fBreset\fR for
-user-reset, \fBtimeout\fR if a timeout occurred before the transaction
-could complete, or \fBerror\fR for an error condition. During the
-transaction this value is the empty string.
-.TP
-\fBtotalsize\fR
-.
-A copy of the \fBContent-Length\fR meta-data value.
-.TP
-\fBtype\fR
-.
-A copy of the \fBContent-Type\fR meta-data value.
-.TP
-\fBurl\fR
-.
-The requested URL.
-.RE
-.SH "PERSISTENT CONNECTIONS"
-.PP
-.SS "BASICS"
-.PP
-See RFC 7230 Sec 6, which supersedes RFC 2616 Sec 8.1.
-.PP
-A persistent connection allows multiple HTTP/1.1 transactions to be
-carried over the same TCP connection. Pipelining allows a
-client to make multiple requests over a persistent connection without
-waiting for each response. The server sends responses in the same order
-that the requests were received.
-.PP
-If a POST request fails to complete, typically user confirmation is
-needed before sending the request again. The user may wish to verify
-whether the server was modified by the failed POST request, before
-sending the same request again.
-.PP
-A HTTP request will use a persistent socket if the call to
-\fBhttp::geturl\fR has the option \fB-keepalive true\fR. It will use
-pipelining where permitted if the \fBhttp::config\fR option
-\fB-pipeline\fR is boolean \fBtrue\fR (its default value).
-.PP
-The http package maintains no more than one persistent connection to each
-server (i.e. each value of
-.QW "domain:port" ).
-If \fBhttp::geturl\fR is called to make a request over a persistent
-connection while the connection is busy with another request, the new
-request will be held in a queue until the connection is free.
-.PP
-The http package does not support HTTP/1.0 persistent connections
-controlled by the \fBKeep-Alive\fR header.
-.SS "SPECIAL CASES"
-.PP
-This subsection discusses issues related to closure of the
-persistent connection by the server, automatic retry of failed requests,
-the special treatment necessary for POST requests, and the options for
-dealing with these cases.
-.PP
-In accordance with RFC 7230, \fBhttp::geturl\fR does not pipeline
-requests that use the POST method. If a POST uses a persistent
-connection and is not the first request on that connection,
-\fBhttp::geturl\fR waits until it has received the response for the previous
-request; or (if \fBhttp::config\fR option \fB-postfresh\fR is boolean \fBtrue\fR) it
-uses a new connection for each POST.
-.PP
-If the server is processing a number of pipelined requests, and sends a
-response header
-.QW "\fBConnection: close\fR"
-with one of the responses (other than the last), then subsequent responses
-are unfulfilled. \fBhttp::geturl\fR will send the unfulfilled requests again
-over a new connection.
-.PP
-A difficulty arises when a HTTP client sends a request over a persistent
-connection that has been idle for a while. The HTTP server may
-half-close an apparently idle connection while the client is sending a
-request, but before the request arrives at the server: in this case (an
-.QW "asynchronous close event" )
-the request will fail. The difficulty arises because the client cannot
-be certain whether the POST modified the state of the server. For HEAD or
-GET requests, \fBhttp::geturl\fR opens another connection and retransmits
-the failed request. However, if the request was a POST, RFC 7230 forbids
-automatic retry by default, suggesting either user confirmation, or
-confirmation by user-agent software that has semantic understanding of
-the application. The \fBhttp::config\fR option \fB-repost\fR allows for
-either possibility.
-.PP
-Asynchronous close events can occur only in a short interval of time. The
-\fBhttp\fR package monitors each persistent connection for closure by the
-server. Upon detection, the connection is also closed at the client end,
-and subsequent requests will use a fresh connection.
-.PP
-If the \fBhttp::geturl\fR command is called with option \fB-keepalive true\fR,
-then it will both try to use an existing persistent connection
-(if one is available), and it will send the server a
-.QW "\fBConnection: keep-alive\fR"
-request header asking to keep the connection open for future requests.
-.PP
-The \fBhttp::config\fR options \fB-pipeline\fR, \fB-postfresh\fR, and
-\fB-repost\fR relate to persistent connections.
-.PP
-Option \fB-pipeline\fR, if boolean \fBtrue\fR, will pipeline GET and HEAD requests
-made
-over a persistent connection. POST requests will not be pipelined - if the
-POST is not the first transaction on the connection, its request will not
-be sent until the previous response has finished. GET and HEAD requests
-made after a POST will not be sent until the POST response has been
-delivered, and will not be sent if the POST fails.
-.PP
-Option \fB-postfresh\fR, if boolean \fBtrue\fR, will override the \fBhttp::geturl\fR option
-\fB-keepalive\fR, and always open a fresh connection for a POST request.
-.PP
-Option \fB-repost\fR, if \fBtrue\fR, permits automatic retry of a POST request
-that fails because it uses a persistent connection that the server has
-half-closed (an
-.QW "asynchronous close event" ).
-Subsequent GET and HEAD requests in a failed pipeline will also be retried.
-\fIThe -repost option should be used only if the application understands
-that the retry is appropriate\fR - specifically, the application must know
-that if the failed POST successfully modified the state of the server, a repeat POST
-would have no adverse effect.
-.SH EXAMPLE
-.PP
-This example creates a procedure to copy a URL to a file while printing a
-progress meter, and prints the meta-data associated with the URL.
-.PP
-.CS
-proc httpcopy { url file {chunk 4096} } {
- set out [open $file w]
- set token [\fB::http::geturl\fR $url -channel $out \e
- -progress httpCopyProgress -blocksize $chunk]
- close $out
-
- # This ends the line started by httpCopyProgress
- puts stderr ""
-
- upvar #0 $token state
- set max 0
- foreach {name value} $state(meta) {
- if {[string length $name] > $max} {
- set max [string length $name]
- }
- if {[regexp -nocase ^location$ $name]} {
- # Handle URL redirects
- puts stderr "Location:$value"
- return [httpcopy [string trim $value] $file $chunk]
- }
- }
- incr max
- foreach {name value} $state(meta) {
- puts [format "%-*s %s" $max $name: $value]
- }
-
- return $token
-}
-proc httpCopyProgress {args} {
- puts -nonewline stderr .
- flush stderr
-}
-.CE
-.SH "SEE ALSO"
-safe(n), socket(n), safesock(n)
-.SH KEYWORDS
-internet, security policy, socket, www
-'\" Local Variables:
-'\" mode: nroff
-'\" End: