+++ /dev/null
-'\"
-'\" Copyright (c) 1996 Sun Microsystems, Inc.
-'\" Copyright (c) 1998-1999 by Scriptics Corporation.
-'\"
-'\" See the file "license.terms" for information on usage and redistribution
-'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
-'\"
-.TH socket n 8.6 Tcl "Tcl Built-In Commands"
-.so man.macros
-.BS
-'\" Note: do not modify the .SH NAME line immediately below!
-.SH NAME
-socket \- Open a TCP network connection
-.SH SYNOPSIS
-.sp
-\fBsocket \fR?\fIoptions\fR? \fIhost port\fR
-.sp
-\fBsocket\fR \fB\-server \fIcommand\fR ?\fIoptions\fR? \fIport\fR
-.BE
-.SH DESCRIPTION
-.PP
-This command opens a network socket and returns a channel identifier
-that may be used in future invocations of commands like \fBread\fR,
-\fBputs\fR and \fBflush\fR. At present only the TCP network protocol
-is supported over IPv4 and IPv6; future releases may include support
-for additional protocols. The \fBsocket\fR command may be used to
-open either the client or server side of a connection, depending on
-whether the \fB\-server\fR switch is specified.
-.PP
-Note that the default encoding for \fIall\fR sockets is the system
-encoding, as returned by \fBencoding system\fR. Most of the time, you
-will need to use \fBchan configure\fR to alter this to something else,
-such as \fIutf\-8\fR (ideal for communicating with other Tcl
-processes) or \fIiso8859\-1\fR (useful for many network protocols,
-especially the older ones).
-.SH "CLIENT SOCKETS"
-.PP
-If the \fB\-server\fR option is not specified, then the client side of a
-connection is opened and the command returns a channel identifier
-that can be used for both reading and writing.
-\fIPort\fR and \fIhost\fR specify a port
-to connect to; there must be a server accepting connections on
-this port. \fIPort\fR is an integer port number
-(or service name, where supported and understood by the host operating
-system) and \fIhost\fR
-is either a domain-style name such as \fBwww.tcl.tk\fR or
-a numerical IPv4 or IPv6 address such as \fB127.0.0.1\fR or \fB2001:DB8::1\fR.
-Use \fIlocalhost\fR to refer to the host on which the command is invoked.
-.PP
-The following options may also be present before \fIhost\fR
-to specify additional information about the connection:
-.TP
-\fB\-myaddr\fI addr\fR
-.
-\fIAddr\fR gives the domain-style name or numerical IP address of
-the client-side network interface to use for the connection.
-This option may be useful if the client machine has multiple network
-interfaces. If the option is omitted then the client-side interface
-will be chosen by the system software.
-.TP
-\fB\-myport\fI port\fR
-.
-\fIPort\fR specifies an integer port number (or service name, where
-supported and understood by the host operating system) to use for the
-client's
-side of the connection. If this option is omitted, the client's
-port number will be chosen at random by the system software.
-.TP
-\fB\-async\fR
-.
-This option will cause the client socket to be connected
-asynchronously. This means that the socket will be created immediately
-but may not yet be connected to the server, when the call to
-\fBsocket\fR returns.
-.RS
-.PP
-When a \fBgets\fR or \fBflush\fR is done on the socket before the
-connection attempt succeeds or fails, if the socket is in blocking
-mode, the operation will wait until the connection is completed or
-fails. If the socket is in nonblocking mode and a \fBgets\fR or
-\fBflush\fR is done on the socket before the connection attempt
-succeeds or fails, the operation returns immediately and
-\fBfblocked\fR on the socket returns 1. Synchronous client sockets may
-be switched (after they have connected) to operating in asynchronous
-mode using:
-.PP
-.CS
-\fBchan configure \fIchan \fB\-blocking 0\fR
-.CE
-.PP
-See the \fBchan configure\fR command for more details.
-.PP
-The Tcl event loop should be running while an asynchronous connection
-is in progress, because it may have to do several connection attempts
-in the background. Running the event loop also allows you to set up a
-writable channel event on the socket to get notified when the
-asynchronous connection has succeeded or failed. See the \fBvwait\fR
-and the \fBchan\fR commands for more details on the event loop and
-channel events.
-.PP
-The \fBchan configure\fR option \fB-connecting\fR may be used to check if the connect is still running. To verify a successful connect, the option \fB-error\fR may be checked when \fB-connecting\fR returned 0.
-.PP
-Operation without the event queue requires at the moment calls to \fBchan configure\fR to advance the internal state machine.
-.RE
-.SH "SERVER SOCKETS"
-.PP
-If the \fB\-server\fR option is specified then the new socket will be
-a server that listens on the given \fIport\fR (either an integer or a
-service name, where supported and understood by the host operating
-system; if \fIport\fR is zero, the operating system will allocate a
-free port to the server socket which may be discovered by using
-\fBchan configure\fR to read the \fB\-sockname\fR option). If the host
-supports both, IPv4 and IPv6, the socket will listen on both address
-families. Tcl will automatically accept connections to the given port.
-For each connection Tcl will create a new channel that may be used to
-communicate with the client. Tcl then invokes \fIcommand\fR (properly
-a command prefix list, see the \fBEXAMPLES\fR below) with three
-additional arguments: the name of the new channel, the address, in
-network address notation, of the client's host, and the client's port
-number.
-.PP
-The following additional option may also be specified before \fIport\fR:
-.TP
-\fB\-myaddr\fI addr\fR
-.
-\fIAddr\fR gives the domain-style name or numerical IP address of the
-server-side network interface to use for the connection. This option
-may be useful if the server machine has multiple network interfaces.
-If the option is omitted then the server socket is bound to the
-wildcard address so that it can accept connections from any
-interface. If \fIaddr\fR is a domain name that resolves to multiple IP
-addresses that are available on the local machine, the socket will
-listen on all of them.
-.PP
-Server channels cannot be used for input or output; their sole use is to
-accept new client connections. The channels created for each incoming
-client connection are opened for input and output. Closing the server
-channel shuts down the server so that no new connections will be
-accepted; however, existing connections will be unaffected.
-.PP
-Server sockets depend on the Tcl event mechanism to find out when
-new connections are opened. If the application does not enter the
-event loop, for example by invoking the \fBvwait\fR command or
-calling the C procedure \fBTcl_DoOneEvent\fR, then no connections
-will be accepted.
-.PP
-If \fIport\fR is specified as zero, the operating system will allocate
-an unused port for use as a server socket. The port number actually
-allocated may be retrieved from the created server socket using the
-\fBchan configure\fR command to retrieve the \fB\-sockname\fR option as
-described below.
-.SH "CONFIGURATION OPTIONS"
-.PP
-The \fBchan configure\fR command can be used to query several readonly
-configuration options for socket channels:
-.TP
-\fB\-error\fR
-.
-This option gets the current error status of the given socket. This
-is useful when you need to determine if an asynchronous connect
-operation succeeded. If there was an error, the error message is
-returned. If there was no error, an empty string is returned.
-.RS
-.PP
-Note that the error status is reset by the read operation; this mimics
-the underlying getsockopt(SO_ERROR) call.
-.RE
-.TP
-\fB\-sockname\fR
-.
-For client sockets (including the channels that get created when a
-client connects to a server socket) this option returns a list of
-three elements, the address, the host name and the port number for the
-socket. If the host name cannot be computed, the second element is
-identical to the address, the first element of the list.
-.RS
-.PP
-For server sockets this option returns a list of a multiple of three
-elements each group of which have the same meaning as described
-above. The list contains more than one group when the server socket
-was created without \fB\-myaddr\fR or with the argument to
-\fB\-myaddr\fR being a domain name that resolves multiple IP addresses
-that are local to the invoking host.
-.RE
-.TP
-\fB\-peername\fR
-.
-This option is not supported by server sockets. For client and accepted
-sockets, this option returns a list of three elements; these are the
-address, the host name and the port to which the peer socket is connected
-or bound. If the host name cannot be computed, the second element of the
-list is identical to the address, its first element.
-.TP
-\fB\-connecting\fR
-.
-This option is not supported by server sockets. For client sockets, this option returns 1 if an asyncroneous connect is still in progress, 0 otherwise.
-.PP
-.SH "EXAMPLES"
-.PP
-Here is a very simple time server:
-.PP
-.CS
-proc Server {startTime channel clientaddr clientport} {
- puts "Connection from $clientaddr registered"
- set now [clock seconds]
- puts $channel [clock format $now]
- puts $channel "[expr {$now - $startTime}] since start"
- close $channel
-}
-
-\fBsocket -server\fR [list Server [clock seconds]] 9900
-vwait forever
-.CE
-.PP
-And here is the corresponding client to talk to the server and extract
-some information:
-.PP
-.CS
-set server localhost
-set sockChan [\fBsocket\fR $server 9900]
-gets $sockChan line1
-gets $sockChan line2
-close $sockChan
-puts "The time on $server is $line1"
-puts "That is [lindex $line2 0]s since the server started"
-.CE
-.SH "HISTORY"
-Support for IPv6 was added in Tcl 8.6.
-.SH "SEE ALSO"
-chan(n), flush(n), open(n), read(n)
-.SH KEYWORDS
-asynchronous I/O, bind, channel, connection, domain name, host, network address, socket, tcp
-'\" Local Variables:
-'\" mode: nroff
-'\" End:
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