126 lines
5.2 KiB
Plaintext
126 lines
5.2 KiB
Plaintext
'\"
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'\" Copyright (c) 1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" SCCS: @(#) socket.n 1.13 96/04/05 12:05:26
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.so man.macros
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.TH socket n 7.5 Tcl "Tcl Built-In Commands"
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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socket \- Open a TCP network connection
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.SH SYNOPSIS
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.sp
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\fBsocket \fR?\fIoptions\fR? \fIhost port\fR
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.sp
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\fBsocket \fB\-server \fIcommand\fR ?\fIoptions\fR? \fIport\fR
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.BE
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.SH DESCRIPTION
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.PP
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This command opens a network socket and returns a channel
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identifier that may be used in future invocations of commands like
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\fBread\fR, \fBputs\fR and \fBflush\fR.
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At present only the TCP network protocol is supported; future
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releases may include support for additional protocols.
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The \fBsocket\fR command may be used to open either the client or
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server side of a connection, depending on whether the \fB\-server\fR
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switch is specified.
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.SH "CLIENT SOCKETS"
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.PP
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If the \fB\-server\fR option is not specified, then the client side of a
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connection is opened and the command returns a channel identifier
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that can be used for both reading and writing.
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\fIPort\fR and \fIhost\fR specify a port
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to connect to; there must be a server accepting connections on
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this port. \fIPort\fR is an integer port number and \fIhost\fR
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is either a domain-style name such as \fBwww.sunlabs.com\fR or
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a numerical IP address such as \fB127.0.0.1\fR.
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Use \fIlocalhost\fR to refer to the host on which the command is invoked.
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.PP
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The following options may also be present before \fIhost\fR
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to specify additional information about the connection:
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.TP
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\fB\-myaddr\fI addr\fR
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\fIAddr\fR gives the domain-style name or numerical IP address of
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the client-side network interface to use for the connection.
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This option may be useful if the client machine has multiple network
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interfaces. If the option is omitted then the client-side interface
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will be chosen by the system software.
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.TP
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\fB\-myport\fI port\fR
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\fIPort\fR specifies an integer port number to use for the client's
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side of the connection. If this option is omitted, the client's
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port number will be chosen at random by the system software.
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.TP
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\fB\-async\fR
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The \fB\-async\fR option will cause the client socket to be connected
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asynchronously. This means that the socket will be created immediately but
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may not yet be connected to the server, when the call to \fBsocket\fR
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returns. When a \fBgets\fR or \fBflush\fR is done on the socket before the
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connection attempt succeeds or fails, if the socket is in blocking mode, the
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operation will wait until the connection is completed or fails. If the
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socket is in nonblocking mode and a \fBgets\fR or \fBflush\fR is done on
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the socket before the connection attempt succeeds or fails, the operation
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returns immediately and \fBfblocked\fR on the socket returns 1.
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.SH "SERVER SOCKETS"
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.PP
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If the \fB\-server\fR option is specified then the new socket
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will be a server for the port given by \fIport\fR.
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Tcl will automatically accept connections to the given port.
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For each connection Tcl will create a new channel that may be used to
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communicate with the client. Tcl then invokes \fIcommand\fR
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with three additional arguments: the name of the new channel, the
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address, in network address notation, of the client's host, and
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the client's port number.
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.PP
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The following additional option may also be specified before \fIhost\fR:
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.TP
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\fB\-myaddr\fI addr\fR
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\fIAddr\fR gives the domain-style name or numerical IP address of
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the server-side network interface to use for the connection.
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This option may be useful if the server machine has multiple network
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interfaces. If the option is omitted then the server socket is bound
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to the special address INADDR_ANY so that it can accept connections from
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any interface.
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.PP
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Server channels cannot be used for input or output; their sole use is to
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accept new client connections. The channels created for each incoming
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client connection are opened for input and output. Closing the server
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channel shuts down the server so that no new connections will be
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accepted; however, existing connections will be unaffected.
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.PP
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Server sockets depend on the Tcl event mechanism to find out when
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new connections are opened. If the application doesn't enter the
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event loop, for example by invoking the \fBvwait\fR command or
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calling the C procedure \fBTcl_DoOneEvent\fR, then no connections
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will be accepted.
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.SH CONFIGURATION OPTIONS
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The \fBfconfigure\fR command can be used to query several readonly
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configuration options for socket channels:
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.TP
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\fB\-sockname\fR
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This option returns a list of three elements, the address, the host name
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and the port number for the socket. If the host name cannot be computed,
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the second element is identical to the address, the first element of the
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list.
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.TP
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\fB\-peername\fR
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This option is not supported by server sockets. For client and accepted
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sockets, this option returns a list of three elements; these are the
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address, the host name and the port to which the peer socket is connected
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or bound. If the host name cannot be computed, the second element of the
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list is identical to the address, its first element.
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.PP
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.SH "SEE ALSO"
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flush(n), open(n), read(n)
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.SH KEYWORDS
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bind, channel, connection, domain name, host, network address, socket, tcp
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