FIRST REPOSITORY

[eos/hostdependOTHERS.git] / I386LINUX / util / I386LINUX / man / mann / socket.n

'\"
'\" 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.
'\"
'\" RCS: @(#) $Id: socket.n,v 1.7.2.2 2003/05/15 18:41:06 hobbs Exp $
'\" The definitions below are for supplemental macros used in Tcl/Tk
'\" manual entries.
'\"
'\" .AP type name in/out ?indent?
'\"     Start paragraph describing an argument to a library procedure.
'\"     type is type of argument (int, etc.), in/out is either "in", "out",
'\"     or "in/out" to describe whether procedure reads or modifies arg,
'\"     and indent is equivalent to second arg of .IP (shouldn't ever be
'\"     needed;  use .AS below instead)
'\"
'\" .AS ?type? ?name?
'\"     Give maximum sizes of arguments for setting tab stops.  Type and
'\"     name are examples of largest possible arguments that will be passed
'\"     to .AP later.  If args are omitted, default tab stops are used.
'\"
'\" .BS
'\"     Start box enclosure.  From here until next .BE, everything will be
'\"     enclosed in one large box.
'\"
'\" .BE
'\"     End of box enclosure.
'\"
'\" .CS
'\"     Begin code excerpt.
'\"
'\" .CE
'\"     End code excerpt.
'\"
'\" .VS ?version? ?br?
'\"     Begin vertical sidebar, for use in marking newly-changed parts
'\"     of man pages.  The first argument is ignored and used for recording
'\"     the version when the .VS was added, so that the sidebars can be
'\"     found and removed when they reach a certain age.  If another argument
'\"     is present, then a line break is forced before starting the sidebar.
'\"
'\" .VE
'\"     End of vertical sidebar.
'\"
'\" .DS
'\"     Begin an indented unfilled display.
'\"
'\" .DE
'\"     End of indented unfilled display.
'\"
'\" .SO
'\"     Start of list of standard options for a Tk widget.  The
'\"     options follow on successive lines, in four columns separated
'\"     by tabs.
'\"
'\" .SE
'\"     End of list of standard options for a Tk widget.
'\"
'\" .OP cmdName dbName dbClass
'\"     Start of description of a specific option.  cmdName gives the
'\"     option's name as specified in the class command, dbName gives
'\"     the option's name in the option database, and dbClass gives
'\"     the option's class in the option database.
'\"
'\" .UL arg1 arg2
'\"     Print arg1 underlined, then print arg2 normally.
'\"
'\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $
'\"
'\"     # Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
.if t .wh -1.3i ^B
.nr ^l \n(.l
.ad b
'\"     # Start an argument description
.de AP
.ie !"\\$4"" .TP \\$4
.el \{\
.   ie !"\\$2"" .TP \\n()Cu
.   el          .TP 15
.\}
.ta \\n()Au \\n()Bu
.ie !"\\$3"" \{\
\&\\$1  \\fI\\$2\\fP    (\\$3)
.\".b
.\}
.el \{\
.br
.ie !"\\$2"" \{\
\&\\$1  \\fI\\$2\\fP
.\}
.el \{\
\&\\fI\\$1\\fP
.\}
.\}
..
'\"     # define tabbing values for .AP
.de AS
.nr )A 10n
.if !"\\$1"" .nr )A \\w'\\$1'u+3n
.nr )B \\n()Au+15n
.\"
.if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n
.nr )C \\n()Bu+\\w'(in/out)'u+2n
..
.AS Tcl_Interp Tcl_CreateInterp in/out
'\"     # BS - start boxed text
'\"     # ^y = starting y location
'\"     # ^b = 1
.de BS
.br
.mk ^y
.nr ^b 1u
.if n .nf
.if n .ti 0
.if n \l'\\n(.lu\(ul'
.if n .fi
..
'\"     # BE - end boxed text (draw box now)
.de BE
.nf
.ti 0
.mk ^t
.ie n \l'\\n(^lu\(ul'
.el \{\
.\"     Draw four-sided box normally, but don't draw top of
.\"     box if the box started on an earlier page.
.ie !\\n(^b-1 \{\
\h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.el \}\
\h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.\}
.fi
.br
.nr ^b 0
..
'\"     # VS - start vertical sidebar
'\"     # ^Y = starting y location
'\"     # ^v = 1 (for troff;  for nroff this doesn't matter)
.de VS
.if !"\\$2"" .br
.mk ^Y
.ie n 'mc \s12\(br\s0
.el .nr ^v 1u
..
'\"     # VE - end of vertical sidebar
.de VE
.ie n 'mc
.el \{\
.ev 2
.nf
.ti 0
.mk ^t
\h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n'
.sp -1
.fi
.ev
.\}
.nr ^v 0
..
'\"     # Special macro to handle page bottom:  finish off current
'\"     # box/sidebar if in box/sidebar mode, then invoked standard
'\"     # page bottom macro.
.de ^B
.ev 2
'ti 0
'nf
.mk ^t
.if \\n(^b \{\
.\"     Draw three-sided box if this is the box's first page,
.\"     draw two sides but no top otherwise.
.ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
.el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
.\}
.if \\n(^v \{\
.nr ^x \\n(^tu+1v-\\n(^Yu
\kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c
.\}
.bp
'fi
.ev
.if \\n(^b \{\
.mk ^y
.nr ^b 2
.\}
.if \\n(^v \{\
.mk ^Y
.\}
..
'\"     # DS - begin display
.de DS
.RS
.nf
.sp
..
'\"     # DE - end display
.de DE
.fi
.RE
.sp
..
'\"     # SO - start of list of standard options
.de SO
.SH "STANDARD OPTIONS"
.LP
.nf
.ta 5.5c 11c
.ft B
..
'\"     # SE - end of list of standard options
.de SE
.fi
.ft R
.LP
See the \\fBoptions\\fR manual entry for details on the standard options.
..
'\"     # OP - start of full description for a single option
.de OP
.LP
.nf
.ta 4c
Command-Line Name:      \\fB\\$1\\fR
Database Name:  \\fB\\$2\\fR
Database Class: \\fB\\$3\\fR
.fi
.IP
..
'\"     # CS - begin code excerpt
.de CS
.RS
.nf
.ta .25i .5i .75i 1i
..
'\"     # CE - end code excerpt
.de CE
.fi
.RE
..
.de UL
\\$1\l'|0\(ul'\\$2
..
.TH socket n 8.0 Tcl "Tcl Built-In Commands"
.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;  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 \fBfconfigure\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.sunlabs.com\fR or
a numerical IP address such as \fB127.0.0.1\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
The \fB\-async\fR 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. 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.

.SH "SERVER SOCKETS"
.PP
If the \fB\-server\fR option is specified then the new socket
will be a server for the port given by \fIport\fR (either an integer
or a service name, where supported and understood by the host
operating system).
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
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 \fIhost\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 special address INADDR_ANY so that it can accept connections from
any interface.
.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 doesn't 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 my be retrieved from the created server socket using the
\fBfconfigure\fR command to retrieve the \fB\-sockname\fR option as
described below.

.SH "CONFIGURATION OPTIONS"
The \fBfconfigure\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.
.TP
\fB\-sockname\fR
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.
.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.
.PP

.SH "SEE ALSO"
fconfigure(n), flush(n), open(n), read(n)

.SH KEYWORDS
bind, channel, connection, domain name, host, network address, socket, tcp