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author | William Joye <wjoye@cfa.harvard.edu> | 2016-12-21 22:56:22 (GMT) |
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committer | William Joye <wjoye@cfa.harvard.edu> | 2016-12-21 22:56:22 (GMT) |
commit | d1a6de55efc90f190dee42ab8c4fa9070834e77d (patch) | |
tree | ec633f5608ef498bee52a5f42c12c49493ec8bf8 /tcl8.6/doc/socket.n | |
parent | 5514e37335c012cc70f5b9aee3cedfe3d57f583f (diff) | |
parent | 98acd3f494b28ddd8c345a2bb9311e41e2d56ddd (diff) | |
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Merge commit '98acd3f494b28ddd8c345a2bb9311e41e2d56ddd' as 'tcl8.6'
Diffstat (limited to 'tcl8.6/doc/socket.n')
-rw-r--r-- | tcl8.6/doc/socket.n | 235 |
1 files changed, 235 insertions, 0 deletions
diff --git a/tcl8.6/doc/socket.n b/tcl8.6/doc/socket.n new file mode 100644 index 0000000..3efdb37 --- /dev/null +++ b/tcl8.6/doc/socket.n @@ -0,0 +1,235 @@ +'\" +'\" 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: |