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NAME

       IO::Socket - Object interface to socket communications

SYNOPSIS

           use IO::Socket;

DESCRIPTION

       "IO::Socket" provides an object interface to creating and using sockets. It is built upon
       the IO::Handle interface and inherits all the methods defined by IO::Handle.

       "IO::Socket" only defines methods for those operations which are common to all types of
       socket. Operations which are specified to a socket in a particular domain have methods
       defined in sub classes of "IO::Socket"

       "IO::Socket" will export all functions (and constants) defined by Socket.

CONSTRUCTOR

       new ( [ARGS] )
           Creates an "IO::Socket", which is a reference to a newly created symbol (see the
           "Symbol" package). "new" optionally takes arguments, these arguments are in key-value
           pairs.  "new" only looks for one key "Domain" which tells new which domain the socket
           will be in. All other arguments will be passed to the configuration method of the
           package for that domain, See below.

            NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE

           As of VERSION 1.18 all IO::Socket objects have autoflush turned on by default. This
           was not the case with earlier releases.

            NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE

METHODS

       See perlfunc for complete descriptions of each of the following supported "IO::Socket"
       methods, which are just front ends for the corresponding built-in functions:

           socket
           socketpair
           bind
           listen
           accept
           send
           recv
           peername (getpeername)
           sockname (getsockname)
           shutdown

       Some methods take slightly different arguments to those defined in perlfunc in attempt to
       make the interface more flexible. These are

       accept([PKG])
           perform the system call "accept" on the socket and return a new object. The new object
           will be created in the same class as the listen socket, unless "PKG" is specified.
           This object can be used to communicate with the client that was trying to connect.

           In a scalar context the new socket is returned, or undef upon failure. In a list
           context a two-element array is returned containing the new socket and the peer
           address; the list will be empty upon failure.

           The timeout in the [PKG] can be specified as zero to effect a "poll", but you
           shouldn't do that because a new IO::Select object will be created behind the scenes
           just to do the single poll.  This is horrendously inefficient.  Use rather true
           select() with a zero timeout on the handle, or non-blocking IO.

       socketpair(DOMAIN, TYPE, PROTOCOL)
           Call "socketpair" and return a list of two sockets created, or an empty list on
           failure.

       Additional methods that are provided are:

       atmark
           True if the socket is currently positioned at the urgent data mark, false otherwise.

               use IO::Socket;

               my $sock = IO::Socket::INET->new('some_server');
               $sock->read($data, 1024) until $sock->atmark;

           Note: this is a reasonably new addition to the family of socket functions, so all
           systems may not support this yet.  If it is unsupported by the system, an attempt to
           use this method will abort the program.

           The atmark() functionality is also exportable as sockatmark() function:

                   use IO::Socket 'sockatmark';

           This allows for a more traditional use of sockatmark() as a procedural socket
           function.  If your system does not support sockatmark(), the "use" declaration will
           fail at compile time.

       connected
           If the socket is in a connected state, the peer address is returned. If the socket is
           not in a connected state, undef is returned.

           Note that connected() considers a half-open TCP socket to be "in a connected state".
           Specifically, connected() does not distinguish between the ESTABLISHED and CLOSE-WAIT
           TCP states; it returns the peer address, rather than undef, in either case.  Thus, in
           general, connected() cannot be used to reliably learn whether the peer has initiated a
           graceful shutdown because in most cases (see below) the local TCP state machine
           remains in CLOSE-WAIT until the local application calls shutdown() or close(); only at
           that point does connected() return undef.

           The "in most cases" hedge is because local TCP state machine behavior may depend on
           the peer's socket options. In particular, if the peer socket has SO_LINGER enabled
           with a zero timeout, then the peer's close() will generate a RST segment, upon receipt
           of which the local TCP transitions immediately to CLOSED, and in that state,
           connected() will return undef.

       protocol
           Returns the numerical number for the protocol being used on the socket, if known. If
           the protocol is unknown, as with an AF_UNIX socket, zero is returned.

       sockdomain
           Returns the numerical number for the socket domain type. For example, for an AF_INET
           socket the value of &AF_INET will be returned.

       sockopt(OPT [, VAL])
           Unified method to both set and get options in the SOL_SOCKET level. If called with one
           argument then getsockopt is called, otherwise setsockopt is called.

       getsockopt(LEVEL, OPT)
           Get option associated with the socket. Other levels than SOL_SOCKET may be specified
           here.

       setsockopt(LEVEL, OPT, VAL)
           Set option associated with the socket. Other levels than SOL_SOCKET may be specified
           here.

       socktype
           Returns the numerical number for the socket type. For example, for a SOCK_STREAM
           socket the value of &SOCK_STREAM will be returned.

       timeout([VAL])
           Set or get the timeout value (in seconds) associated with this socket.  If called
           without any arguments then the current setting is returned. If called with an argument
           the current setting is changed and the previous value returned.

LIMITATIONS

       On some systems, for an IO::Socket object created with new_from_fd(), or created with
       accept() from such an object, the protocol(), sockdomain() and socktype() methods may
       return undef.

SEE ALSO

       Socket, IO::Handle, IO::Socket::INET, IO::Socket::UNIX

AUTHOR

       Graham Barr.  atmark() by Lincoln Stein.  Currently maintained by the Perl Porters.
       Please report all bugs to <perlbug@perl.org>.

COPYRIGHT

       Copyright (c) 1997-8 Graham Barr <gbarr@pobox.com>. All rights reserved.  This program is
       free software; you can redistribute it and/or modify it under the same terms as Perl
       itself.

       The atmark() implementation: Copyright 2001, Lincoln Stein <lstein@cshl.org>.  This module
       is distributed under the same terms as Perl itself.  Feel free to use, modify and
       redistribute it as long as you retain the correct attribution.