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IO::Socket(3pm)        Perl Programmers Reference Guide        IO::Socket(3pm)




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(3), IO::Handle(3), IO::Socket::INET(3), IO::Socket::UNIX(3)


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.



perl v5.24.0                      2016-02-05                   IO::Socket(3pm)

perl 5.24 - Generated Sun Nov 13 19:45:13 CST 2016
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