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.

perl v5.22.1                                       2020-10-19                                  IO::Socket(3perl)