| IO::Socket - Object interface to socket communications |
IO::Socket - Object interface to socket communications
use IO::Socket;
IO::Socket provides an object interface to creating and using sockets. It
is built upon the the IO::Handle manpage interface and inherits all the methods defined
by the IO::Handle manpage.
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 the Socket manpage.
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
See the perlfunc manpage 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 the perlfunc manpage in attempt to make the interface more flexible. These are
accept([PKG])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 and return a list of two sockets created, or an
empty list on failure.
Additional methods that are provided are:
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.
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.
timeout([VAL])
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.
the Socket manpage, the IO::Handle manpage, the IO::Socket::INET manpage, the IO::Socket::UNIX manpage
Graham Barr. atmark() by Lincoln Stein. Currently maintained by the
Perl Porters. Please report all bugs to <perlbug@perl.org>.
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.
| IO::Socket - Object interface to socket communications |