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 Handle interface and inherits all the methods defined by 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 the Socket manpage.


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.

IO::Sockets will be in autoflush mode after creation. Note that versions of IO::Socket prior to 1.1603 (as shipped with Perl 5.004_04) did not do this. So if you need backward compatibility, you should set autoflush explicitly.


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:

    peername (getpeername)
    sockname (getsockname)

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


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 an array context a two-element array is returned containing the new socket and the peer address, the list will be empty upon failure.

Additional methods that are provided are


Set or get the timeout value 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.

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.


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


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


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.



IO::Socket::INET provides a constructor to create an AF_INET domain socket and some related methods. The constructor can take the following options

    PeerAddr    Remote host address          <hostname>[:<port>]
    PeerPort    Remote port or service       <service>[(<no>)] | <no>
    LocalAddr   Local host bind address      hostname[:port]
    LocalPort   Local host bind port         <service>[(<no>)] | <no>
    Proto       Protocol name (or number)    "tcp" | "udp" | ...
    Type        Socket type                  SOCK_STREAM | SOCK_DGRAM | ...
    Listen      Queue size for listen
    Reuse       Set SO_REUSEADDR before binding
    Timeout     Timeout value for various operations

If Listen is defined then a listen socket is created, else if the socket type, which is derived from the protocol, is SOCK_STREAM then connect() is called.

The PeerAddr can be a hostname or the IP-address on the ``xx.xx.xx.xx'' form. The PeerPort can be a number or a symbolic service name. The service name might be followed by a number in parenthesis which is used if the service is not known by the system. The PeerPort specification can also be embedded in the PeerAddr by preceding it with a ``:''.

If Proto is not given and you specify a symbolic PeerPort port, then the constructor will try to derive Proto from the service name. As a last resort Proto ``tcp'' is assumed. The Type parameter will be deduced from Proto if not specified.

If the constructor is only passed a single argument, it is assumed to be a PeerAddr specification.


   $sock = IO::Socket::INET->new(PeerAddr => '',
                                 PeerPort => 'http(80)',
                                 Proto    => 'tcp');

   $sock = IO::Socket::INET->new(PeerAddr => 'localhost:smtp(25)');

   $sock = IO::Socket::INET->new(Listen    => 5,
                                 LocalAddr => 'localhost',
                                 LocalPort => 9000,
                                 Proto     => 'tcp');

   $sock = IO::Socket::INET->new('');


sockaddr ()

Return the address part of the sockaddr structure for the socket

sockport ()

Return the port number that the socket is using on the local host

sockhost ()

Return the address part of the sockaddr structure for the socket in a text form xx.xx.xx.xx

peeraddr ()

Return the address part of the sockaddr structure for the socket on the peer host

peerport ()

Return the port number for the socket on the peer host.

peerhost ()

Return the address part of the sockaddr structure for the socket on the peer host in a text form xx.xx.xx.xx


IO::Socket::UNIX provides a constructor to create an AF_UNIX domain socket and some related methods. The constructor can take the following options

    Type        Type of socket (eg SOCK_STREAM or SOCK_DGRAM)
    Local       Path to local fifo
    Peer        Path to peer fifo
    Listen      Create a listen socket



Returns the pathname to the fifo at the local end


Returns the pathanme to the fifo at the peer end


the Socket manpage, Handle


Graham Barr <>


Copyright (c) 1996 Graham Barr. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.


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