IO::Socket::INET(3perl) Perl Programmers Reference Guide IO::Socket::INET(3perl)

IO::Socket::INET - Object interface for AF_INET domain sockets

use IO::Socket::INET;

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

Creates an "IO::Socket::INET" object, which is a reference to a newly created symbol (see the "Symbol" package). "new" optionally takes arguments, these arguments are in key-value pairs.

In addition to the key-value pairs accepted by IO::Socket, "IO::Socket::INET" provides.

PeerAddr    Remote host address          <hostname>[:<port>]
PeerHost    Synonym for PeerAddr
PeerPort    Remote port or service       <service>[(<no>)] | <no>
LocalAddr   Local host bind address      hostname[:port]
LocalHost   Synonym for LocalAddr
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
ReuseAddr   Set SO_REUSEADDR before binding
Reuse       Set SO_REUSEADDR before binding (deprecated,
                                             prefer ReuseAddr)
ReusePort   Set SO_REUSEPORT before binding
Broadcast   Set SO_BROADCAST before binding
Timeout     Timeout value for various operations
MultiHomed  Try all addresses for multi-homed hosts
Blocking    Determine if connection will be blocking mode

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. If the "Listen" argument is given, but false, the queue size will be set to 5.

Although it is not illegal, the use of "MultiHomed" on a socket which is in non-blocking mode is of little use. This is because the first connect will never fail with a timeout as the connect call will not block.

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.

If "Blocking" is set to 0, the connection will be in nonblocking mode. If not specified it defaults to 1 (blocking mode).


$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('');
$sock = IO::Socket::INET->new(
                        PeerPort  => 9999,
                        PeerAddr  => inet_ntoa(INADDR_BROADCAST),
                        Proto     => 'udp',
                        LocalAddr => 'localhost',
                        Broadcast => 1 ) 
                    or die "Can't bind : $IO::Socket::errstr\n";

If the constructor fails it will return "undef" and set the $IO::Socket::errstr package variable to contain an error message.

$sock = IO::Socket::INET->new(...)
    or die "Cannot create socket - $IO::Socket::errstr\n";

For legacy reasons the error message is also set into the global $@ variable, and you may still find older code which looks here instead.

$sock = IO::Socket::INET->new(...)
    or die "Cannot create socket - $@\n";


Return the address part of the sockaddr structure for the socket
Return the port number that the socket is using on the local host
Return the address part of the sockaddr structure for the socket in a text form xx.xx.xx.xx
Return the address part of the sockaddr structure for the socket on the peer host
Return the port number for the socket on the peer host.
Return the address part of the sockaddr structure for the socket on the peer host in a text form xx.xx.xx.xx

Socket, IO::Socket

Graham Barr. Currently maintained by the Perl Porters. Please report all bugs at

Copyright (c) 1996-8 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.

2022-12-12 perl v5.36.0