Perl in a Nutshell, 2nd Edition

Server-Side Sockets

On the server side, IO::Socket provides a nice wrapper for creating server sockets. The wrapper encompasses the socket, bind, and listen procedures, while creating a new IO::Socket object. For example, we can create an Internet-domain socket with IO::Socket::INET:

use IO::Socket;
$sock = new IO::Socket::INET (LocalAddr => 'maude.ora.com',
                              LocalPort => 8888,
                              Proto     => 'tcp',
                              Listen    => 5);
die "$!" unless $sock;

The parameters for the new socket object determine whether it is a server or a client socket. Because we’re creating a server socket, LocalAddr and LocalPort provide the address and port to bind to the socket. The Listen parameter gives the queue size for the number of client requests that can wait for an accept at any one time.

When the server receives a client request, it calls the accept method on the socket object. This creates a new socket object on which the rest of the communication can take place:

$new_sock = $sock->accept(  );

When communication is finished on both client and server sockets, they should be destroyed with close. If a socket is not properly closed, the next time you attempt to use a socket with the same name, the system will complain that the socket is already in use.