Programming Perl, 4th Edition

socketpair

socketpair SOCKET1, SOCKET2, DOMAIN, TYPE, PROTOCOL

This function creates an unnamed pair of sockets in the specified domain of the specified type. DOMAIN, TYPE, and PROTOCOL are specified the same as for socketpair(2). You will need to use Socket to get the required constants. If either socket argument is undefined, it will be autovivified. The function returns true if successful, and false otherwise. On a system where socketpair(2) is unimplemented, calling this function raises an exception.

This function is typically used just before a fork. One of the resulting processes should close SOCKET1, and the other should close SOCKET2. You can use these sockets bidirectionally, unlike the filehandles created by the pipe function. Some systems define pipe using socketpair, in which a call to pipe(Rdr, Wtr) is essentially:

use Socket;
socketpair(Rdr, Wtr, AF_UNIX, SOCK_STREAM, PF_UNSPEC);
shutdown(Rdr, 1);        # no more writing for reader
shutdown(Wtr, 0);        # no more reading for writer

Perl v5.8 and later will emulate socketpair using IP sockets to localhost if your system implements sockets ...