perl function socketpair

The socketpair function in Perl creates a pair of connected sockets, which can be used for interprocess communication. The sockets returned by socketpair can be used with functions like send, recv, select, etc. Here's an example:

use Socket;

socketpair(my $sock1, my $sock2, AF_UNIX, SOCK_STREAM, PF_UNSPEC)
    or die "socketpair failed: $!";

# Send a message from sock1 to sock2
print $sock1 "Hello, world!\n";

# Receive a message on sock2
my $msg;
recv($sock2, $msg, 1024, 0);

print "Received message: $msg\n";

# Clean up
close($sock1);
close($sock2);

In this example, we create a pair of UNIX-domain sockets using socketpair. The first argument is a scalar variable that will hold the file descriptor for one of the sockets, and the second argument is a scalar variable that will hold the file descriptor for the other socket. The third argument is the address family (AF_UNIX in this case), the fourth argument is the socket type (SOCK_STREAM for a connection-oriented socket), and the fifth argument is the protocol (PF_UNSPEC to use the default protocol for the given socket type and address family).

Once the sockets are created, we can use them for interprocess communication. In this example, we send a message from sock1 to sock2 using print. We then receive the message on sock2 using recv. The third argument to recv is the maximum length of the message to receive, and the fourth argument is the receive flags (set to 0 in this case). Finally, we close both sockets using close.