#! perl -slw
use strict;
use IO::Socket;

my $lsn = IO::Socket::INET->new(
    Listen => 1, LocalPort => $ARGV[0]
) or die $^E;

while( my $client = $lsn->accept ) {
    close $client;
}

##</code><code>##

C:\test>lsn 1025
Only one usage of each socket address (protocol/network address/port) is normally permitted at C:\test\lsn.pl line 5.