#!/usr/bin/perl

use warnings;
use strict;
use IO::Socket;
use Socket;

# use port 7890 as default
my $port = shift || 7890;

my $socket = IO::Socket::INET->new(
   LocalPort    => $port,
   Type         => SOCK_STREAM,
   Reuse        => 1,
   Listen       => 10,
)
   or die "Couldn't create server: $@\n";

while (my $client = $socket->accept()) {
   my ($port, $iaddr) = unpack_sockaddr_in($client->peername());
   $client->send(inet_ntoa($iaddr));
   $client->close();
}