sub ListenOnUDP
{
    # Open a port
    my $hSocket = IO::Socket::INET->new(
      LocalPort=>$intListenPort, 
      Proto=>$strProtocol
    ) or die "Can't create UDP socket: $@";
    my ($datagram,$flags);

    while ($hSocket->recv($datagram,42,$flags)) {
        my $ripaddr = $hSocket->peerhost;
        my $rport = $hSocket->peerport;

        my $hResponseSocket = IO::Socket::INET->new(
            Proto=>$strProtocol,
            PeerHost=>$ripaddr,
            PeerPort=>$intSendPort
        );

        $hResponseSocket->send("PONG!");
        close($hResponseSocket);
        last;
    }
    close($hSocket);
}