my $hSocket = IO::Socket::INET->new(
      LocalPort=>$intListenPort, 
      Proto=>$strProtocol
      ) or die "Can't create UDP socket: $@";
    ioctl($hSocket, 0x8004667e, pack("I", 1));
    my ($datagram,$flags);
    # Wait for a datagram, then open a response port,
      respond, then close both ports.
    while ($hSocket->recv($datagram,42,$flags)) {
...