I've played around some with NetPacket::ICMP and such. What I think you'd need to do, to test that particular UDP port, would be to listen locally on the ICMP port (which is a protocol like UDP and TCP), and read any incoming packets that occur when you connect via UDP.

Anyway, this is as far as I got, it doesn't seem to get a ICMP packet type that makes any sense, though, anyone have an idea why?

#!/usr/bin/perl -w

use Data::Dumper;
use NetPacket::ICMP;
use IO::Socket;

my $icmps = IO::Socket::INET->new("LocalHost" => "192.168.1.2", 
                                  "Proto" => "icmp") 
    or die "Cant icmp listen ($!)"; 

print "boo\n";

my $udptest = IO::Socket::INET->new("PeerAddr" => "192.168.1.20", 
                                    "PeerPort" => "2222", 
                                    "Proto" => "udp", 
                                    "Timeout" => 20); 

$udptest->print("test"); 

my $y = $icmps->recv($buffer, 1024, 0); 
if($y)
{
    ($xport, $iaddr) = unpack_sockaddr_in($y);
    $remotehost = inet_ntoa($iaddr);
    print("peerhost $remotehost:$xport\n");
}

my $dec = NetPacket::ICMP->decode($buffer); 

print Dumper($dec);
[download]

Which outputs:

boo
peerhost 192.168.1.20:0
$VAR1 = bless( {
                 '_parent' => undef,
                 'data' => 'c
                             @À¨À¨E Àl@@öùÀ¨À¨®

                                               qtest',
                 'cksum' => 60,
                 'type' => 69,
                 '_frame' => 'EÀ<c
                                  @À¨À¨E Àl@@öùÀ¨À¨®

                                                    qtest',
                 'code' => 192
               }, 'NetPacket::ICMP' );
[download]

Where 69 is not any of the possible packet types listed in NetPacket::ICMP.. So, no clue whats going haywire..

C.