use Net::PcapUtils;
use NetPacket::IP;
use NetPacket::UDP;
use NetPacket::Ethernet qw/:types/;
use strict;

Net::PcapUtils::loop(
    sub {
        my ($arg, $header, $packet) = @_;
        my $ethernet = NetPacket::Ethernet->decode($packet);
        if ($ethernet->{'type'} == ETH_TYPE_IP) {
            my $ip = NetPacket::IP->decode($ethernet->{'data'}, $ethernet);
            my $udp = NetPacket::UDP->decode($ip->{'data'});

            .
            .

            print
                $ip->{'src_ip'}, ":", $udp->{'src_port'}, " -> ",
                $ip->{'dest_ip'}, ":", $udp->{'dest_port'}, "\n";
        }
    },
    'DEV'       =>  'eth0',
#    'FILTER'    =>  'udp dst host 192.168.1.1'
);