Little Perl program that dumps the data from UDP packets stored in a pcap file and write it to another file. Uses Net::Pcap

extractUDPDataFromPcapFile.pl

#!/usr/bin/perl

use strict;
use warnings;


use Net::Pcap;
use NetPacket::Ethernet qw(:types);
use NetPacket::IP qw(:protos);
use NetPacket::UDP;
use NetPacket::TCP;

my $err;
my $pcapFile =  $ARGV[0];
my $outFile = $ARGV[1];
open(my $fh, '>', $outFile) or die "Could not open file '$outFile' $!";

my $maxpkts=0;
my $pcap = Net::Pcap::open_offline($pcapFile, \$err) or die "Can't read '$pcapFile': $err\n";


Net::Pcap::loop($pcap, $maxpkts, \&process_packet, '');
Net::Pcap::close($pcap);
close $fh;

sub process_packet() {
        my ($user_data, $header, $packet) = @_;
        my $ip = NetPacket::IP->decode(NetPacket::Ethernet::strip($packet));
        if ($ip -> {proto} == IP_PROTO_UDP) {
                my $udp = NetPacket::UDP -> decode($ip -> {data});
                print $fh "$udp->{data} \n";
        }
}