UDP DNS Packet Sniffing

Question

So I have used jNetPcap to sniff network packets in one of my projects. My question is how do I extract DNS query and response from UDP packets? jNetPcap is just a Java wrapper on libpcap, if that helps.

I know to etract DNS packets I need to look at port 53, is it the same for UDP?

I am using something like this currently and then processing the pcap packet:

Pcap pcap = Pcap.openLive(device.getName(), snaplen, flags, timeout, errbuf);
        if (pcap == null) {
            System.err.printf("Error while opening device for capture: " +
                errbuf.toString());
            return;
        }
        PcapBpfProgram program = new PcapBpfProgram();
    String expression = "udp dst port 53";
    int optimize = 0;         // 0 = false
    int netmask = 0xFFFFFF00; // 255.255.255.0
        if (pcap.compile(program, expression, optimize, netmask) != Pcap.OK) {
            System.err.println(pcap.getErr());
            return;
        }

        if (pcap.setFilter(program) != Pcap.OK) {
        System.err.println(pcap.getErr());
        return;     
    }       
    System.out.println("Filter set !!! : " + expression);

        // Receive packet from the loop
        PcapPacketHandler<String> jpacketHandler = packet_handler();

Any other filter suggestions?

Thanks.