How to retrieve a dns message from a bytebuffer

[Periya.Data <per...@gm...>]

Hi,
    I have a bytebuffer of size 2048 bytes. Its initial bytes have some
custom data (upto 70th byte). From 71st byte, the DNS messages are there. I
think I know the length of the DNS message (I am not yet sure about this).

How do I get one message at a time from the bytebuffer?

 I am doing something like this:

        byte[] dns_msg_buf= new byte[1024];
        bb.get(dns_msg_buf, 71, caplen);   // bb is a byte buffer with
custom data and dns msgs. Caplen is the len.
        Message dns_msg = new Message(dns_msg_buf);
        System.out.println("Message size: " + dns_msg.numBytes());

dns_msg.numBytes => seems to be returning the size of the header only =
which is 12 bytes. Is there a way to find the total length of the message =
hdr + 4 message sections?

Thanks,
PD.