e.g.  tcpdump -ax udp and port 6060 will give you

09:16:16.864188 eth1 < clientmach.1182 > 172.16.0.3.6060: udp 5
                         4500 008c 0a7f 0000 8011 c224 c0a8 0102
                         ac10 0003 049e 17ac 0078 7312 2131 3132
                         006d 6179 7572 6e61 696b 0000 0000 0000
                         0000 0000 0000 0000 0000 0000 0000 0038
                         3032 3335 3137 3936 3830 3432 3133 3130
                         3430 3530 3830 3037 3037 3931 3632 3033
                         3030 3734 3137 3931 3133 0000 0000 0000
                         0000 0000 0000 0000 0000 0030 303a 3830
                         3a41 443a 3833 3a31 353a 3543


2. The application data starts from the 29th byte i.e. 2131 3132 onwards
   The authentication info is from the 36th byte of application data till
   where the zeroes start.
   e.g. in the above case,
   the authentication info is 38 3032 3335 3137 3936 ... 3931 3133 convert to
   ascii to get the equivalent authentication information.