$ perl -w rdt.pl 10.1.2.3 12345 abc
Name "main::proto" used only once: possible typo at rdt.pl line 15.

##</code><code>##

# tshark
Capturing on eth0
  0.000000 nnn.nnn.nnn.nnn -> 10.1.2.3     UDP Source port: 51531  Destination port: 12345