Unanswered question from
http://www.ruby-forum.org/bb/viewtopic.php?t=147:


Does anyone know a way to calculate a checksum of a TCP packet in ruby? 
I'm asking this 'cause I'm using the Ruby-Pcap module and I need to
verify if I'm getting errors-free TCP packets. 
I could implement it, but it's probably hard and I didn't want to make
something that it's already done (if it is...).