Stevens' book is a standard and is very good. I also recommend "Linux Programming by Example" by Arnold Robbins and, for lots of good, practical examples, "Building Open Source Network Security Tools" by Mike D. Schiffman. Finally, you simply can't beat "Advanced Linux Programming" http://www.advancedlinuxprogramming.com/
for the price and ease of obtaining.
In the end, you are probably going to be mostly involved with packet capture and packet building libraries, so hopefully I can save you some time and suggest that you Google for resources on pcap and libnet.