Basic Packet-Sniffer Construction from the Ground Up – This is a detailed whitepaper on how to constuct a working packet-sniffer in ansii C. Excellent work, very detailed, a “must-read” for everybody.
You can download it from the following link: https://packetstormsecurity.com/files/download/14414/Sniffer_construction.txt
Source: https://packetstormsecurity.com/files/14414/Sniffer_construction.txt.html