Rob:

I did a search on www.google.com with the keywords <big>open source tcp/ip 8051</big> and found the following interesting links that pertain to the subject.

http://web51.hw-server.com/start.html

http://www.dunkels.com/adam/uip/links.html

http://www.bluewind.it/an002.html

http://www.sics.se/~adam/lwip/news-print.html

Good Luck
Michael Karas