uIP for pico]OS
This is a uIP-based network stack for pico]OS. It is currently based on version 3.0 of contiki. Support for both IPv4 and ipV6 is included.
In addition to standard uIP stack library includes two socket layers ("native" and BSD sockets) to make programming easier. BSD socket layer contains only basic functionality but should enable writing programs that are compatible with other environments using sockets.
Library includes some device drivers. Enc28j60 is quite common chip, driver being used currently is written by Ivan A. Sergeev.
For systems with more ram & rom there is also picoos-lwip library.