CoCoIO is based on the WizNet 5100s ethernet chip. This amazing device can manage 4 separate TCP or UDP network stacks all by itself, the host computer's only job is to feed these pipes.
Some applications can be written in basic! I'm describing a simple web browser in the blog section of this site. Major update coming soon.
Which is fun, but we need real software, and at least two talented guys have stepped up. Mike 'n6il' Furman is well on his way to drivewire over ethernet, and the mysterious 'strickyak' is writing the rest of the BSD socket (things like arp,dig,ping,dhcp,ntp,tftp). Try these links:
https://github.com/n6il/cocoio-dw
https://github.com/strickyak/frobio
https://github.com/rickulland/CoCo-www
Compatibility issues: We have identified two configurations that don’t work right now.
A CoCo3 with 86 GIME and 6309 CPU, running NitrOS9 6309 version. The workaround is NitrOS9 6809 – the hardware is fine, it’s some gremlin in the optimized code vs the not so optimized 86 GIME. News - it seems this only applies to old fashioned dynamic RAM. Newer static RAM upgrades like Boomerang and Triad don't seem to care.
A CoCo3 with a Pro-Tector3. The last, three chip version. Afraid the only workaround we have right now is remove the Pro-Tector, but we are waiting for a (backordered) faster GAL.