CoCoIOr features the WizNet 5100s ethernet chip. This amazing device manages 4 separate TCP or UDP network stacks all by itself, the host computer's job is to feed those pipes. Works with CoCo 1, 2, or 3. Available with or without an 8k EEPROM, to be used as a boot ROM or other nonvolatile storage.
Some applications can be written in basic! I'm describing a simple web browser in the blog section of this site. Henry 'strickyak' Strickland has 'frobio', a remote boot server/thing loader, with things! On the side, a whole pile of OS9 network utilities (things like arp, dig, ping, dhcp, ntp, tftp). Plus the 'stricktime' viewer for fun.
There is a user manual online here. Something of a moving target, check the release date time to time. Also check our blog page for software links.