A million years ago I was an Atari ST user. I recall my roomie and I had a LAN between our computers, using the ST's MIDI interface. At the time, MIDI's 31kbps was blazing!

I just did some searching to see if I could find that software, but can't nail it down. I did find that hackers have taken it much farther. Apparently it's been developed to the point that you can do Ethernet, as referred to here: http://paradize.final-memory.org/sting1.shtml