In the early 2000s, when I switched to the Mac from Windows (oh how times change), SubEthaEdit was an amazing leap in text editing. It allowed you to connect with other Macs to collaborate on the same document -- something we take for granted these days.
Here is Dominik Wagner, one of the original authors and now maintainer of SubEthaEdit, on the inception of this particular feature:
Luckily one of us dug up an old Xerox Parc Paper that showed how latency free live collaboration can be done. At that time it fit perfectly with the newly released Bonjour technology to allow for networking without configuration between Macs. That was super exciting and we quickly got to a point where we could see this technology as viable and so we went on to build our application.
The latest version of SubEthaEdit is free and open source. It brings back a lot of memories seeing this.