Probably the finest computer game ever produced. You can grab a copy here.

https://palfrepedia.palfreman.com/downloads/NETKEEN-2013-03-26.zip

This is a multiplayer version of all Commander Keen episodes using the Keen4 game engine. It uses IPX networking inside DosBox. If you need a tunnel broker you can use netkeen.palfreman.com on port 8888.