Today I came across the Public Commander Keen Forum. They have a thread running (click here) about NetKeen; a reserve-engineering project of Commander Keen. The code also uses parts from Wolfenstein 3D and Doom. You can see the details in the link and you can download a copy here.

How does it look like in action?

The red Yorp shoots Keen.

On YouTube you can also find video's of NetKeen.

How to get it running?

1. Download DOSBox 0.74 and install it.
2. Download the neccesary NetKeen files (link).
3. Go to Start > Programs > DOSBox-0.74 > Options and open DOSBox 0.74 Options.
4. Scroll down to the bottom and set IPX to true and mount a C: drive (make it like the screenshot below)

5. Save the file.
6. Create a folder in C:\ and name it 'DOS' (you'll get C:\DOS).
7. Extract NetKeen into C:\DOS.
8. Start up DOSBox through the start menu.
9. In DOSBox you have to define a server and client as follows:
9 a. Server: IPXNET STARTSERVER
9 b. Client: IPXNET CONNECT <IP adress of server>
Check out this screenshot if things are unclear: DOSBox IPX.
Note: you can run DOSBox twice on your computer and test it with multiplayer. Just connect to ' IPXNET CONNECT LOCALHOST' or your own IP address.
10. Go to the NetKeen folder by writing 'CD NETKEEN' followed by 'CD GAME' (see this screenshot)
11. Start NetKeen (see their readme.txt for information!)
11 a. Server: NETKEEN -server -ext ck6 -nodes 2
11 b. Client: NETKEEN -ext ck6 -nodes 2
Note: You can vary settings, ck5 instead of ck6 or the numder of nodes (number of player).

Happy gaming!