Been trying to learn about older networking protocols a bit, and figured that I would start with IPX/SPX. So I built two MS-DOS virtual machines in VirtualBox, and got IPX communications working (after much trial and error).
The idea being to get several old DOS games to run, link up to a multiplayer match, interact with each game window, and capture the traffic using Wireshark from the host machine. From this, I got Quake, Masters of Orion 2, and MechWarrior 2 to communicate back and forth. Doom, Doom2, Duke3d, Warcraft, and several others either buggered up under the VM or just couldn't see the other VM on the IPX network.
What did I discover? None of the working games used SPX. Not even Microsoft's NET DIAG used SPX. They all ran ONLY on top of IPX. I can't even find SPX examples or use-cases of SPX traffic running over IEEE 802.3 Ethernet II framing. I did find references that it was in abundant use on token ring, but that's it.
Yet any IPX-aware application that I've hunted down so far usually advertises itself as "IPX/SPX", which seems to be a bit of a misnomer, since it doesn't seem to use SPX.
So what was SPX used for? Any DOS applications out there that use it which will run under my VM setup?
Edit: I am aware that IPX is to SPX as IP is to TCP (layer 3 to layer 4), so I expected to see an SPX layer underneath the IPX layer in Wireshark when I ran my tests.