There was a fork of CSE2 that had online multiplayer functionality. It was at the point where it was functional, but it didn't get much development after that. In order to use it, you will need to host your own server. To do that with a computer at home, you'll need to set up port forwarding on your router. You could also rent a server using a service like Amazon's AWS or DigitalOcean, but you'll need to look into the setup/configuration process as well as the prices associated with running them. I should still have the necessary files around, if you're interested.