I took the server down a while back because it kept causing 100% CPU usage for some reason. Never managed to figure out the problem.
However, since it's been so long I've just gone and updated all the software on the server (Ubuntu, NodeJS and Showdown itself) and started the server.
I'll leave it up for a little while and keep an eye on the server load. If there are 2 people around who can go on there at the same time and start a random battle that would be great. That's what was causing the issues before.
Server is at http://pokemondatabase.psim.us
UPDATE: had a battle on the server and it all seems to work fine, no overloading the CPU. So the server is back online (hopefully) permanently!