You don't need a server, we offer our realtime collaborative stack as a service. We're cooking something up right now similar to TogetherJS, if you'd like a sneak peak drop me a email (in my profile).

If you want to build and host your own realtime application take a look at HAProxy (tcp mode in 1.4) for load balancing the incoming websocket connections to your application stack. There has been a lot of success using Node.js with engine.io, socket.io, or take a look at the meta Primus module.