The documentation on this is really, really bad! There's no explanation on how to start a server. No explanation on how this would work with CodeMirror.
All you really know is that it is used with socket.io. That you need to handle operations on the server by sending them to all the clients. And that's it.
How do you start the server?
How do you connect to the server?
How do you handle operations on the server?
How would you implement CodeMirror?