I literally was going to do this this coming weekend, same name even!
I was going to take a much different approach however - I was going to use rabbitmq speaking STOMP over a websocket [0] with two queues, one for client moves, which the server would consume and write to the moves queue, which each client would consume. This would allow the server to do more fancy rate limiting / throttling as not to just lead to a message storm. This, along with storing the game state in a db, allows for scaling out app servers.
I never thought this little project would get this big!
If someone wants to help me scale this, or add things like chat, please do! Just send a PR on Github!
https://github.com/grant/hnplays2048