I built kfchess.com (https://github.com/paladin8/kfchess), which might be a helpful reference. It's by no means amazing code (I hacked it together quickly in my spare time), but it uses https://github.com/socketio/socket.io for real-time client-server communication. It's a relatively simple library to build on top of.

As for the backend, I would recommend whatever you're most familiar with. It doesn't make that much of a difference and you'll be way more productive in a language you know.

Love the idea of a Shogi site by the way!