The Realtime Engine

Nice that they're going to write the connection part properly. I had to switch from socket.io to sockjs a long time ago because socket.io was just too flaky. The code was pretty ad-hoc with its state (mishmash of .reconnecting, .reconnected, .disconnected, etc. predicates), and clients would randomly get stuck in in-between states if they were on 3G etc.

Wise decision to extract out browsers and environmental dependencies into Engine.IO. Apart from decoupling concerns, both these libraries become simpler and can attract more contributors with relevant experience. Socket.IO can now focus on important features like JSON encoding / decoding, custom events, automatic reconnection with exponential backoff and multiplexing etc. It would have been nice to show some before and after code examples and stats on performance under websockets, long polling etc. scenarios.