Socket.io adds rooms/namespaces as a feature, automatically reconnects with effort to not have all clients reconnect at the same time, covers compatibility edge

Socket.io adds rooms/namespaces as a feature, automatically reconnects with effort to not have all clients reconnect at the same time, covers compatibility edgecases, heartbeat, timeouts, custom events, multiple transport methods, server side implementations in multiple languages, supports non-ws fallback for reasons that might not be browser compatibility, and a good API.