Socket.IO and Express.js
Socket.IO (http://socket.io) is a library that provides the capability to establish two-way communication between a client and the server in real time. This two-way communication is driven by the WebSocket technology.
The WebSocket technology is available in most modern browsers, and the easiest way to conceptualize it is to imagine a constant connection between a browser and the server, as opposed to the traditional sporadic HTTP requests. Another difference between WebSocket and traditional HTTP requests is that the former is a two-way channel, meaning that the server can initiate the data transfer. This ...