The document discusses WebSocket and node.js for building real-time applications. It covers why WebSocket and node.js are useful, what WebSocket is as an HTML5 standard, how to use WebSocket on both the client-side and server-side with node.js libraries, and how the WebSocket protocol works by creating a TCP server, performing a handshake, and then handling ongoing communications. The document suggests WebSocket and node.js could be used together with additional protocols like STOMP, XMPP, or AMQP.