A WebSocket session between the client and server is built upon a standard TCP connection. Although the WebSocket protocol has its own control frames (mainly to create and sustain the connection) coded by the Internet Engineering Task Force in the RFC 6455 (http://tools.ietf.org/html/rfc6455), the peers are not obliged to use any specific format to exchange application data. You may use plaintext, XML, JSON, or anything else to transmit your data. As you probably remember, this is quite different from SOAP-based WebServices, which had bloated specifications of the exchange protocol. The same goes for RESTful architectures; we no longer have the predefined verb methods from HTTP (GET, PUT, POST, and DELETE), status codes, and the whole semantics of an HTTP request.

This liberty means that WebSockets are pretty low level compared to the technologies that we have used up to this point, but thanks to this, the communication overhead is minimal. The protocol is less verbose...