Learning Node

Chapter 13. WebSockets and Socket.IO

In this chapter, we’re working in both the client and server environments, because both are necessary when it comes to WebSockets and Socket.IO.

WebSockets is a relatively new web technology that enables bidirectional, real-time communication directly from within a client to a server application, and back again. The communication occurs over TCP (Transmission Control Protocol), via sockets. The Socket.IO libraries provide the support necessary to implement this technology. Not only does Socket.IO provide a module to use in your Node application, but it also provides a client-side JavaScript library to enable the client end of the communication channel. For an added bonus, it also works as an Express middleware.

In this chapter I’ll introduce WebSockets more fully by demonstrating how Socket.IO works, both in the client and in the server.

WebSockets

Before jumping into using Socket.IO, I want to provide a quick overview of WebSockets. To do that, I also need to explain bidirectional full-duplex communication.

The term full duplex describes any form of data transmission that allows communication in both directions. The term bidirectional means that both endpoints of a transmission can communicate, as opposed to unidirectional communication, when one end of a data transmission is a sender and all other endpoints are receivers. WebSockets provides the capability for a web client, such as a browser, to open up bidirectional full-duplex communication ...