Basic chat Applications with Socket IO

Lesson Title: Introduction to Socket IO

Objective: By the end of this lesson, students will understand the basics of Socket IO and its significance in real-time web applications.

Socket IO is an open-source, cross-platform library that provides full-duplex bidirectional communication between a client and a server based on events. It is built on the WebSocket protocol, providing additional capabilities such as automatic reconnection and fallback to HTTP long polling where WebSockets cannot be used.

Automatic reconnection​

Under some particular conditions, the WebSocket connection between the server and the client can be interrupted with both sides being unaware of the broken state of the link.

That’s why Socket IO includes a heartbeat mechanism, which periodically checks the status of the connection.

And when the client eventually gets disconnected, it automatically reconnects with an exponential back-off delay, in order not to overwhelm the server.

Packet buffering​

The packets are automatically buffered when the client is disconnected, and will be sent upon reconnection.

More information

How it works

The bidirectional channel between the Socket IO server (Node js) and the Socket IO client (browser, Node js, or another programming language) is established with a WebSocket connection whenever possible, and will use HTTP long-polling as fallback.

Materials:

– A computer with Node.js installed

– Internet access

– Code editor (e.g., Visual Studio Code)

– Node js

– Javascript