WebSockets Explained: Real-Time Data Without Polling

WebSockets are a technology that enables real-time, two-way communication between a web page and a server. Unlike traditional HTTP requests, which require the client to continually poll the server for updates, WebSockets establish a persistent connection that allows the server to push data to the client whenever it changes. This can greatly improve the user experience by reducing latency and conserving bandwidth.

However, WebSockets are not always the best solution. Before implementing them, it is important to consider several factors. First, each open WebSocket connection consumes server resources, so a large number of idle connections can be wasteful. Second, the network path between the client and server may not support long-lived connections, as some corporate proxies and older load balancers may drop or block them.

Third, when a WebSocket connection is lost, the client must handle the event and attempt to reconnect, as the browser does not automatically do so. Finally, security is a concern - WebSockets should always be used over a secure connection (wss) and the login credentials should be verified during the initial handshake, not in subsequent messages.

The article provides a practical example of a price ticker application using WebSockets. In this case, the server pushes price updates to the client every half second, allowing the dashboard to display the latest prices in real-time. The server is implemented using Node.js and the ws package, a popular WebSocket library for Node.

The client, written in JavaScript, connects to the WebSocket server, subscribes to the price updates, and logs each update as it arrives. The article demonstrates how to build a simple application using WebSockets, but cautions that they may not be the optimal choice for every use case.