WebSockets is a key technology for real-time applications, providing persistent two-way communications that are more efficient than polling. 1. It is an HTML5 protocol, allowing clients and servers to send data to each other at any time; 2. When using it, the front-end establishes connections and listens to events through several lines of code, and the back-end needs to cooperate with a library that supports WebSocket; 3. Application scenarios include chat rooms, stock updates, online games, collaborative documents, etc.; 4. When using it, pay attention to the cross-domain, reconnection mechanism, and message formats unified into JSON and encryption protocol wss://.

Real-time applications are very common now, such as chat rooms, online collaboration tools, real-time data monitoring panels, etc. To implement these features, HTML5 WebSockets is a very practical technical choice. It provides a durable, bidirectional communication channel that is more efficient and responsive than traditional polling methods.

What are WebSockets?

WebSockets is a network communication protocol provided by HTML5, allowing a long-term connection between the client and the server to conduct two-way data transmission through this connection. Unlike HTTP request-response mode, once a WebSocket connection is established, both parties can send data at any time.

To give a simple example: the stock price you see on a web page is updated in real time, and it is likely that WebSocket is working. It does not require the browser to constantly request new data, but it pushes it directly when the server updates.

How to use WebSockets in a project?

To use WebSockets on the front end, you only need a few lines of code to establish the connection:

 const socket = new WebSocket('ws://example.com/socket');

You can then listen for connection opening, receiving messages, error handling, and connection closing events:

• socket.onopen : Triggered when the connection is successfully established.
• socket.onmessage : fired when a message is received from the server.
• socket.onerror : Triggered when an error occurs.
• socket.onclose : Triggered when the connection is closed.

Sending messages to the server is also very simple:

 socket.send('Hello Server!');

It should be noted that the server side also needs to support the WebSocket protocol. Common backend technologies such as Node.js (with ws library), Python websockets or Django Channels can be easily implemented.

Frequently Asked Questions and Precautions

Although WebSockets is powerful, there are some things that are easy to ignore in actual use:

• Cross-domain issues : WebSocket is also restricted by the same-origin policy, and requires the server to configure CORS or use a proxy to resolve it.
• Connection remains : The connection may be interrupted when the network is unstable. It is recommended to add a reconnection mechanism.
• Message format : It is recommended to use JSON format to pass data uniformly to facilitate front-end parsing.
• Security : Use the encrypted wss:// protocol to prevent man-in-the-middle attacks.

If your application is deployed on HTTPS, WebSocket must also use wss:// , otherwise the browser will block the connection.

Examples of practical application scenarios

In addition to the aforementioned live chat and stock market, WebSocket is also suitable for:

• Player status synchronization in online games
• Collaborative document editing (such as multiple people editing Google Docs at the same time)
• Real-time notification system (such as message push from social platforms)

This kind of scenario has one thing in common: data needs to flow quickly and continuously between clients and servers, and WebSocket just satisfies this.

Basically, that's not complicated to use, but it can indeed bring about an improvement in experience. As long as the front and back ends are coordinated, it is not difficult to achieve a true real-time function.

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