Differences and connections between WebSocket protocol and HTTP protocol

Differences and connections between WebSocket protocol and HTTP protocol

Introduction:
With the popularity of the Internet, the demand for Web applications continues to increase. In order to achieve real-time interaction and Push function, new communication protocol WebSocket emerged at the historic moment. The traditional HTTP protocol is gradually replaced by WebSocket in this process. This article will focus on the differences and connections between the WebSocket protocol and the HTTP protocol, and give specific code examples.

1. Characteristics of HTTP protocol:
HTTP protocol is an application layer protocol, based on the request-response model. HTTP requests are stateless, that is, each request is independent and the server does not retain the client's state information. The client obtains data or completes an interaction by sending an HTTP request to the server. After the server receives the request, it returns the data by sending an HTTP response to the client. This mode is suitable for traditional web browsing, but it is inexperienced for real-time interaction and push functions.

2. Characteristics of the WebSocket protocol:

1. Real-time: WebSocket can achieve full-duplex communication and establish a persistent communication connection between the client and the server. Send data in both directions in real time, providing better real-time performance.
2. Low latency: Because WebSocket adopts a full-duplex communication method, compared with the HTTP request-response mode, it avoids the process of establishing connections and sending headers multiple times, saving a lot of communication delays.
3. Reliability: Because WebSocket uses long connections, it can maintain the connection status and can handle problems such as network interruptions and connection failures, ensuring reliable transmission of data.

3. The difference between WebSocket and HTTP:

1. The handshake process is different: In the HTTP protocol, the client sends a request to the server, and the server returns a response to the client , and then the connection is closed; in the WebSocket protocol, a special handshake process will be performed between the client and the server. After the connection is successfully established, the long connection state can be maintained.
2. The data transmission formats are different: the HTTP protocol uses plain text to transmit data, while the WebSocket protocol can choose to use plain text or binary format to transmit data, giving it more flexibility.
3. The connection retention time is different: the HTTP protocol is a request-the connection will be closed after the response, and there is no persistent connection feature; while the WebSocket protocol establishes a long connection, maintains a persistent connection for a period of time, and provides real-time Communication and push functionality.

4. The connection between WebSocket and HTTP:

1. WebSocket is based on the HTTP protocol: the handshake process of WebSocket uses the HTTP Upgrade header information to upgrade the HTTP protocol It is the WebSocket protocol, so WebSocket extends the HTTP protocol and inherits some of the characteristics of HTTP.
2. Sharing the same port: WebSocket and HTTP share the same port and communicate through port 80 or port 443, so WebSocket and HTTP services can be accessed through the same communication interface.

Code example:
The following is a simple code example that uses the WebSocket protocol to implement the real-time chat function.

// 服务端代码
const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });

wss.on('connection', function connection(ws) {
  ws.on('message', function incoming(message) {
    console.log('received: %s', message);
    // 对收到的消息进行处理
    ws.send('Hello, ' + message);
  });
  
  ws.send('连接成功！');
});

// 客户端代码
const socket = new WebSocket('ws://localhost:8080');

socket.onopen = function() {
  console.log('WebSocket连接成功！');
};

socket.onmessage = function(event) {
  console.log('消息：' + event.data);
};

socket.send('Hello Server!');

This example uses the ws library of Node.js to implement a simple WebSocket server and client. When the client sends a message to the server, the server processes the message and sends a response to the client. The client prints out the response from the server when it receives it. Through the WebSocket protocol, two-way communication and real-time push functions are realized.

Conclusion:
The WebSocket protocol and the HTTP protocol are very different in realizing real-time interaction and push functions. The WebSocket protocol has the characteristics of real-time, low latency and reliability, and is suitable for application scenarios with real-time interaction and push functions. The HTTP protocol is suitable for one-time request-response mode. But WebSocket is an extension based on the HTTP protocol, and the two are connected and complementary to each other.

References:

1. https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API
2. https://developer .mozilla.org/en-US/docs/Web/HTTP/Overview

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