What is WebSocket and how does it differ from HTTP?

WebSocket is a network communication protocol that provides full-duplex communication capabilities over a single TCP connection. It is part of HTML5 and enables real-time, bidirectional interactive communication between servers and clients.

Main Differences from HTTP

1. Communication Mode

• HTTP: Half-duplex communication, client initiates request, server responds then connection closes
• WebSocket: Full-duplex communication, both parties can send and receive data simultaneously

2. Connection Persistence

• HTTP: Stateless protocol, each request requires establishing a new connection
• WebSocket: Persistent connection, can maintain long-term communication after establishment

3. Protocol Overhead

• HTTP: Each request includes complete HTTP headers, high overhead
• WebSocket: After connection establishment, data frame headers are very small (2-14 bytes), minimal overhead

4. Real-time Performance

• HTTP: Requires polling or long-polling for real-time communication, higher latency
• WebSocket: Server can actively push data, strong real-time capability

WebSocket Protocol Features

Handshake Process

WebSocket establishes connection through HTTP upgrade mechanism:

shell
Client Request:
GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Sec-WebSocket-Version: 13

Server Response:
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=

Data Frame Format

WebSocket uses lightweight data frame format, supporting both text and binary data transmission.

Application Scenarios

• Real-time chat applications
• Online gaming
• Stock market data streaming
• Collaborative editing
• Real-time monitoring and dashboards