前端 WebSocket 实时通信实战：从原理到生产级封装

React 组件集成

在 React 中，需要特别注意资源清理，避免内存泄漏。使用 useRef 保存实例，并在 useEffect 的清理函数中调用 disconnect。

import React, { useEffect, useCallback, useRef, useState } from 'react';

function WebSocketComponent() {
  const [messages, setMessages] = useState([]);
  const [input, setInput] = useState('');
  const wsClientRef = useRef(null);

  useEffect(() => {
    wsClientRef.current = new WebSocketClient('ws://localhost:8080');
    wsClientRef.current.connect();

    wsClientRef.current.on('chat', (payload) => {
      setMessages(prev => [...prev, payload]);
    });

    return () => {
      if (wsClientRef.current) {
        wsClientRef.current.disconnect();
      }
    };
  }, []);

  const handleSend = useCallback(() => {
    if (input.trim() && wsClientRef.current) {
      wsClientRef.current.send({ 
        type: 'chat', 
        payload: { message: input, user: 'Current User' } 
      });
      setInput('');
    }
  }, [input]);

  return (
    <div>
      <div className="messages">
        {messages.map((message, index) => (
          <div key={index} className="message">
            <strong>{message.user}:</strong> {message.message}
          </div>
        ))}
      </div>
      <div className="input-area">
        <input 
          type="text" 
          value={input} 
          onChange={(e) => setInput(e.target.value)} 
          onKeyPress={(e) => e.key === 'Enter' && handleSend()} 
        />
        <button onClick={handleSend}>Send</button>
      </div>
    </div>
  );
}

export default WebSocketComponent;

进阶场景处理

认证与重试策略

生产环境通常需要鉴权，可以通过 URL 参数传递 Token。同时，引入指数退避算法能防止重连风暴。

class RetryWebSocketClient extends WebSocketClient {
  constructor(url, options = {}) {
    super(url);
    this.maxReconnectAttempts = options.maxReconnectAttempts || 10;
    this.reconnectDelay = options.reconnectDelay || 1000;
    this.exponentialBackoff = options.exponentialBackoff || true;
  }

  reconnect() {
    if (this.reconnectAttempts < this.maxReconnectAttempts) {
      this.reconnectAttempts++;
      const delay = this.exponentialBackoff 
        ? this.reconnectDelay * Math.pow(2, this.reconnectAttempts - 1) 
        : this.reconnectDelay;
      
      console.log(`Attempting to reconnect... (${this.reconnectAttempts}/${this.maxReconnectAttempts})`);
      setTimeout(() => {
        this.connect();
      }, delay);
    } else {
      console.error('Max reconnect attempts reached');
    }
  }
}

消息队列

当连接断开时，用户操作不应丢失。将消息暂存到队列，待连接恢复后批量发送。

class QueueWebSocketClient extends WebSocketClient {
  constructor(url) {
    super(url);
    this.messageQueue = [];
  }

  connect() {
    super.connect();
    this.socket.onopen = (event) => {
      console.log('WebSocket connected');
      this.connected = true;
      this.reconnectAttempts = 0;
      this.startHeartbeat();
      this.flushQueue();
    };
  }

  send(data) {
    if (this.connected) {
      this.socket.send(JSON.stringify(data));
    } else {
      this.messageQueue.push(data);
      console.log('WebSocket not connected, message queued');
    }
  }

  flushQueue() {
    if (this.connected && this.messageQueue.length > 0) {
      console.log(`Flushing ${this.messageQueue.length} queued messages`);
      this.messageQueue.forEach(message => {
        this.socket.send(JSON.stringify(message));
      });
      this.messageQueue = [];
    }
  }
}

服务端与管理器模式

Node.js 服务端示例

服务端需要维护在线用户集合，并处理广播与心跳响应。

const WebSocket = require('ws');
const server = new WebSocket.Server({ port: 8080 });
const clients = new Set();

server.on('connection', (socket) => {
  console.log('Client connected');
  clients.add(socket);

  socket.send(JSON.stringify({ type: 'system', payload: 'Welcome!' }));

  socket.on('message', (message) => {
    try {
      const parsedMessage = JSON.parse(message);
      
      if (parsedMessage.type === 'heartbeat') {
        socket.send(JSON.stringify({ type: 'heartbeat' }));
        return;
      }

      clients.forEach(client => {
        if (client.readyState === WebSocket.OPEN) {
          client.send(JSON.stringify(parsedMessage));
        }
      });
    } catch (error) {
      console.error('Error parsing message:', error);
    }
  });

  socket.on('close', () => {
    console.log('Client disconnected');
    clients.delete(socket);
  });
});

console.log('WebSocket server running on port 8080');

全局管理器

单例模式可以统一管理多个 WebSocket 连接，例如区分聊天频道和通知频道。

class WebSocketManager {
  static instance = null;
  constructor() {
    this.clients = {};
  }

  static getInstance() {
    if (!WebSocketManager.instance) {
      WebSocketManager.instance = new WebSocketManager();
    }
    return WebSocketManager.instance;
  }

  createClient(name, url, options = {}) {
    const client = new QueueWebSocketClient(url, options);
    this.clients[name] = client;
    client.connect();
    return client;
  }

  removeClient(name) {
    if (this.clients[name]) {
      this.clients[name].disconnect();
      delete this.clients[name];
    }
  }

  disconnectAll() {
    Object.values(this.clients).forEach(client => {
      client.disconnect();
    });
    this.clients = {};
  }
}

总结与建议

WebSocket 确实是实现实时通信的首选方案，但它并非万能药。在实际选型时，请遵循以下原则：

1. 按需使用：如果业务允许秒级延迟，轮询可能更简单可靠。
2. 稳定性优先：必须处理好断线重连、心跳保活和错误恢复。
3. 避免过度设计：简单的单聊场景不需要复杂的队列管理，根据复杂度权衡。

记住，技术是为业务服务的。如果你的 WebSocket 实现让系统变得更复杂或不可靠，那它就不是一个好的选择。