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WebSocket中心跳检测与断开重连机制详解

作者：hktk_wb

心跳检测是指在WebSocket连接过程中定时向服务端发送和接收心跳消息,来确定当前连接是否是正常状态的检测机制,断开重连是指在WebSocket不正常断开连接后,进行重新连接的策略,下面我们就来看看这二者的具体实现吧

心跳检测

在长时间WebSocket连接过程中，容易因为网络或其他原因导致WebSocket断开而没有触发ws.onclose事件，导致无法获取WebSocket连接失败的状态。

利用心跳检测可以预防这一问题。心跳检测是指在WebSocket连接过程中定时向服务端发送和接收心跳消息，来确定当前连接是否是正常状态的检测机制。

断开重连

断开重连是指在WebSocket不正常断开连接后，进行重新连接的策略。

在WebSocket连接断开后，立马进行重新连接。如果连接失败，则间隔一定时间后再尝试重连，直到连接成功或者达到最大重连次数。

消息订阅

在WebSocket使用过程中，可能会在不同的页面或逻辑中需要订阅全部或部分WebSocket消息，利用消息订阅可以让使用者在不同页面中订阅获取相关的消息信息。

代码实现

定义WebSocket内部参数

this.url = url //WebSocket连接地址
this.ws = null //WebSocket连接对象
this.heartEnabled = heartEnabled //是否开启心跳
this.heartInterval = 10000 //心跳间隔时间
this.heartTimeout = 5000 //心跳超时时间
this.lockReconnect = false //是否禁止重连
this.heartTimer = null //心跳定时器
this.serverTimer = null //服务器超时定时器
this.reconnectCount = 0 //重连次数
this.maxReconnectCount = 5 //最大重连次数
this.observers = [] //消息订阅者列表
this.waitingMessages = [] //待执行命令列表

实现WebSocket连接

  //WebSocket连接
  connect() {
    this.ws = new WebSocket(this.url)

    this.ws.onopen = () => {
      this.reconnectCount = 0 // 重置重连次数
      this.heartEnabled && this.start() // 开启心跳

      // 发送所有等待发送的信息
      const length = this.waitingMessages.length
      for (let i = 0; i < length; ++i) {
        const message = this.waitingMessages.shift()
        this.send(message)
      }
    }

    this.ws.onclose = (event) => {
      console.log('WebSocket closed:', event)
      this.reconnect() //这里可根据具体情况判定是否重新连接
    }

    this.ws.onerror = (error) => {
      console.log('WebSocket error:', error)
      this.reconnect()
    }

    this.ws.onmessage = (event) => {
      //收到心跳信息则重置心跳，收到其他信息则触发回调
      if (event.data === 'pong') {
        this.start()
      } else {
        this.observers.forEach((observer) => {
          //如需要，这里可根据observer的订阅type来判断是否回调
          observer.callback(event.data)
        })
      }
    }
  }

消息订阅及发送

  //发送信息
  send(message) {
    //发送信息时若WebSocket还未连接，则将信息放入待发送信息中等待连接成功后发送
    if (this.onReady() !== WebSocket.OPEN) {
      this.waitingMessages.push(message)
      return this
    }

    this.ws.send(message)
    return this
  }

  //订阅WebSocket信息
  onObserve(callback, type = 'all') {
    const observer = { type, callback }
    this.observers.push(observer)

    return observer
  }

  //取消订阅信息
  cancelObserve(cancelObserver) {
    this.observers.forEach((observer, index) => {
      if (cancelObserver === observer) {
        this.observers.splice(index, 1)
      }
    })
  }

  //WebSocket连接状态
  onReady() {
    return this.ws.readyState
  }

心跳检测

  //开启心跳
  start() {
    this.reset()

    this.heartTimer = setTimeout(() => {
      this.send('ping')

      //达到心跳超时时间还没有返回心跳信息，则认为连接断开，关闭WebSocket并重连
      this.serverTimer = setTimeout(() => {
        this.ws.close()
      }, this.heartTimeout)
    }, this.heartInterval)
  }

  //重置心跳定时器/服务超时定时器
  reset() {
    this.heartTimer && clearTimeout(this.heartTimer)

    this.serverTimer && clearTimeout(this.serverTimer)
  }

断开重连

  //重连
  reconnect() {
    // 设置lockReconnect变量避免重复连接
    if (this.lockReconnect || this.reconnectCount >= this.maxReconnectCount) return
    this.lockReconnect = true

    this.reconnectCount++ //重连次数+1

    setTimeout(() => {
      this.connect()
      this.lockReconnect = false
    }, 1000 * this.reconnectCount) //重连次数越多，延时越久
  }

完整代码 js

class SocketConnect {
  constructor(url = 'ws://127.0.0.1:8080', heartEnabled = true) {
    this.url = url //WebSocket连接地址
    this.ws = null //WebSocket连接对象
    this.heartEnabled = heartEnabled //是否开启心跳
    this.heartInterval = 10000 //心跳间隔时间
    this.heartTimeout = 5000 //心跳超时时间
    this.lockReconnect = false //是否禁止重连
    this.heartTimer = null //心跳定时器
    this.serverTimer = null //服务器超时定时器
    this.reconnectCount = 0 //重连次数
    this.maxReconnectCount = 5 //最大重连次数
    this.observers = [] //消息订阅者列表
    this.waitingMessages = [] //待执行命令列表

    this.connect()
  }

  //WebSocket连接
  connect() {
    this.ws = new WebSocket(this.url)

    this.ws.onopen = () => {
      this.reconnectCount = 0 // 重置重连次数
      this.heartEnabled && this.start() // 开启心跳

      // 发送所有等待发送的信息
      const length = this.waitingMessages.length
      for (let i = 0; i < length; ++i) {
        const message = this.waitingMessages.shift()
        this.send(message)
      }
    }

    this.ws.onclose = (event) => {
      console.log('WebSocket closed:', event)
      this.reconnect()
    }

    this.ws.onerror = (error) => {
      console.log('WebSocket error:', error)
      this.reconnect()
    }

    this.ws.onmessage = (event) => {
      //收到心跳信息则重置心跳，收到其他信息则触发回调
      if (event.data === 'pong') {
        this.start()
      } else {
        this.observers.forEach((observer) => {
          observer.callback(event.data)
        })
      }
    }
  }

  //发送信息
  send(message) {
    //发送信息时若WebSocket还未连接，则将信息放入待发送信息中等待连接成功后发送
    if (this.onReady() !== WebSocket.OPEN) {
      this.waitingMessages.push(message)
      return this
    }

    this.ws.send(message)
    return this
  }

  //订阅webSocket信息
  onObserve(callback, type = 'all') {
    const observer = { type, callback }
    this.observers.push(observer)

    return observer
  }

  //取消订阅信息
  cancelObserve(cancelObserver) {
    this.observers.forEach((observer, index) => {
      if (cancelObserver === observer) {
        this.observers.splice(index, 1)
      }
    })
  }

  //开启心跳
  start() {
    this.reset()

    this.heartTimer = setTimeout(() => {
      this.send('ping')

      //5秒钟还没有返回心跳信息，则认为连接断开，关闭WebSocket并重连
      this.serverTimer = setTimeout(() => {
        this.ws.close()
      }, this.heartTimeout)
    }, this.heartInterval)
  }

  //重置心跳定时器/服务超时定时器
  reset() {
    this.heartTimer && clearTimeout(this.heartTimer)

    this.serverTimer && clearTimeout(this.serverTimer)
  }

  //重连
  reconnect() {
    // 设置lockReconnect变量避免重复连接
    if (this.lockReconnect || this.reconnectCount >= this.maxReconnectCount) return
    this.lockReconnect = true

    this.reconnectCount++ //重连次数+1

    setTimeout(() => {
      this.connect()
      this.lockReconnect = false
    }, 1000 * this.reconnectCount) //重连次数越多，延时越久
  }

  //WebSocket连接状态
  onReady() {
    return this.ws.readyState
  }
}

export default SocketConnect

使用示例

// WebSocket连接
const url = 'ws://127.0.0.1:8080'
const ws = new SocketConnect(url)

// 消息订阅
const observer = ws.onObserve((data) => {
  console.log('data:', data)
})

// 取消订阅
ws.cancelObserve(observer)

// 发送消息
ws.send('hello world')

完整代码 ts

type ObserverType = {
  type: string
  callback: (event: MessageEvent) => void
}

type MessageDataType = object

class SocketConnect {
  private url: string
  private ws: WebSocket | undefined //WebSocket实例
  private heartEnabled: boolean //是否开启心跳
  private heartInterval = 10000 //心跳间隔时间
  private heartTimeout = 5000 //心跳超时时间
  private lockReconnect = false //是否禁止重连
  private heartTimer: NodeJS.Timeout | undefined //心跳定时器
  private serverTimer: NodeJS.Timeout | undefined //服务器超时定时器
  private reconnectCount = 0 //重连次数
  private maxReconnectCount = 5 //最大重连次数
  private observers: ObserverType[] = [] //消息订阅者列表
  private waitingMessages: string[] = [] //待执行命令列表

  constructor(url = 'ws://127.0.0.1:8080', heartEnabled = false) {
    this.url = url
    this.heartEnabled = heartEnabled

    this.connect()
  }

  //WebSocket连接
  connect() {
    this.ws = new WebSocket(this.url)

    this.ws.onopen = () => {
      this.reconnectCount = 0 // 重置重连次数
      this.heartEnabled && this.start() // 开启心跳

      // 发送所有等待发送的信息
      const length = this.waitingMessages.length
      for (let i = 0; i < length; ++i) {
        const message = this.waitingMessages.shift()
        this.send(message)
      }
    }

    this.ws.onclose = (event) => {
      console.log('WebSocket closed:', event)
      this.reconnect()
    }

    this.ws.onerror = (error) => {
      console.log('WebSocket error:', error)
      this.reconnect()
    }

    this.ws.onmessage = (event: MessageEvent) => {
      //收到心跳信息则重置心跳，收到其他信息则触发回调
      if (event.data === 'pong') {
        this.start()
      } else {
        this.observers.forEach((observer) => {
          observer.callback(event.data)
        })
      }
    }
  }

  //发送信息
  send(message?: string) {
    if (message) {
      //发送信息时若WebSocket还未连接，则将信息放入待发送信息中等待连接成功后发送
      if (this.onReady() !== WebSocket.OPEN) {
        this.waitingMessages.push(message)
        return this
      }

      this.ws && this.ws.send(message)
    }

    return this
  }

  //订阅WebSocket信息
  onObserve(callback: (data: MessageDataType) => void, type = 'all') {
    const observer = { type, callback }
    this.observers.push(observer)

    return observer
  }

  //取消订阅信息
  cancelObserve(cancelObserver: ObserverType) {
    this.observers.forEach((observer, index) => {
      if (cancelObserver === observer) {
        this.observers.splice(index, 1)
      }
    })
  }

  //开启心跳
  private start() {
    this.reset()

    this.heartTimer = setTimeout(() => {
      this.send('ping')

      //5秒钟还没有返回心跳信息，则认为连接断开，关闭WebSocket并重连
      this.serverTimer = setTimeout(() => {
        this.ws && this.ws.close()
      }, this.heartTimeout)
    }, this.heartInterval)
  }

  //重连
  private reconnect() {
    // 设置lockReconnect变量避免重复连接
    if (this.lockReconnect || this.reconnectCount >= this.maxReconnectCount) return
    this.lockReconnect = true

    this.reconnectCount++ //重连次数+1

    setTimeout(() => {
      this.connect()
      this.lockReconnect = false
    }, 1000 * this.reconnectCount) //重连次数越多，延时越久
  }

  // 重置心跳定时器/服务超时定时器
  private reset() {
    this.heartTimer && clearTimeout(this.heartTimer)

    this.serverTimer && clearTimeout(this.serverTimer)
  }

  // WebSocket连接状态
  onReady() {
    return this.ws && this.ws.readyState
  }
}

export default SocketConnect

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