Establishing Reliable Connections Using BroadcastChannel

To install all solutions, refer to Solutions Installation

Using BroadcastChannel, different tabs from the same origin can communicate with each other. Some operations need to be executed in one tab and broadcast to others.

Example use case: When establishing a WebSocket connection with a server, only one tab should maintain the communication. This requires coordination between multiple tabs to elect a master tab for connection establishment and message broadcasting.

This solution uses BroadcastChannel to implement:

A relatively reliable system
Dynamic updates of tab lists
Master node election
Event monitoring

Implementation Workflow

Tab Initialization: When a tab opens and connects to BroadcastChannel, it first broadcasts a message (with ID generated as current timestamp + random number).
Existing Tab Response: Existing tabs receive the broadcast and reply.
ID Collection: Upon receiving responses, add sender IDs to the ID list (friendChannelIdSet).
List Finalization: After 300ms, finalize the ID list (friendChannelIdSet) to determine existing tabs.
Master Election: Each tab determines if it can become the master node based on the ID list.
Master Responsibilities:
- Send regular heartbeat broadcasts
- Save ID list as _oldFrendChannelIdList
- Clear current ID list (friendChannelIdSet)
- Re-evaluate master status based on old list; step down if necessary
Heartbeat Handling: Tabs receiving master heartbeats will:
- Reply to heartbeat
- Save master's ID list as _oldFrendChannelIdList
- Clear current ID list
- Add master node to ID list
Response Processing: Tabs add received IDs to their friendChannelIdSet.
Master Election Request: Non-master tabs set a timeout after receiving heartbeats. If timeout occurs:
- Broadcast master election request
- Become master if no rejections received within timeframe
Election Responses: Tabs receiving election requests reply with rejection/acceptance based on their own ID priority.

Installation

npmyarnpnpm

shell

npm install @havue/bc-connect --save

shell

yarn add @havue/bc-connect

shell

pnpm install @havue/bc-connect

Usage

Import:

import { BroadcastChannelManager } from 'havue'
// or
import { BroadcastChannelManager } from '@havue/solutions'
// or
import { BroadcastChannelManager } from '@havue/bc-connect'

Examples

Try copying this page's URL and opening it in multiple tabs to observe communication.

其他标签页实例id 列表

当前标签页实例 id:

当前标签页实例类型:

发送消息:

目标实例id:

Click to view code

templatescriptstyle

vue

<template>
  <div class="brdCnl-box">
    <div class="left-box">
      <div class="title">其他标签页实例id 列表</div>
      <div class="friend-item" v-for="friend in friendList" :key="friend">{{ friend }}</div>
    </div>
    <div class="right-box">
      <div class="current-info">当前标签页实例 id: {{ currentBcId }}</div>
      <div class="current-info">当前标签页实例 类型: {{ currentBcNodeType }}</div>
      <div class="options-box">
        <div class="form-item"><span class="label">发送消息:</span><input v-model="message" /></div>
        <button class="borad-btn" @click="handleBroadMessage">广播</button>
        <div class="form-item"><span class="label">目标实例id:</span><input v-model="targetId" /></div>
        <button class="sigle-btn" @click="handleBroadOneMessage">单发</button>
      </div>
      <div class="message-box">
        <div class="message-item" v-for="message in recieveMessageList" :key="message.id">
          <div class="id">id:{{ message.id }}</div>
          <div class="data">data: {{ message.data }}</div>
        </div>
      </div>
    </div>
  </div>
</template>

<script setup lang="ts">
import type { BcConnectSendMessageType } from '@havue/bc-connect'
import { ref, onMounted, onBeforeUnmount } from 'vue'
// import { BroadcastChannelManager, BcConnectEventTypeEnum } from '@havue/bc-connect'
import { BroadcastChannelManager, BcConnectEventTypeEnum } from '@havue/solutions'

let bcManager: BroadcastChannelManager | null = null

const currentBcId = ref()
const currentBcNodeType = ref()

const friendList = ref<Array<number>>([])
const message = ref()
const targetId = ref()

const recieveMessageList = ref<Array<BcConnectSendMessageType>>([])

function handleBroadMessage() {
  if (!message.value) {
    alert('请输入消息')
    return
  }
  bcManager?.send('test-message', message.value)
}

function handleBroadOneMessage() {
  if (!message.value) {
    alert('请输入消息')
    return
  }
  if (!targetId.value) {
    alert('请输入目标id')
    return
  }
  bcManager?.sendToTarget('test-message', Number(targetId.value), message.value)
}

onMounted(() => {
  if (!bcManager) {
    bcManager = new BroadcastChannelManager('bc_test')
  }

  currentBcId.value = bcManager.id
  friendList.value = bcManager.friendList
  bcManager.connect()
  bcManager.on('test-message', (info) => {
    recieveMessageList.value.push(info)
  })
  bcManager.on(BcConnectEventTypeEnum.Friend_List_Update, (info) => {
    friendList.value = info.data || []
  })
  bcManager.on(BcConnectEventTypeEnum.Node_Type_Change, (info) => {
    currentBcNodeType.value = info.data
  })
})

onBeforeUnmount(() => {
  bcManager?.close()
  bcManager?.destroy()
  bcManager = null
})
</script>

scss

<style lang="scss" scoped>
.brdCnl-box {
  box-sizing: border-box;
  display: flex;
  width: 100%;
  height: 600px;
  color: black;
  background-color: #4d797c;

  .left-box {
    width: 30%;
    overflow: auto;

    .title {
      font-size: 18px;
      font-weight: bold;
    }

    .friend-item {
      padding: 6px 10px;
      margin: 5px;
      background-color: rgb(100 148 237);
    }
  }

  .right-box {
    display: flex;
    flex: 1;
    flex-direction: column;
    padding: 5px 10px;
    background-color: #4e7c4d;

    .current-info {
      padding: 3px 5px;
      background-color: #a8b9be;
    }

    .message-box {
      flex: 1;
      margin-top: 10px;
      overflow: auto;
      background-color: antiquewhite;

      .message-item {
        padding: 5px;
        margin: 5px;
        background-color: #8cbba9;

        .id {
          font-weight: bold;
        }

        .message {
          color: #44b15c;
        }
      }
    }

    .form-item {
      display: flex;
      align-items: center;
      margin: 5px 20px;

      .label {
        display: inline-block;
        width: 100px;
        text-align: right;
      }

      input {
        flex: 1;
        padding: 5px;
        font-size: 16px;
        color: #fff;
        background-color: black;
      }
    }

    button {
      width: 100%;
      color: black;
      background-color: #a8b9be;
    }
  }
}
</style>

Source Code

manager.ts

// #region typedefine
/** 事件数据类型 */
export type BcConnectSendMessageType = {
  /** 事件类型 */
  type: string
  /** 数据 */
  data: any
  /** 发送事件的实例id */
  id: number
  /** 消息是发送给目标实例id的 */
  targetId?: number
}

/** 事件类型 */
export enum BcConnectEventTypeEnum {
  /** 初始广播 */
  Broadcast = 'Hello world',
  /** 回复初始广播 */
  Broadcast_Reply = 'I can hear you',
  /** 主节点心跳 */
  Main_Node_Hearbeat = '苍天还在，别立黄天',
  /** 回复主节点心跳 */
  Res_Main_Node_Hearbeat = '苍天在上，受我一拜',
  /** 长时间未收到主节点心跳，我想当主节点，你们同意吗 */
  Req_Be_Main_Node = '苍天已死，黄天当立',
  /** 排资论辈，我应是主节点，不同意 */
  Res_Be_Main_Node = '我是黄天，尔等退下',
  /** 当前BC节点类型更改 */
  Node_Type_Change = 'node type change',
  /** 其他标签页BC节点id列表更新 */
  Friend_List_Update = 'friend list update'
}

/** 当前webview BroadcastChannel节点类型 */
export enum BcConnectNodeTypeEnum {
  Main = 'main',
  Normal = 'normal'
}
// #endregion typedefine

// 消息超时时间
const MessageTimeout = 300

/**
 * 使用BroadcastChannel与其他标签页进行通信
 */
export class BroadcastChannelManager {
  /** 通道名称 */
  private _bcName: string
  /** BroadcastChannel实例 */
  private _broadcastChannel: BroadcastChannel | undefined = undefined
  /** 事件map */
  private _eventMap: Map<string, Array<(_: BcConnectSendMessageType) => void>>
  /** 主节点发送心跳的interval */
  private _mainNodeMsgInterval: number | null = null
  /** 认为主节点掉线的timeout */
  private _mainNodeMsgTimeoutTimer: number | null = null
  /** 更新友方列表的timeout */
  private _updateFriendListTimer: number | null = null
  /** 当前实例id */
  public id: number = Date.now() + Math.random()
  /** 记录的友方id数组 */
  private _oldFrendChannelIdList: Array<number> = []
  /** 正在更新的右方id数组 */
  private _friendChannelIdSet: Set<number> = new Set()
  /** 当前节点类型 */
  private _nodeType: BcConnectNodeTypeEnum | undefined = undefined

  /** 是否开启调试模式，会在控制台打印相关信息 */
  private _debug: boolean = false

  constructor(name: string, debug: boolean = false) {
    this._debug = debug
    this._bcName = name
    this._eventMap = new Map()
    this._debug && console.log('BC:id:', this.id)
  }

  get nodeType() {
    return this._nodeType
  }

  get friendList() {
    return [...this._oldFrendChannelIdList]
  }

  public connect() {
    this._debug && console.log('BC:bc connect')
    this.close()
    this._broadcastChannel = new BroadcastChannel(this._bcName)
    this._bindBroadcastChannelEvent()
    this._updateFriendList()
  }

  public close() {
    this._debug && console.log('BC:bc close')
    this._broadcastChannel && this._broadcastChannel.close()
    this._broadcastChannel = undefined
    this._updateFriendListTimer && clearTimeout(this._updateFriendListTimer)
    this._updateFriendListTimer = null
    this._mainNodeMsgInterval && clearInterval(this._mainNodeMsgInterval)
    this._mainNodeMsgInterval = null
    this._mainNodeMsgTimeoutTimer && clearTimeout(this._mainNodeMsgTimeoutTimer)
    this._mainNodeMsgTimeoutTimer = null
    this._oldFrendChannelIdList = []
    this._friendChannelIdSet.clear()
    this._nodeType = undefined
  }

  /**
   * 切换节点类型
   * @param {BcConnectNodeTypeEnum} type
   * @returns
   */
  private _setNodeType(type: BcConnectNodeTypeEnum) {
    if (this._nodeType === type) {
      return
    }
    this._nodeType = type
    this.emit(BcConnectEventTypeEnum.Node_Type_Change, {
      type: BcConnectEventTypeEnum.Node_Type_Change,
      data: type,
      id: this.id
    })
  }

  /** 更新友方列表 */
  private _updateFriendList() {
    // 广播告知己方存在
    this.send(BcConnectEventTypeEnum.Broadcast)

    this._updateFriendListTimer && clearTimeout(this._updateFriendListTimer)

    this._updateFriendListTimer = setTimeout(() => {
      this._oldFrendChannelIdList = this._getNewFriendList()
      this._debug && console.log('BC:connect:updateFriendChannelIdList:', this._oldFrendChannelIdList)
      this.emit(BcConnectEventTypeEnum.Friend_List_Update, {
        type: BcConnectEventTypeEnum.Friend_List_Update,
        data: [...this._oldFrendChannelIdList],
        id: this.id
      })
      this._updataNodeType()
    }, MessageTimeout)
  }
  /** 绑定事件 */
  private _bindBroadcastChannelEvent() {
    this._broadcastChannel &&
      (this._broadcastChannel.onmessage = (event) => {
        const { type, targetId } = event.data
        if (targetId && targetId !== this.id) {
          return
        }
        this.emit(type, event.data)
      })

    // 收到世界呼唤
    this.on(BcConnectEventTypeEnum.Broadcast, (data) => {
      const { id } = data
      if (!this._friendChannelIdSet.has(id)) {
        this._friendChannelIdSet.add(id)
      }

      this.sendToTarget(BcConnectEventTypeEnum.Broadcast_Reply, id)
    })

    // 收到友方存在
    this.on(BcConnectEventTypeEnum.Broadcast_Reply, (data) => {
      const { id } = data
      this._addFriend(id)
    })

    // 收到其他申请为主节点
    this.on(BcConnectEventTypeEnum.Req_Be_Main_Node, (data) => {
      const { id } = data
      if (id > this.id) {
        this.sendToTarget(BcConnectEventTypeEnum.Res_Be_Main_Node, id)
      }
    })

    // 收到其他节点回复主节点心跳
    this.on(BcConnectEventTypeEnum.Res_Main_Node_Hearbeat, (data) => {
      this._addFriend(data.id)
    })

    this._bindNodeEvent()
  }

  /** 监听节点类型切换事件 */
  private _bindNodeEvent() {
    const onMainNodeHearbeat = (data: BcConnectSendMessageType) => {
      this._timeoutToBeMainNode()
      this._catchOldFriend()
      this._addFriend(data.id)
      this.send(BcConnectEventTypeEnum.Res_Main_Node_Hearbeat)
    }

    this.on(BcConnectEventTypeEnum.Node_Type_Change, (info) => {
      const { data } = info
      this._mainNodeMsgInterval && clearInterval(this._mainNodeMsgInterval)
      this._debug && console.log('BC:代理类型切换：', info.data)
      if (data === BcConnectNodeTypeEnum.Main) {
        // 定时发送主节点心跳
        this._mainNodeMsgInterval = setInterval(() => {
          this._catchOldFriend()
          this.send(BcConnectEventTypeEnum.Main_Node_Hearbeat)
        }, MessageTimeout)
      } else if (data === BcConnectNodeTypeEnum.Normal) {
        this._timeoutToBeMainNode()
      }
      // 收到主节点心跳, 重新更新友方列表
      this.on(BcConnectEventTypeEnum.Main_Node_Hearbeat, onMainNodeHearbeat)
    })
  }

  /** 获取最新的友方列表 */
  private _getNewFriendList() {
    return [...this._friendChannelIdSet].sort((a, b) => a - b)
  }
  /**
   * 更新当前节点类型
   */
  private _updataNodeType() {
    this._mainNodeMsgInterval && clearInterval(this._mainNodeMsgInterval)
    if (this._oldFrendChannelIdList.length === 0 || Math.min(...this._oldFrendChannelIdList) > this.id) {
      if (this._nodeType === BcConnectNodeTypeEnum.Main) {
        return
      }
      this._setNodeType(BcConnectNodeTypeEnum.Main)
    } else {
      if (this._nodeType === BcConnectNodeTypeEnum.Normal) {
        return
      }
      this._setNodeType(BcConnectNodeTypeEnum.Normal)
    }
  }

  private _timeoutToBeMainNode() {
    this._mainNodeMsgTimeoutTimer && clearTimeout(this._mainNodeMsgTimeoutTimer)
    // 超时未收到心跳，认为主节点掉线，申请为主节点
    this._mainNodeMsgTimeoutTimer = setTimeout(() => {
      this._req_beMainNode()
    }, MessageTimeout * 3)
  }

  /**
   * 保持记录的活跃的友方id列表
   * 清空正在记录的友方id列表
   */
  private _catchOldFriend() {
    const newFriendList = this._getNewFriendList()
    if (this._oldFrendChannelIdList.join() !== newFriendList.join()) {
      this._debug && console.log('BC:updateFriendChannelIdList:', newFriendList)
      this.emit(BcConnectEventTypeEnum.Friend_List_Update, {
        type: BcConnectEventTypeEnum.Friend_List_Update,
        data: [...newFriendList],
        id: this.id
      })
      this._oldFrendChannelIdList = [...newFriendList]
    }

    if (this._nodeType === BcConnectNodeTypeEnum.Main && Math.min(...this._oldFrendChannelIdList) < this.id) {
      // 有更小的id，不再为主节点
      this._setNodeType(BcConnectNodeTypeEnum.Normal)
    }

    this._friendChannelIdSet.clear()
  }

  /**
   * 申请成为主节点
   */
  private _req_beMainNode() {
    this._debug && console.log('BC:req_beMainNode')

    // 向所有id友方节点发送申请
    this.send(BcConnectEventTypeEnum.Req_Be_Main_Node)

    // 如果长时间未回复，认为自己可以当主节点
    const timer = setTimeout(() => {
      this._setNodeType(BcConnectNodeTypeEnum.Main)
    }, MessageTimeout)

    // 收到拒绝回复，清空timeout
    const handleRes_beMainNode = () => {
      clearTimeout(timer)
      this.off(BcConnectEventTypeEnum.Res_Be_Main_Node, handleRes_beMainNode)
    }

    this.on(BcConnectEventTypeEnum.Res_Be_Main_Node, handleRes_beMainNode)
  }

  /**
   * 添加友方
   * @param id 节点id
   */
  public _addFriend(id: number) {
    if (!this._friendChannelIdSet.has(id)) {
      this._friendChannelIdSet.add(id)
    }
  }

  /**
   * 广播消息
   * @param type 消息类型
   * @param data 数据
   */
  public send(type: string, data?: any) {
    this._broadcastChannel?.postMessage({
      type,
      data,
      id: this.id
    })
  }

  /**
   * 给特定id的节点发送消息
   * @param type 消息类型
   * @param targetId 目标节点id
   * @param data 数据
   */
  public sendToTarget(type: string, targetId: number, data?: any) {
    this._broadcastChannel?.postMessage({
      type,
      data,
      id: this.id,
      targetId
    })
  }

  /**
   * 注册事件
   * @param { string } event 事件类型
   * @param callback 回调
   * @returns void
   */
  public on(event: string, callback: (_: BcConnectSendMessageType) => void) {
    const callbacks = this._eventMap.get(event)
    if (!callbacks) {
      this._eventMap.set(event, [callback])
      return
    }

    if (callbacks.includes(callback)) {
      return
    }
    callbacks.push(callback)
  }

  /**
   * 注销事件
   * @param { string } event 事件类型
   * @param callback 事件回调
   * @returns
   */
  public off(event: string, callback?: (_: BcConnectSendMessageType) => void) {
    const callbacks = this._eventMap.get(event)
    if (!callbacks) {
      return
    }

    if (!callback) {
      callbacks.length = 0
      return
    }

    const index = callbacks.indexOf(callback)
    callbacks.splice(index, 1)
  }

  /**
   * 触发事件
   * @param { string } event 事件类型
   * @param data 数据
   */
  public emit(event: string, data: BcConnectSendMessageType) {
    const callbacks = this._eventMap.get(event) || []

    callbacks.forEach((cb) => {
      cb(data)
    })
  }

  /**
   * 销毁
   */
  public destroy() {
    this._bcName = ''
    this._eventMap.clear()
    this._broadcastChannel?.close()
    this._broadcastChannel = undefined
    this._oldFrendChannelIdList = []
    this._friendChannelIdSet.clear()
    this.id = -1
    this._nodeType = undefined

    this._mainNodeMsgInterval && clearInterval(this._mainNodeMsgInterval)
    this._mainNodeMsgInterval = null
    this._mainNodeMsgTimeoutTimer && clearInterval(this._mainNodeMsgTimeoutTimer)
    this._mainNodeMsgTimeoutTimer = null
    this._debug && console.log('BC:destroy')
  }
}

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BroadcastChannelManager Class Reference

Constructor

Property	Description	Parameter Type
constructor	Creates instance with channel name	`(name: string) => void`

Instance Properties

Property	Description	Type
id	Unique instance ID	`number`
nodeType	Current node type	`NodeTypeEnum \| null`
friendList	List of other tab IDs	`number[]`
connect	Establish channel connection	`() => void`
close	Close connection	`() => void`
destroy	Destroy instance	`() => void`
send	Broadcast message to all	`(type: string, data?:any) => void`
sendToTarget	Send message to specific ID	`(type: string, targetId: number, data?:any) => void`
on	Listen for events	`(event: string, callback: (_: SendMessageType) => void) => void`
off	Remove event listener	`(event: string, callback?: (_: SendMessageType) => void) => void`
emit	Trigger event	`(event: string, data: SendMessageType) => void`

Type Definitions

/** 事件数据类型 */
export type BcConnectSendMessageType = {
  /** 事件类型 */
  type: string
  /** 数据 */
  data: any
  /** 发送事件的实例id */
  id: number
  /** 消息是发送给目标实例id的 */
  targetId?: number
}

/** 事件类型 */
export enum BcConnectEventTypeEnum {
  /** 初始广播 */
  Broadcast = 'Hello world',
  /** 回复初始广播 */
  Broadcast_Reply = 'I can hear you',
  /** 主节点心跳 */
  Main_Node_Hearbeat = '苍天还在，别立黄天',
  /** 回复主节点心跳 */
  Res_Main_Node_Hearbeat = '苍天在上，受我一拜',
  /** 长时间未收到主节点心跳，我想当主节点，你们同意吗 */
  Req_Be_Main_Node = '苍天已死，黄天当立',
  /** 排资论辈，我应是主节点，不同意 */
  Res_Be_Main_Node = '我是黄天，尔等退下',
  /** 当前BC节点类型更改 */
  Node_Type_Change = 'node type change',
  /** 其他标签页BC节点id列表更新 */
  Friend_List_Update = 'friend list update'
}

/** 当前webview BroadcastChannel节点类型 */
export enum BcConnectNodeTypeEnum {
  Main = 'main',
  Normal = 'normal'
}

Establishing Reliable Connections Using BroadcastChannel ​

Implementation Workflow ​

Installation ​

Usage ​

Examples ​

BroadcastChannelManager Class Reference ​

Constructor ​

Instance Properties ​

Type Definitions ​

Establishing Reliable Connections Using BroadcastChannel

Implementation Workflow

Installation

Usage

Examples

BroadcastChannelManager Class Reference

Constructor

Instance Properties

Type Definitions