Day24 [實作] 一對一視訊通話(4): 加入通話及掛斷機制

2021 iThome 鐵人賽

DAY 24

Modern Web

後疫情時代的 WebRTC 微學習系列第 24 篇

13th鐵人賽 webrtc

Nick Yu

2021-10-08 14:04:17

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結合前兩篇我們已經實現了 MVP（Minimum Viable Product；最小可行產品），完成了最簡單的一對一通話，後續我們會慢慢強化他的功能，今天我們會加上通話及掛斷機制，運作方法如下圖。

Server 訂閱掛斷電話

收到 leave 消息後向對方發送bye 對自己發送 leaved

// 離開房間
socket.on('leave', (room) => {
  socket.to(room).emit('bye')
  socket.emit('leaved')
})

Client 添加掛電話功能

index.html 中增加掛電話按鈕

<div>
  <button id="leaveBtn">Leave</button>
</div>

main.js 中增加掛斷電話

function hangup() {
  if (peerConn) {
    peerConn.close()
    peerConn = null
  }
}

main.js 中增加 bye 及 leaved 兩個訂閱

// 收到 leaved 把 socket 中斷連線
socket.on('leaved', (room, id) => {
  console.log('收到 leaved')
  // 中斷 socket
  socket.disconnect()
})

socket.on('bye', (room, id) => {
  console.log('收到 bye')
  // 對方要掛掉電話
  hunghp()
})

main.js 中增加按鈕綁定

const leaveBtn = document.querySelector('button#leaveBtn')

// 點擊後發送離開的訊息並掛斷電話
leaveBtn.onclick = () => {
  if (socket) {
    socket.emit('leave', room)
  }
  hangup()
}

Client 加入啟動通話的功能

index.html 中增加啟動通話按鈕

<div>
  <button id="startBtn">Start</button>
  <button id="leaveBtn">Leave</button>
</div>

把 socket.io 相關程式碼使用function 包起來

function connectIO() {
  // socket
  socket = io('ws://0.0.0.0:8080')

  socket.on('ready', async (msg) => {
    console.log(msg)

    // 發送 offer
    console.log('發送 offer ')
    await sendSDP(true)
  })

  socket.on('ice_candidate', async (data) => {
    console.log('收到 ice_candidate')

    const candidate = new RTCIceCandidate({
      sdpMLineIndex: data.label,
      candidate: data.candidate,
    })
    await peerConn.addIceCandidate(candidate)
  })

  socket.on('offer', async (desc) => {
    console.log('收到 offer')

    // 設定對方的配置
    await peerConn.setRemoteDescription(desc)

    // 發送 answer
    await sendSDP(false)
  })

  socket.on('answer', async (desc) => {
    console.log('收到 answer')

    // 設定對方的配置
    await peerConn.setRemoteDescription(desc)
  })

  socket.on('leaved', () => {
    console.log('收到 leaved')
    socket.disconnect()
  })

  socket.on('bye', () => {
    console.log('收到 bye')
    hangup()
  })

  socket.emit('join', room)
}

替換初始化方法

const startBtn = document.querySelector('button#startBtn')

...

// window.onload = init()
startBtn.onclick = init

加上按鈕控制

async function init() {
  await createStream()
  initPeerConnection()
  connectIO()
  startBtn.disabled = true
  leaveBtn.disabled = false
}

leaveBtn.onclick = () => {
  if (socket) {
    socket.emit('leave', room)
  }
  hangup()
  startBtn.disabled = false
  leaveBtn.disabled = true
}

完整程式碼：

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>1on1 webrtc</title>
  </head>
  <body>
    <div>
      <button id="startBtn">Start</button>
      <button id="leaveBtn">Leave</button>
    </div>

    <div>
      <video muted width="320" autoplay playsinline id="localVideo"></video>
      <video width="320" autoplay playsinline id="remoteVideo"></video>
    </div>

    <script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/4.0.1/socket.io.js"></script>
    <script src="https://webrtc.github.io/adapter/adapter-latest.js"></script>
    <script src="./js/main.js"></script>
  </body>
</html>

main.js

// video 標籤
const localVideo = document.querySelector('video#localVideo')
const remoteVideo = document.querySelector('video#remoteVideo')

// button 標籤
const startBtn = document.querySelector('button#startBtn')
const leaveBtn = document.querySelector('button#leaveBtn')

let localStream
let peerConn
let socket
const room = 'room1'

function connectIO() {
  // socket
  socket = io('ws://0.0.0.0:8080')

  socket.on('ready', async (msg) => {
    console.log(msg)
    // 發送 offer
    console.log('發送 offer ')
    await sendSDP(true)
  })

  socket.on('ice_candidate', async (data) => {
    console.log('收到 ice_candidate')
    const candidate = new RTCIceCandidate({
      sdpMLineIndex: data.label,
      candidate: data.candidate,
    })
    await peerConn.addIceCandidate(candidate)
  })

  socket.on('offer', async (desc) => {
    console.log('收到 offer')
    // 設定對方的配置
    await peerConn.setRemoteDescription(desc)

    // 發送 answer
    await sendSDP(false)
  })

  socket.on('answer', async (desc) => {
    console.log('收到 answer')

    // 設定對方的配置
    await peerConn.setRemoteDescription(desc)
  })

  socket.on('leaved', () => {
    console.log('收到 leaved')
    socket.disconnect()
    closeLocalMedia()
  })

  socket.on('bye', () => {
    console.log('收到 bye')
    hangup()
  })

  socket.emit('join', room)
}

/**
 * 取得本地串流
 */
async function createStream() {
  try {
    // 取得影音的Stream
    const stream = await navigator.mediaDevices.getUserMedia({
      audio: true,
      video: true,
    })

    // 提升作用域
    localStream = stream

    // 導入<video>
    localVideo.srcObject = stream
  } catch (err) {
    throw err
  }
}

/**
 * 初始化Peer連結
 */
function initPeerConnection() {
  const configuration = {
    iceServers: [
      {
        urls: 'stun:stun.l.google.com:19302',
      },
    ],
  }
  peerConn = new RTCPeerConnection(configuration)

  // 增加本地串流
  localStream.getTracks().forEach((track) => {
    peerConn.addTrack(track, localStream)
  })

  // 找尋到 ICE 候選位置後，送去 Server 與另一位配對
  peerConn.onicecandidate = (e) => {
    if (e.candidate) {
      console.log('發送 ICE')
      // 發送 ICE
      socket.emit('ice_candidate', room, {
        label: e.candidate.sdpMLineIndex,
        id: e.candidate.sdpMid,
        candidate: e.candidate.candidate,
      })
    }
  }

  // 監聽 ICE 連接狀態
  peerConn.oniceconnectionstatechange = (e) => {
    if (e.target.iceConnectionState === 'disconnected') {
      remoteVideo.srcObject = null
    }
  }

  // 監聽是否有流傳入，如果有的話就顯示影像
  peerConn.onaddstream = ({ stream }) => {
    // 接收流並顯示遠端視訊
    remoteVideo.srcObject = stream
  }
}

/**
 * 處理信令
 * @param {Boolean} isOffer 是 offer 還是 answer
 */
async function sendSDP(isOffer) {
  try {
    if (!peerConn) {
      initPeerConnection()
    }

    // 創建SDP信令
    const localSDP = await peerConn[isOffer ? 'createOffer' : 'createAnswer']({
      offerToReceiveAudio: true, // 是否傳送聲音流給對方
      offerToReceiveVideo: true, // 是否傳送影像流給對方
    })

    // 設定本地SDP信令
    await peerConn.setLocalDescription(localSDP)

    // 寄出SDP信令
    let e = isOffer ? 'offer' : 'answer'
    socket.emit(e, room, peerConn.localDescription)
  } catch (err) {
    throw err
  }
}

/**
 * 關閉自己的視訊
 */
function closeLocalMedia() {
  if (localStream && localStream.getTracks()) {
    localStream.getTracks().forEach((track) => {
      track.stop()
    })
  }
  localStream = null
}

/**
 * 掛掉電話
 */
function hangup() {
  if (peerConn) {
    peerConn.close()
    peerConn = null
  }
}

/**
 * 初始化
 */
async function init() {
  await createStream()
  initPeerConnection()
  connectIO()
  startBtn.disabled = true
  leaveBtn.disabled = false
}

// window.onload = init()

leaveBtn.onclick = () => {
  if (socket) {
    socket.emit('leave', room)
  }
  hangup()
  startBtn.disabled = false
  leaveBtn.disabled = true
}

startBtn.onclick = init