序言

在山大会议中，我们不仅要实现多人视频会议，我们还需要实现一个类似 QQ、微信这样的即时通讯服务。在这个一对一的私人聊天服务中，我们添加了一个一对一的私人视频通话功能，一来是增加软件功能的多样性，二来也是为实现多人聊天做铺垫，先熟悉 WebRTC 在实际环境下的运行。

逻辑设计

首先，我们需要对私人视频通话的代码逻辑进行设计。我们之前在【山大会议】WebRTC基础之对等体连接这篇文章中介绍过基本的 WebRTC 对等体连接的过程。它的建立本质上是一个两次握手的过程：

发起方向接收方发送 OFFER 请求，并携带上自己的 SessionDescriptionProtocol （以后简写为 sdp）；
接收方接到发送方的 sdp ，创建 ANSWER ，生成 sdp 返回给发送方；
发送方接到接收方的 sdp 后，建立起 WebRTC 对等体连接。

在私人视频聊天模块中，我们决定采用去中心化的、P2P的架构设计，中心服务器仅做信令转发功能，由此可以绕过服务器本身带宽不足，难以支撑起高分辨率画面的问题。
其次，由于我们加入了会话加密功能，发起方可以选择本次通话是否需要加密，而接收方则需要知道对方是否开启了加密，以提示用户是否进行加密对话。
由于我们的服务器没有 SSL 证书，服务器与客户端发送的数据均是明文，这意味着我们无法在不可信信道上传递密钥。因此，我们采用了一种协商算法来生成一次性的密钥，而协商的过程也需要一次握手。最终，我们将过程简化，得到了最终的连接建立过程的逻辑流程：

为了描述的方便起见，我们将 主动方 称为 A ，被动方 称为 B 。

A 向 B 发起会话请求，其中携带密钥协商所需要的一些信息；
B 接到 A 的请求，根据携带的 协商信息 判断 A 是否开启加密，并作出回复，如果同意进行会话且 A 启用了加密，则继续根据 协商信息 计算得到公钥与私钥，将公钥发回给 A；
A 接到应答消息后，判断 B 是否同意会话，如果同意则生成 OFFER 请求，携带 sdp 发送给 B ，如果开启了加密，则获取 B 发回的公钥，通过算法得出私钥；
B 接到 OFFER 请求与 sdp，将 sdp 保存为 远程描述符 ，并创建 ANSWER 请求得到 本地描述符 ，并将其发送回 A；
A 接到 ANSWER ，将其中的 sdp 保存为 远程描述符 ，双方分别添加 Ice候选者 ，建立起对等体连接。

私人 WebRTC 工具类代码

// ChatRTC.tsx
import {AlertOutlined,CheckOutlined,CloseOutlined,ExclamationCircleOutlined,
} from '@ant-design/icons';
import Modal from 'antd/lib/modal';
import { globalMessage } from 'Components/GlobalMessage/GlobalMessage';
import { EventEmitter } from 'events';
import React from 'react';
import { ChatSocket } from 'Utils/ChatSocket/ChatSocket';
import {CALL_STATUS_ANSWERING,CALL_STATUS_CALLING,CALL_STATUS_FREE,CALL_STATUS_OFFERING,ChatWebSocketType,DEVICE_TYPE,PRIVATE_WEBRTC_ANSWER_TYPE,receiverCodecs,senderCodecs,
} from 'Utils/Constraints';
import eventBus from 'Utils/EventBus/EventBus';
import { getDeviceStream, getMainContent } from 'Utils/Global';
import { AUDIO_TYPE, buildPropmt } from 'Utils/Prompt/Prompt';
import { setCallStatus, setNowChattingId, setNowWebrtcFriendId } from 'Utils/Store/actions';
import store from 'Utils/Store/store';
import { eWindow } from 'Utils/Types';
import { setupReceiverTransform, setupSenderTransform } from 'Utils/WebRTC/RtcEncrypt';interface ChatRtcProps {socket: ChatSocket;myId: number;
}export class ChatRTC extends EventEmitter {callAudioPrompt: (() => void)[];answerAudioPrompt: (() => void)[];socket: ChatSocket;myId: number;localStream: null | MediaStream;remoteStream: null | MediaStream;sender?: number;receiver?: number;peer!: RTCPeerConnection;answerModal!: null | {destroy: () => void;};offerModal!: null | {destroy: () => void;};candidateQueue: Array<any>;useSecurity: boolean;security: string;constructor(props: ChatRtcProps) {super();this.callAudioPrompt = buildPropmt(AUDIO_TYPE.WEBRTC_CALLING, true);this.answerAudioPrompt = buildPropmt(AUDIO_TYPE.WEBRTC_ANSWERING, true);this.socket = props.socket;this.myId = props.myId;this.localStream = null;this.remoteStream = null;this.useSecurity = false;this.security = '[]';this.candidateQueue = new Array();this.socket.on('ON_PRIVATE_WEBRTC_REQUEST', (msg) => {this.responseCall(msg);});this.socket.on('ON_PRIVATE_WEBRTC_RESPONSE', ({ accept, sender, receiver, security }) => {if (sender === this.sender && receiver === this.receiver) {this.callAudioPrompt[1]();if (this.offerModal) {this.offerModal.destroy();this.offerModal = null;}if (accept === PRIVATE_WEBRTC_ANSWER_TYPE.ACCEPT) {this.createOffer(security);} else {switch (accept) {case PRIVATE_WEBRTC_ANSWER_TYPE.BUSY:globalMessage.error({content: '对方正在通话中',duration: 1.5,});break;case PRIVATE_WEBRTC_ANSWER_TYPE.OFFLINE:globalMessage.error({content: '呼叫的用户不在线',duration: 1.5,});break;case PRIVATE_WEBRTC_ANSWER_TYPE.REJECT:globalMessage.error({content: '对方拒绝了您的通话邀请',duration: 1.5,});break;}this.onEnded();}}});this.socket.on('ON_PRIVATE_WEBRTC_OFFER', (msg) => {if (msg.sender === this.sender && msg.receiver === this.receiver)this.createAnswer(msg.sdp);});this.socket.on('ON_PRIVATE_WEBRTC_ANSWER', (msg) => {this.receiveAnswer(msg.sdp);});this.socket.on('ON_PRIVATE_WEBRTC_CANDIDATE', (msg) => {if (msg.sender === this.sender && msg.receiver === this.receiver) {this.handleCandidate(msg);}});this.socket.on('ON_PRIVATE_WEBRTC_DISCONNECT', (msg) => {globalMessage.info('对方已挂断通话');this.onHangUp(msg);});}callRemote(targetId: number, myName: string, offerModal: any) {this.useSecurity = localStorage.getItem('securityPrivateWebrtc') === 'true';this.callAudioPrompt[0]();store.dispatch(setCallStatus(CALL_STATUS_OFFERING));store.dispatch(setNowWebrtcFriendId(targetId));this.sender = this.myId;this.receiver = targetId;let pgArr: Array<string> = [];(async () => {if (this.useSecurity) {pgArr = await eWindow.ipc.invoke('DIFFIE_HELLMAN');}this.socket.send({type: ChatWebSocketType.CHAT_PRIVATE_WEBRTC_REQUEST,sender: this.myId,senderName: myName,security: JSON.stringify(pgArr),receiver: targetId,});this.offerModal = offerModal;})();}responseCall(msg: any) {this.sender = msg.sender;this.receiver = this.myId;const rejectOffer = (reason: number) => {this.socket.send({type: ChatWebSocketType.CHAT_PRIVATE_WEBRTC_RESPONSE,security: '',accept: reason,sender: msg.sender,receiver: msg.receiver,});};if (store.getState().callStatus === CALL_STATUS_FREE) {eventBus.emit('GET_PRIVATE_CALLED');this.answerAudioPrompt[0]();store.dispatch(setNowChattingId(msg.sender));const pgArr = JSON.parse(msg.security);const useSecurity = pgArr.length === 3;this.answerModal = Modal.confirm({icon: useSecurity ? <AlertOutlined /> : <ExclamationCircleOutlined />,title: '视频通话邀请',content: (<span>用户 {msg.senderName}(id: {msg.sender})向您发出视频通话请求，是否接受？{useSecurity ? (<span><br />注意：对方启用了私聊视频会话加密功能，接受此会话可能会导致您的CPU占用被大幅度提高，请与对方确认后选择是否接受此会话</span>) : ('')}</span>),cancelText: (<><CloseOutlined />拒绝接受</>),okText: (<><CheckOutlined />同意请求</>),onOk: () => {this.useSecurity = useSecurity;if (useSecurity) {eWindow.ipc.invoke('DIFFIE_HELLMAN', pgArr[0], pgArr[1], pgArr[2]).then((serverArr) => {const [privateKey, publicKey] = serverArr;this.security = privateKey;this.socket.send({type: ChatWebSocketType.CHAT_PRIVATE_WEBRTC_RESPONSE,accept: PRIVATE_WEBRTC_ANSWER_TYPE.ACCEPT,sender: this.sender,receiver: this.receiver,security: publicKey,});});} else {this.socket.send({type: ChatWebSocketType.CHAT_PRIVATE_WEBRTC_RESPONSE,accept: PRIVATE_WEBRTC_ANSWER_TYPE.ACCEPT,sender: this.sender,receiver: this.receiver,security: '',});}store.dispatch(setCallStatus(CALL_STATUS_ANSWERING));store.dispatch(setNowWebrtcFriendId(msg.sender));},onCancel: () => {rejectOffer(PRIVATE_WEBRTC_ANSWER_TYPE.REJECT);this.answerModal = null;this.sender = undefined;this.receiver = undefined;},afterClose: this.answerAudioPrompt[1],centered: true,getContainer: getMainContent,});} else rejectOffer(PRIVATE_WEBRTC_ANSWER_TYPE.BUSY);}async createOffer(publicKey: string) {this.peer = this.buildPeer();this.localStream = new MediaStream();this.localStream.addTrack((await getDeviceStream(DEVICE_TYPE.VIDEO_DEVICE)).getVideoTracks()[0]);this.localStream.addTrack((await getDeviceStream(DEVICE_TYPE.AUDIO_DEVICE)).getAudioTracks()[0]);for (const track of this.localStream.getTracks()) {this.peer.addTrack(track, this.localStream);}// NOTE: 加密if (publicKey) {const privateKey = await eWindow.ipc.invoke('DIFFIE_HELLMAN', publicKey);this.security = privateKey;this.peer.getSenders().forEach((sender) => {setupSenderTransform(sender, privateKey);});} else {this.peer.getTransceivers().find((t) => t.sender.track?.kind === 'video')?.setCodecPreferences(senderCodecs);}this.peer.createOffer({offerToReceiveAudio: true,offerToReceiveVideo: true,}).then((sdp) => {this.peer.setLocalDescription(sdp);this.socket.send({type: ChatWebSocketType.CHAT_PRIVATE_WEBRTC_OFFER,sdp: sdp.sdp,sender: this.sender,receiver: this.receiver,});});}async createAnswer(remoteSdp: any) {this.peer = this.buildPeer();this.peer.setRemoteDescription(new RTCSessionDescription({sdp: remoteSdp,type: 'offer',}));while (this.candidateQueue.length > 0) {this.peer.addIceCandidate(this.candidateQueue.shift());}this.localStream = new MediaStream();this.localStream.addTrack((await getDeviceStream(DEVICE_TYPE.VIDEO_DEVICE)).getVideoTracks()[0]);this.localStream.addTrack((await getDeviceStream(DEVICE_TYPE.AUDIO_DEVICE)).getAudioTracks()[0]);this.emit('LOCAL_STREAM_READY', this.localStream);for (const track of this.localStream.getTracks()) {this.peer.addTrack(track, this.localStream);}// NOTE: 加密if (this.useSecurity) {this.peer.getSenders().forEach((sender) => {setupSenderTransform(sender, this.security);});} else {this.peer.getTransceivers().find((t) => t.sender.track?.kind === 'video')?.setCodecPreferences(senderCodecs);}this.peer.createAnswer({mandatory: {OfferToReceiveAudio: true,OfferToReceiveVideo: true,},}).then((sdp) => {this.peer.setLocalDescription(sdp);this.socket.send({type: ChatWebSocketType.CHAT_PRIVATE_WEBRTC_ANSWER,sdp: sdp.sdp,sender: this.sender,receiver: this.receiver,});store.dispatch(setCallStatus(CALL_STATUS_CALLING));});}async receiveAnswer(remoteSdp: any) {this.peer.setRemoteDescription(new RTCSessionDescription({sdp: remoteSdp,type: 'answer',}));store.dispatch(setCallStatus(CALL_STATUS_CALLING));this.emit('LOCAL_STREAM_READY', this.localStream);}handleCandidate(data: RTCIceCandidateInit) {this.candidateQueue = this.candidateQueue || new Array();if (data.candidate) {// NOTE: 需要等待 signalingState 变为 stable 才能添加候选者if (this.peer && this.peer.signalingState === 'stable') {this.peer.addIceCandidate(data);} else {this.candidateQueue.push(data);}}}hangUp() {this.callAudioPrompt[1]();this.socket.send({type: ChatWebSocketType.CHAT_PRIVATE_WEBRTC_DISCONNECT,sender: this.sender,receiver: this.receiver,target: store.getState().nowWebrtcFriendId,});this.offerModal = null;this.onEnded();}onHangUp(data: { sender: number; receiver: number }) {const { sender, receiver } = data;if (sender === this.sender && receiver === this.receiver) {if (this.answerModal) {this.answerAudioPrompt[1]();this.answerModal.destroy();}this.answerModal = null;this.onEnded();}}/*** 创建 RTCPeer 连接* @returns 创建后的 RTCPeer 连接*/private buildPeer(): RTCPeerConnection {const peer = new (RTCPeerConnection as any)({iceServers: [{urls: 'stun:stun.stunprotocol.org:3478',},],encodedInsertableStreams: this.useSecurity,}) as RTCPeerConnection;peer.onicecandidate = (evt) => {if (evt.candidate) {const message = {type: ChatWebSocketType.CHAT_PRIVATE_WEBRTC_CANDIDATE,candidate: evt.candidate.candidate,sdpMid: evt.candidate.sdpMid,sdpMLineIndex: evt.candidate.sdpMLineIndex,sender: this.sender,receiver: this.receiver,target: store.getState().nowWebrtcFriendId,};this.socket.send(message);}};peer.ontrack = (evt) => {// NOTE: 解密if (this.useSecurity) setupReceiverTransform(evt.receiver, this.security);elsepeer.getTransceivers().find((t) => t.receiver.track.kind === 'video')?.setCodecPreferences(receiverCodecs);this.remoteStream = this.remoteStream || new MediaStream();this.remoteStream.addTrack(evt.track);if (this.remoteStream.getTracks().length === 2)this.emit('REMOTE_STREAM_READY', this.remoteStream);};// NOTE: 断连检测peer.oniceconnectionstatechange = () => {if (peer.iceConnectionState === 'disconnected') {this.emit('ICE_DISCONNECT');}};peer.onconnectionstatechange = () => {if (peer.connectionState === 'failed') {this.emit('RTC_CONNECTION_FAILED');}};return peer;}changeVideoTrack(newTrack: MediaStreamTrack) {if (this.localStream && this.peer) {const oldTrack = this.localStream.getVideoTracks()[0];this.localStream.removeTrack(oldTrack);this.localStream.addTrack(newTrack);this.peer.getSenders().find((s) => s.track === oldTrack)?.replaceTrack(newTrack);}}/*** 结束通话后清空数据*/onEnded() {this.sender = undefined;this.receiver = undefined;this.useSecurity = false;this.security = '[]';store.dispatch(setNowWebrtcFriendId(null));this.localStream = null;this.remoteStream = null;if (this.peer) this.peer.close();this.candidateQueue = new Array();store.dispatch(setCallStatus(CALL_STATUS_FREE));}
}

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【山大会议】私人聊天频道 WebRTC 工具类

文章目录

序言

逻辑设计

私人 WebRTC 工具类代码

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