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RTCEngine.ts
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RTCEngine.ts
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import { EventEmitter } from 'events';
import log from 'loglevel';
import { SignalClient, SignalOptions } from '../api/SignalClient';
import { TrackInfo } from '../proto/livekit_models';
import {
AddTrackRequest,
DataPacket,
JoinResponse,
SignalTarget,
TrackPublishedResponse,
} from '../proto/livekit_rtc';
import { ConnectionError, TrackInvalidError, UnexpectedConnectionState } from './errors';
import { EngineEvent } from './events';
import PCTransport from './PCTransport';
import { sleep, useLegacyAPI } from './utils';
const lossyDataChannel = '_lossy';
const reliableDataChannel = '_reliable';
const maxReconnectRetries = 5;
export default class RTCEngine extends EventEmitter {
publisher?: PCTransport;
subscriber?: PCTransport;
client: SignalClient;
rtcConfig: RTCConfiguration;
useLegacy: boolean;
lossyDC?: RTCDataChannel;
reliableDC?: RTCDataChannel;
iceConnected: boolean = false;
isClosed: boolean = true;
pendingTrackResolvers: { [key: string]: (info: TrackInfo) => void } = {};
// keep join info around for reconnect
url?: string;
token?: string;
reconnectAttempts: number = 0;
constructor(client: SignalClient, config?: RTCConfiguration) {
super();
this.client = client;
this.rtcConfig = config || {};
this.useLegacy = useLegacyAPI();
log.trace('creating RTCEngine', 'useLegacy', this.useLegacy);
}
async join(url: string, token: string, opts?: SignalOptions): Promise<JoinResponse> {
this.url = url;
this.token = token;
const joinResponse = await this.client.join(url, token, this.useLegacy, opts);
this.isClosed = false;
if (joinResponse.iceServers && !this.rtcConfig.iceServers) {
const rtcIceServers: RTCIceServer[] = [];
joinResponse.iceServers.forEach((iceServer) => {
const rtcIceServer: RTCIceServer = {
urls: iceServer.urls,
};
if (iceServer.username) rtcIceServer.username = iceServer.username;
if (iceServer.credential) { rtcIceServer.credential = iceServer.credential; }
rtcIceServers.push(rtcIceServer);
});
this.rtcConfig.iceServers = rtcIceServers;
}
// update ICE servers before creating PeerConnection
if (!this.publisher) {
const conf: any = this.rtcConfig;
if (this.useLegacy) {
conf.sdpSemantics = 'plan-b';
}
this.publisher = new PCTransport(this.rtcConfig);
this.subscriber = new PCTransport(this.rtcConfig);
this.configure();
}
// create offer
await this.negotiate();
return joinResponse;
}
close() {
this.isClosed = true;
if (this.publisher) {
this.publisher.pc.getSenders().forEach((sender) => {
try {
this.publisher?.pc.removeTrack(sender);
} catch (e) {
log.warn('could not removeTrack', e);
}
});
this.publisher.close();
this.publisher = undefined;
}
if (this.subscriber) {
this.subscriber.close();
this.subscriber = undefined;
}
this.client.close();
}
addTrack(req: AddTrackRequest): Promise<TrackInfo> {
if (this.pendingTrackResolvers[req.cid]) {
throw new TrackInvalidError(
'a track with the same ID has already been published',
);
}
return new Promise<TrackInfo>((resolve) => {
this.pendingTrackResolvers[req.cid] = resolve;
this.client.sendAddTrack(req);
});
}
updateMuteStatus(trackSid: string, muted: boolean) {
this.client.sendMuteTrack(trackSid, muted);
}
private configure() {
if (!this.publisher || !this.subscriber) {
return;
}
this.publisher.pc.onicecandidate = (ev) => {
if (!ev.candidate) return;
log.trace('adding ICE candidate for peer', ev.candidate);
this.client.sendIceCandidate(ev.candidate, SignalTarget.PUBLISHER);
};
this.subscriber.pc.onicecandidate = (ev) => {
if (!ev.candidate) return;
this.client.sendIceCandidate(ev.candidate, SignalTarget.SUBSCRIBER);
};
this.publisher.pc.onnegotiationneeded = () => {
if (this.publisher?.pc.iceConnectionState === 'new') {
return;
}
this.negotiate();
};
this.publisher.pc.oniceconnectionstatechange = () => {
if (!this.publisher) {
return;
}
if (this.publisher.pc.iceConnectionState === 'connected') {
log.trace('ICE connected');
if (!this.iceConnected) {
this.iceConnected = true;
this.emit(EngineEvent.Connected);
}
} else if (this.publisher.pc.iceConnectionState === 'failed') {
this.iceConnected = false;
log.trace('ICE disconnected');
this.handleDisconnect('peerconnection');
}
};
if (this.useLegacy) {
this.subscriber.pc.addEventListener('addstream', (ev: any) => {
const { stream } = ev;
stream.getTracks().forEach((t: MediaStreamTrack) => {
this.emitTrackEvent(t, stream);
});
});
} else {
this.subscriber.pc.ontrack = (ev: RTCTrackEvent) => {
this.emitTrackEvent(ev.track, ev.streams[0], ev.receiver);
};
}
// data channels
this.lossyDC = this.publisher.pc.createDataChannel(lossyDataChannel, {
// will drop older packets that arrive
ordered: true,
maxRetransmits: 1,
});
this.reliableDC = this.publisher.pc.createDataChannel(reliableDataChannel, {
ordered: true,
});
this.lossyDC.onmessage = this.handleDataMessage;
this.reliableDC.onmessage = this.handleDataMessage;
// configure signaling client
this.client.onAnswer = async (sd) => {
if (!this.publisher) {
return;
}
log.debug(
'received server answer',
sd.type,
this.publisher.pc.signalingState,
);
await this.publisher.setRemoteDescription(sd);
};
// add candidate on trickle
this.client.onTrickle = (candidate, target) => {
if (!this.publisher || !this.subscriber) {
return;
}
log.trace('got ICE candidate from peer', candidate, target);
if (target === SignalTarget.PUBLISHER) {
this.publisher.addIceCandidate(candidate);
} else {
this.subscriber.addIceCandidate(candidate);
}
};
// when server creates an offer for the client
this.client.onOffer = async (sd) => {
if (!this.subscriber) {
return;
}
log.debug(
'received server offer',
sd.type,
this.subscriber.pc.signalingState,
);
await this.subscriber.setRemoteDescription(sd);
// answer the offer
const answer = await this.subscriber.pc.createAnswer();
await this.subscriber.pc.setLocalDescription(answer);
this.client.sendAnswer(answer);
};
this.client.onParticipantUpdate = (updates) => {
this.emit(EngineEvent.ParticipantUpdate, updates);
};
this.client.onLocalTrackPublished = (res: TrackPublishedResponse) => {
const resolve = this.pendingTrackResolvers[res.cid];
if (!resolve) {
log.error('missing track resolver for ', res.cid);
return;
}
delete this.pendingTrackResolvers[res.cid];
resolve(res.track!);
};
this.client.onActiveSpeakersChanged = (speakers) => {
this.emit(EngineEvent.SpeakersUpdate, speakers);
};
this.client.onClose = () => {
this.handleDisconnect('signal');
};
this.client.onLeave = () => {
this.close();
this.emit(EngineEvent.Disconnected);
};
}
private handleDataMessage = async (message: MessageEvent) => {
// decode
let buffer: ArrayBuffer | undefined;
if (message.data instanceof ArrayBuffer) {
buffer = message.data;
} else if (message.data instanceof Blob) {
buffer = await message.data.arrayBuffer();
} else {
log.error('unsupported data type', message.data);
return;
}
const dp = DataPacket.decode(new Uint8Array(buffer));
if (dp.speaker) {
// dispatch speaker updates
this.emit(EngineEvent.SpeakersUpdate, dp.speaker.speakers);
} else if (dp.user) {
this.emit(EngineEvent.DataPacketReceived, dp.user, dp.kind);
}
};
// websocket reconnect behavior. if websocket is interrupted, and the PeerConnection
// continues to work, we can reconnect to websocket to continue the session
// after a number of retries, we'll close and give up permanently
private handleDisconnect = (connection: string) => {
if (this.isClosed) {
return;
}
log.debug(`${connection} disconnected`);
if (this.reconnectAttempts >= maxReconnectRetries) {
log.info(
'could not connect to signal after',
maxReconnectRetries,
'attempts. giving up',
);
this.close();
this.emit(EngineEvent.Disconnected);
return;
}
const delay = (this.reconnectAttempts * this.reconnectAttempts) * 300;
setTimeout(() => {
this.reconnect()
.then(() => {
this.reconnectAttempts = 0;
})
.catch(this.handleDisconnect);
}, delay);
};
private async reconnect(): Promise<void> {
if (this.isClosed) {
return;
}
if (!this.url || !this.token) {
throw new ConnectionError('could not reconnect, url or token not saved');
}
log.info('reconnecting to signal connection, attempt', this.reconnectAttempts);
if (this.reconnectAttempts === 0) {
this.emit(EngineEvent.Reconnecting);
}
this.reconnectAttempts += 1;
await this.client.reconnect(this.url, this.token);
// trigger publisher reconnect
if (!this.publisher || !this.subscriber) {
throw new UnexpectedConnectionState('publisher and subscriber connections unset');
}
this.publisher.restartingIce = true;
this.subscriber.restartingIce = true;
// @ts-ignore
if (this.publisher.pc.restartIce) {
// @ts-ignore
this.publisher.pc.restartIce();
} else {
await this.negotiate({ iceRestart: true });
}
const startTime = (new Date()).getTime();
while ((new Date()).getTime() - startTime < 10 * 1000) {
if (this.iceConnected) {
// reconnect success
this.emit(EngineEvent.Reconnected);
return;
}
await sleep(100);
}
// have not reconnected, throw
throw new ConnectionError('could not establish ICE connection');
}
private async negotiate(options?: RTCOfferOptions) {
if (!this.publisher) {
return;
}
const { pc } = this.publisher;
if (pc.remoteDescription && pc.signalingState === 'have-local-offer') {
// it's still waiting for the last offer, and it won't be able to create
// a new offer in this state. We'll reuse the last remote description to
// get it out of this state
await pc.setRemoteDescription(pc.remoteDescription);
}
// TODO: what if signaling state changed? will need to queue and retry
log.debug('starting to negotiate', pc.signalingState);
const offer = await pc.createOffer(options);
await pc.setLocalDescription(offer);
this.client.sendOffer(offer);
}
private emitTrackEvent = (
track: MediaStreamTrack,
stream: MediaStream,
receiver?: RTCRtpReceiver,
) => {
this.emit(EngineEvent.MediaTrackAdded, track, stream, receiver);
};
}