/ WebRTC  

webrtc使用RTCDataChannel交换数据

demo内容

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<!DOCTYPE html>
<html>
<head>
<title>demo2</title>
</head>
<style>
</style>
<body>
<textarea id="dataChannelSend" disabled
placeholder="Press Start, enter some text, then press Send."></textarea>
<textarea id="dataChannelReceive" disabled></textarea>

<div id="buttons">
<button id="startButton">Start</button>
<button id="sendButton">Send</button>
<button id="closeButton">Stop</button>
</div>
</body>

<script src="https://webrtc.github.io/adapter/adapter-latest.js"></script>
<script type="text/javascript">
'use strict';

let localConnection;
let remoteConnection;
let sendChannel;
let receiveChannel;
const dataChannelSend = document.querySelector('textarea#dataChannelSend');
const dataChannelReceive = document.querySelector('textarea#dataChannelReceive');
const startButton = document.querySelector('button#startButton');
const sendButton = document.querySelector('button#sendButton');
const closeButton = document.querySelector('button#closeButton');

startButton.onclick = createConnection;
sendButton.onclick = sendData;
closeButton.onclick = closeDataChannels;

function enableStartButton() {
startButton.disabled = false;
}

function disableSendButton() {
sendButton.disabled = true;
}

function createConnection() {
dataChannelSend.placeholder = '';
const servers = null;
window.localConnection = localConnection = new RTCPeerConnection(servers);
console.log('Created local peer connection object localConnection');

sendChannel = localConnection.createDataChannel('sendDataChannel');
console.log('Created send data channel');

localConnection.onicecandidate = e => {
onIceCandidate(localConnection, e);
};
sendChannel.onopen = onSendChannelStateChange;
sendChannel.onclose = onSendChannelStateChange;

window.remoteConnection = remoteConnection = new RTCPeerConnection(servers);
console.log('Created remote peer connection object remoteConnection');

remoteConnection.onicecandidate = e => {
onIceCandidate(remoteConnection, e);
};
remoteConnection.ondatachannel = receiveChannelCallback;

localConnection.createOffer().then(
gotDescription1,
onCreateSessionDescriptionError
);
startButton.disabled = true;
closeButton.disabled = false;
}

function onCreateSessionDescriptionError(error) {
console.log('Failed to create session description: ' + error.toString());
}

function sendData() {
const data = dataChannelSend.value;
sendChannel.send(data);
console.log('Sent Data: ' + data);
}

function closeDataChannels() {
console.log('Closing data channels');
sendChannel.close();
console.log('Closed data channel with label: ' + sendChannel.label);
receiveChannel.close();
console.log('Closed data channel with label: ' + receiveChannel.label);
localConnection.close();
remoteConnection.close();
localConnection = null;
remoteConnection = null;
console.log('Closed peer connections');
startButton.disabled = false;
sendButton.disabled = true;
closeButton.disabled = true;
dataChannelSend.value = '';
dataChannelReceive.value = '';
dataChannelSend.disabled = true;
disableSendButton();
enableStartButton();
}

function gotDescription1(desc) {
localConnection.setLocalDescription(desc);
console.log(`Offer from localConnection\n${desc.sdp}`);
remoteConnection.setRemoteDescription(desc);
remoteConnection.createAnswer().then(
gotDescription2,
onCreateSessionDescriptionError
);
}

function gotDescription2(desc) {
remoteConnection.setLocalDescription(desc);
console.log(`Answer from remoteConnection\n${desc.sdp}`);
localConnection.setRemoteDescription(desc);
}

function getOtherPc(pc) {
return (pc === localConnection) ? remoteConnection : localConnection;
}

function getName(pc) {
return (pc === localConnection) ? 'localPeerConnection' : 'remotePeerConnection';
}

function onIceCandidate(pc, event) {
getOtherPc(pc)
.addIceCandidate(event.candidate)
.then(
() => onAddIceCandidateSuccess(pc),
err => onAddIceCandidateError(pc, err)
);
console.log(`${getName(pc)} ICE candidate: ${event.candidate ? event.candidate.candidate : '(null)'}`);
}

function onAddIceCandidateSuccess() {
console.log('AddIceCandidate success.');
}

function onAddIceCandidateError(error) {
console.log(`Failed to add Ice Candidate: ${error.toString()}`);
}

function receiveChannelCallback(event) {
console.log('Receive Channel Callback');
receiveChannel = event.channel;
receiveChannel.onmessage = onReceiveMessageCallback;
receiveChannel.onopen = onReceiveChannelStateChange;
receiveChannel.onclose = onReceiveChannelStateChange;
}

function onReceiveMessageCallback(event) {
console.log('Received Message');
dataChannelReceive.value = event.data;
}

function onSendChannelStateChange() {
const readyState = sendChannel.readyState;
console.log('Send channel state is: ' + readyState);
if (readyState === 'open') {
dataChannelSend.disabled = false;
dataChannelSend.focus();
sendButton.disabled = false;
closeButton.disabled = false;
} else {
dataChannelSend.disabled = true;
sendButton.disabled = true;
closeButton.disabled = true;
}
}

function onReceiveChannelStateChange() {
const readyState = receiveChannel.readyState;
console.log(`Receive channel state is: ${readyState}`);
}
</script>

</html>

工作原理

此代码使用RTCPeerConnection和RTCDataChannel来启用文本消息的交换。

此步骤中的大部分代码与RTCPeerConnection示例相同。

RTCDataChannel的语法有意类似于WebSocket,带有send()方法和消息事件。

注意dataConstraint的使用。可以配置数据通道以实现不同类型的数据共享 - 例如,优先考虑可靠的交付而不是性能。您可以在Mozilla Developer Network上找到有关选项的更多信息。

加分项

  1. WebRTC数据通道使用的协议使用SCTP,默认使用可靠和有序的数据传输。在 RTCDataChannel 需要提供可靠的数据传输时或更重要的信息时使用它, 即使这可能意味着丢失一部分数据。查阅为什么使用sctp传输?
  2. 使用CSS改进页面布局,并将“占位符”属性添加到“dataChannelReceive”textarea。
  3. 在移动设备上测试页面。