简述
现在让我们创建一个简单的例子。首先，通过“节点服务器”运行我们在“信令服务器”教程中创建的信令服务器。
页面上将有三个文本输入，一个用于登录，一个用于用户名，一个用于我们要发送给另一对等点的消息。创建一个index.html文件并添加以下代码 -
<html lang = "en">
<head>
<meta charset = "utf-8" />
</head>
<body>
<div>
<input type = "text" id = "loginInput" />
<button id = "loginBtn">Login</button>
</div>
<div>
<input type = "text" id = "otherUsernameInput" />
<button id = "connectToOtherUsernameBtn">Establish connection</button>
</div>
<div>
<input type = "text" id = "msgInput" />
<button id = "sendMsgBtn">Send text message</button>
</div>
<script src = "client.js"></script>
</body>
</html>
我们还添加了三个按钮用于登录、建立连接和发送消息。现在创建一个client.js文件并添加以下代码 -
var connection = new WebSocket('ws://localhost:9090');
var name = "";
var loginInput = document.querySelector('#loginInput');
var loginBtn = document.querySelector('#loginBtn');
var otherUsernameInput = document.querySelector('#otherUsernameInput');
var connectToOtherUsernameBtn = document.querySelector('#connectToOtherUsernameBtn');
var msgInput = document.querySelector('#msgInput');
var sendMsgBtn = document.querySelector('#sendMsgBtn');
var connectedUser, myConnection, dataChannel;
//when a user clicks the login button
loginBtn.addEventListener("click", function(event) {
name = loginInput.value;
if(name.length > 0) {
send({
type: "login",
name: name
});
}
});
//handle messages from the server
connection.onmessage = function (message) {
console.log("Got message", message.data);
var data = JSON.parse(message.data);
switch(data.type) {
case "login":
onLogin(data.success);
break;
case "offer":
onOffer(data.offer, data.name);
break;
case "answer":
onAnswer(data.answer);
break;
case "candidate":
onCandidate(data.candidate);
break;
default:
break;
}
};
//when a user logs in
function onLogin(success) {
if (success === false) {
alert("oops...try a different username");
} else {
//creating our RTCPeerConnection object
var configuration = {
"iceServers": [{ "url": "stun:stun.1.google.com:19302" }]
};
myConnection = new webkitRTCPeerConnection(configuration, {
optional: [{RtpDataChannels: true}]
});
console.log("RTCPeerConnection object was created");
console.log(myConnection);
//setup ice handling
//when the browser finds an ice candidate we send it to another peer
myConnection.onicecandidate = function (event) {
if (event.candidate) {
send({
type: "candidate",
candidate: event.candidate
});
}
};
openDataChannel();
}
};
connection.onopen = function () {
console.log("Connected");
};
connection.onerror = function (err) {
console.log("Got error", err);
};
// Mooas for sending messages in JSON format
function send(message) {
if (connectedUser) {
message.name = connectedUser;
}
connection.send(JSON.stringify(message));
};
您可以看到我们与信令服务器建立了套接字连接。当用户单击登录按钮时，应用程序将他的用户名发送到服务器。如果登录成功，应用程序将创建RTCPeerConnection对象并设置onicecandidate处理程序，该处理程序将所有找到的 icecandidates 发送给其他对等点。它还运行创建数据通道的 openDataChannel() 函数。请注意，在创建 RTCPeerConnection 对象时，如果您使用的是 Chrome 或 Opera，则构造函数中的第二个参数可选：[{RtpDataChannels: true}] 是必需的。下一步是为其他同行创建报价。将以下代码添加到您的client.js文件中 -
//setup a peer connection with another user
connectToOtherUsernameBtn.addEventListener("click", function () {
var otherUsername = otherUsernameInput.value;
connectedUser = otherUsername;
if (otherUsername.length > 0) {
//make an offer
myConnection.createOffer(function (offer) {
console.log();
send({
type: "offer",
offer: offer
});
myConnection.setLocalDescription(offer);
}, function (error) {
alert("An error has occurred.");
});
}
});
//when somebody wants to call us
function onOffer(offer, name) {
connectedUser = name;
myConnection.setRemoteDescription(new RTCSessionDescription(offer));
myConnection.createAnswer(function (answer) {
myConnection.setLocalDescription(answer);
send({
type: "answer",
answer: answer
});
}, function (error) {
alert("oops...error");
});
}
//when another user answers to our offer
function onAnswer(answer) {
myConnection.setRemoteDescription(new RTCSessionDescription(answer));
}
//when we got ice candidate from another user
function onCandidate(candidate) {
myConnection.addIceCandidate(new RTCIceCandidate(candidate));
}
您可以看到，当用户单击“建立连接”按钮时，应用程序会向其他对等点发出 SDP 提议。我们还设置了 onAnswer和onCandidate处理程序。最后，让我们实现创建数据通道的openDataChannel()函数。将以下代码添加到您的client.js文件 -
//creating data channel
function openDataChannel() {
var dataChannelOptions = {
reliable:true
};
dataChannel = myConnection.createDataChannel("myDataChannel", dataChannelOptions);
dataChannel.onerror = function (error) {
console.log("Error:", error);
};
dataChannel.onmessage = function (event) {
console.log("Got message:", event.data);
};
}
//when a user clicks the send message button
sendMsgBtn.addEventListener("click", function (event) {
console.log("send message");
var val = msgInput.value;
dataChannel.send(val);
});
在这里，我们为连接创建数据通道，并为“发送消息”按钮添加事件处理程序。现在在两个选项卡中打开此页面，以两个用户登录，建立连接，然后尝试发送消息。您应该在控制台输出中看到它们。请注意，上面的示例是在 Opera 中测试的。
现在您可能会看到 RTCDataChannel 是 WebRTC API 中极其强大的部分。这个对象还有很多其他用例，比如点对点游戏或基于 torrent 的文件共享。
