在本章中，我们将构建一个客户端应用程序，允许不同设备上的两个用户使用WebRTC相互发送消息.我们的申请将有两页.一个用于登录，另一个用于向另一个用户发送消息.
这两个页面将是 div 标签.大多数输入是通过简单的事件处理程序完成的.
要创建WebRTC连接，客户端必须能够在不使用WebRTC的情况下传输邮件同伴连接.这是我们将使用HTML5 WebSockets : 两个端点之间的双向套接字连接 : Web服务器和Web浏览器.现在让我们开始使用WebSocket库.创建 server.js 文件并插入以下代码 :
//require our websocket library
var WebSocketServer = require('ws').Server;
//creating a websocket server at port 9090
var wss = new WebSocketServer({port: 9090});
//when a user connects to our sever
wss.on('connection', function(connection) {
console.log("user connected");
//when server gets a message from a connected user
connection.on('message', function(message) {
console.log("Got message from a user:", message);
});
connection.send("Hello from server");
});第一行需要我们已安装的WebSocket库.然后我们在端口9090上创建一个套接字服务器.接下来，我们监听 connection 事件.当用户与服务器建立WebSocket连接时，将执行此代码.然后我们收听用户发送的任何消息.最后，我们向连接的用户发送一个回复，说"来自服务器的Hello".
在我们的信令服务器中，我们将为每个连接使用基于字符串的用户名，以便我们知道在哪里发送消息.让我们稍微改变我们的连接处理程序;
connection.on('message', function(message) {
var data;
//accepting only JSON messages
try {
data = JSON.parse(message);
} catch (e) {
console.log("Invalid JSON");
data = {};
}
});这样我们只接受JSON消息.接下来，我们需要将所有连接的用户存储在某个地方.我们将使用一个简单的Javascript对象.更改我们文件的顶部 :
//require our websocket library
var WebSocketServer = require('ws').Server;
//creating a websocket server at port 9090
var wss = new WebSocketServer({port: 9090});
//all connected to the server users
var users = {};我们将为来自客户端的每条消息添加类型字段.例如，如果用户想要登录，则他发送登录类型的消息.让我们定义它 :
connection.on('message', function(message) {
var data;
//accepting only JSON messages
try {
data = JSON.parse(message);
} catch (e) {
console.log("Invalid JSON");
data = {};
}
//switching type of the user message
switch (data.type) {
//when a user tries to login
case "login":
console.log("User logged:", data.name);
//if anyone is logged in with this username then refuse
if(users[data.name]) {
sendTo(connection, {
type: "login",
success: false
});
} else {
//save user connection on the server
users[data.name] = connection;
connection.name = data.name;
sendTo(connection, {
type: "login",
success: true
});
}
break;
default:
sendTo(connection, {
type: "error",
message: "Command no found: " + data.type
});
break;
}
});如果用户发送带有登录类型的消息，我们 :
检查是否有人已使用此用户名登录.
如果是，请告诉用户他尚未成功登录.
如果没有人使用此用户名，我们会将用户名添加为连接对象的密钥.
如果命令无法识别，我们发送一个错误.
以下代码是用于向连接发送消息的辅助函数.将其添加到 server.js 文件 :
function sendTo(connection, message) {
connection.send(JSON.stringify(message));
}当用户断开连接时，我们应该清理它的连接.我们可以在触发关闭事件时删除用户.将以下代码添加到连接处理程序 :
connection.on("close", function() {
if(connection.name) {
delete users[connection.name];
}
});成功登录后，用户想要拨打另一个.他应该向另一个用户提出 offer 来实现它.添加 offer 处理程序 :
case "offer":
//for ex. UserA wants to call UserB
console.log("Sending offer to: ", data.name);
//if UserB exists then send him offer details
var conn = users[data.name];
if(conn != null){
//setting that UserA connected with UserB
connection.otherName = data.name;
sendTo(conn, {
type: "offer",
offer: data.offer,
name: connection.name
});
break;首先，我们得到我们试图呼叫的用户的连接.如果它存在，我们发送 offer 详细信息.我们还将 otherName 添加到 connection 对象.这是为了以后查找它的简单性.
回答响应的模式类似于我们在 offer 处理程序中使用的模式.我们的服务器只是将回答的所有消息传递给另一个用户.在 offer 处理程序 :
case "answer":
console.log("Sending answer to: ", data.name);
//for ex. UserB answers UserA
var conn = users[data.name];
if(conn != null) {
connection.otherName = data.name;
sendTo(conn, {
type: "answer",
answer: data.answer
});
}
break;最后一部分是处理用户之间的ICE候选者.我们使用相同的技术只是在用户之间传递消息.主要区别在于候选消息可能以任何顺序每个用户多次发生.添加候选人处理程序 :
case "candidate":
console.log("Sending candidate to:",data.name);
var conn = users[data.name];
if(conn != null) {
sendTo(conn, {
type: "candidate",
candidate: data.candidate
});
}
break;为了让我们的用户与其他用户断开连接，我们应该实现挂机功能.它还会告诉服务器删除所有用户引用.添加离开处理程序 :
case "leave":
console.log("Disconnecting from", data.name);
var conn = users[data.name];
conn.otherName = null;
//notify the other user so he can disconnect his peer connection
if(conn != null) {
sendTo(conn, {
type: "leave"
});
}
break;这也将向其他用户发送离开事件，以便他可以相应地断开他的对等连接.当用户从信令服务器断开连接时，我们也应该处理这种情况.让我们修改我们的关闭处理程序 : 去;
connection.on("close", function() {
if(connection.name) {
delete users[connection.name];
if(connection.otherName) {
console.log("Disconnecting from ", connection.otherName);
var conn = users[connection.otherName];
conn.otherName = null;
if(conn != null) {
sendTo(conn, {
type: "leave"
});
}
}
}
});以下是我们信令服务器的整个代码 :
//require our websocket library
var WebSocketServer = require('ws').Server;
//creating a websocket server at port 9090
var wss = new WebSocketServer({port: 9090});
//all connected to the server users
var users = {};
//when a user connects to our sever
wss.on('connection', function(connection) {
console.log("User connected");
//when server gets a message from a connected user
connection.on('message', function(message) {
var data;
//accepting only JSON messages
try {
data = JSON.parse(message);
} catch (e) {
console.log("Invalid JSON");
data = {};
}
//switching type of the user message
switch (data.type) {
//when a user tries to login
case "login":
console.log("User logged", data.name);
//if anyone is logged in with this username then refuse
if(users[data.name]) {
sendTo(connection, {
type: "login",
success: false
});
} else {
//save user connection on the server
users[data.name] = connection;
connection.name = data.name;
sendTo(connection, {
type: "login",
success: true
});
}
break;
case "offer":
//for ex. UserA wants to call UserB
console.log("Sending offer to: ", data.name);
//if UserB exists then send him offer details
var conn = users[data.name];
if(conn != null) {
//setting that UserA connected with UserB
connection.otherName = data.name;
sendTo(conn, {
type: "offer",
offer: data.offer,
name: connection.name
});
}
break;
case "answer":
console.log("Sending answer to: ", data.name);
//for ex. UserB answers UserA
var conn = users[data.name];
if(conn != null) {
connection.otherName = data.name;
sendTo(conn, {
type: "answer",
answer: data.answer
});
}
break;
case "candidate":
console.log("Sending candidate to:",data.name);
var conn = users[data.name];
if(conn != null) {
sendTo(conn, {
type: "candidate",
candidate: data.candidate
});
}
break;
case "leave":
console.log("Disconnecting from", data.name);
var conn = users[data.name];
conn.otherName = null;
//notify the other user so he can disconnect his peer connection
if(conn != null) {
sendTo(conn, {
type: "leave"
});
}
break;
default:
sendTo(connection, {
type: "error",
message: "Command not found: " + data.type
});
break;
}
});
//when user exits, for example closes a browser window
//this may help if we are still in "offer","answer" or "candidate" state
connection.on("close", function() {
if(connection.name) {
delete users[connection.name];
if(connection.otherName) {
console.log("Disconnecting from ", connection.otherName);
var conn = users[connection.otherName];
conn.otherName = null;
if(conn != null) {
sendTo(conn, {
type: "leave"
});
}
}
}
});
connection.send("Hello world");
});
function sendTo(connection, message) {
connection.send(JSON.stringify(message));
}测试此应用程序的一种方法是打开两个浏览器选项卡并尝试彼此发送消息.
首先，我们需要安装 bootstrap 库. Bootstrap是用于开发Web应用程序的前端框架.您可以在 http://getbootstrap.com/.了解更多信息.创建一个名为的文件夹，例如，"textchat".这将是我们的根应用程序文件夹.在此文件夹中创建一个文件 package.json (这是管理npm依赖项所必需的)并添加以下 :
{
"name": "webrtc-textochat",
"version": "0.1.0",
"description": "webrtc-textchat",
"author": "Author",
"license": "BSD-2-Clause"
}然后运行 npm install bootstrap .这将在 textchat/node_modules 文件夹中安装引导程序库.
现在我们需要创建一个基本的HTML页面.在根文件夹中使用以下代码创建 index.html 文件 :
<html>
<head>
<title>WebRTC Text Demo</title>
<link rel = "stylesheet" href = "node_modules/bootstrap/dist/css/bootstrap.min.css"/>
</head>
<style>
body {
background: #eee;
padding: 5% 0;
}
</style>
<body>
<div id = "loginPage" class = "container text-center">
<div class = "row">
<div class = "col-md-4 col-md-offset-4">
<h2>WebRTC Text Demo. Please sign in</h2>
<label for = "usernameInput" class = "sr-only">Login</label>
<input type = "email" id = "usernameInput"
class = "form-control formgroup" placeholder = "Login"
required = "" autofocus = "">
<button id = "loginBtn" class = "btn btn-lg btn-primary btnblock">
Sign in</button>
</div>
</div>
</div>
<div id = "callPage" class = "call-page container">
<div class = "row">
<div class = "col-md-4 col-md-offset-4 text-center">
<div class = "panel panel-primary">
<div class = "panel-heading">Text chat</div>
<div id = "chatarea" class = "panel-body text-left"></div>
</div>
</div>
</div>
<div class = "row text-center form-group">
<div class = "col-md-12">
<input id = "callToUsernameInput" type = "text"
placeholder = "username to call" />
<button id = "callBtn" class = "btn-success btn">Call</button>
<button id = "hangUpBtn" class = "btn-danger btn">Hang Up</button>
</div>
</div>
<div class = "row text-center">
<div class = "col-md-12">
<input id = "msgInput" type = "text" placeholder = "message" />
<button id = "sendMsgBtn" class = "btn-success btn">Send</button>
</div>
</div>
</div>
<script src = "client.js"></script>
</body>
</html>您应该熟悉此页面.我们添加了 bootstrap css文件.我们还定义了两个页面.最后，我们创建了几个文本字段和按钮，用于从用户获取信息.在"聊天"页面上，您应该看到带有"chatarea"ID的div标签，其中将显示所有消息.请注意，我们已添加指向 client.js 文件的链接.
现在我们需要与我们的信令服务器建立连接.在根文件夹中使用以下代码创建 client.js 文件 :
//our username
var name;
var connectedUser;
//connecting to our signaling server
var conn = new WebSocket('ws://localhost:9090');
conn.onopen = function () {
console.log("Connected to the signaling server");
};
//when we got a message from a signaling server
conn.onmessage = function (msg) {
console.log("Got message", msg.data);
var data = JSON.parse(msg.data);
switch(data.type) {
case "login":
handleLogin(data.success);
break;
//when somebody wants to call us
case "offer":
handleOffer(data.offer, data.name);
break;
case "answer":
handleAnswer(data.answer);
break;
//when a remote peer sends an ice candidate to us
case "candidate":
handleCandidate(data.candidate);
break;
case "leave":
handleLeave();
break;
default:
break;
}
};
conn.onerror = function (err) {
console.log("Got error", err);
};
//alias for sending JSON encoded messages
function send(message) {
//attach the other peer username to our messages
if (connectedUser) {
message.name = connectedUser;
}
conn.send(JSON.stringify(message));
};现在通过节点服务器运行我们的信令服务器.然后，在根文件夹内运行 static 命令并在浏览器中打开页面.您应该看到以下控制台输出 :
下一步是使用唯一的用户名实现用户登录.我们只需向服务器发送一个用户名，然后告诉我们是否采用了该用户名.将以下代码添加到 client.js 文件 :
//******
//UI selectors block
//******
var loginPage = document.querySelector('#loginPage');
var usernameInput = document.querySelector('#usernameInput');
var loginBtn = document.querySelector('#loginBtn');
var callPage = document.querySelector('#callPage');
var callToUsernameInput = document.querySelector('#callToUsernameInput');
var callBtn = document.querySelector('#callBtn');
var hangUpBtn = document.querySelector('#hangUpBtn');
callPage.style.display = "none";
// Login when the user clicks the button
loginBtn.addEventListener("click", function (event) {
name = usernameInput.value;
if (name.length > 0) {
send({
type: "login",
name: name
});
}
});
function handleLogin(success) {
if (success === false) {
alert("Ooops...try a different username");
} else {
loginPage.style.display = "none";
callPage.style.display = "block";
//**********************
//Starting a peer connection
//**********************
}
};首先，我们选择对页面元素的一些引用.我们隐藏了呼叫页面.然后，我们在登录按钮上添加一个事件监听器.当用户点击它时，我们将他的用户名发送到服务器.最后，我们实现了handleLogin回调.如果登录成功，我们将显示呼叫页面，设置对等连接，并创建数据通道.
要启动与数据通道的对等连接，我们需要 :
创建RTCPeerConnection对象
在我们的RTCPeerConnection对象中创建数据通道
将以下代码添加到"UI选择器块" :
var msgInput = document.querySelector('#msgInput');
var sendMsgBtn = document.querySelector('#sendMsgBtn');
var chatArea = document.querySelector('#chatarea');
var yourConn;
var dataChannel;修改 handleLogin 功能 :
function handleLogin(success) {
if (success === false) {
alert("Ooops...try a different username");
} else {
loginPage.style.display = "none";
callPage.style.display = "block";
//**********************
//Starting a peer connection
//**********************
//using Google public stun server
var configuration = {
"iceServers": [{ "url": "stun:stun2.1.google.com:19302" }]
};
yourConn = new webkitRTCPeerConnection(configuration, {optional: [{RtpDataChannels: true}]});
// Setup ice handling
yourConn.onicecandidate = function (event) {
if (event.candidate) {
send({
type: "candidate",
candidate: event.candidate
});
}
};
//creating data channel
dataChannel = yourConn.createDataChannel("channel1", {reliable:true});
dataChannel.onerror = function (error) {
console.log("Ooops...error:", error);
};
//when we receive a message from the other peer, display it on the screen
dataChannel.onmessage = function (event) {
chatArea.innerHTML += connectedUser + ": " + event.data + "<br />";
};
dataChannel.onclose = function () {
console.log("data channel is closed");
};
}
};如果登录成功，应用程序将创建 RTCPeerConnection 对象并设置 onicecandidate 处理程序，该处理程序将发送所有已找到的内容icecandidates到另一个同行.它还会创建一个dataChannel.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.下一步是为其他对等方创建要约.一旦用户获得报价，他就会创建回答并开始交易ICE候选人.将以下代码添加到 client.js 文件 :
//initiating a call
callBtn.addEventListener("click", function () {
var callToUsername = callToUsernameInput.value;
if (callToUsername.length > 0) {
connectedUser = callToUsername;
// create an offer
yourConn.createOffer(function (offer) {
send({
type: "offer",
offer: offer
});
yourConn.setLocalDescription(offer);
}, function (error) {
alert("Error when creating an offer");
});
}
});
//when somebody sends us an offer
function handleOffer(offer, name) {
connectedUser = name;
yourConn.setRemoteDescription(new RTCSessionDescription(offer));
//create an answer to an offer
yourConn.createAnswer(function (answer) {
yourConn.setLocalDescription(answer);
send({
type: "answer",
answer: answer
});
}, function (error) {
alert("Error when creating an answer");
});
};
//when we got an answer from a remote user
function handleAnswer(answer) {
yourConn.setRemoteDescription(new RTCSessionDescription(answer));
};
//when we got an ice candidate from a remote user
function handleCandidate(candidate) {
yourConn.addIceCandidate(new RTCIceCandidate(candidate));
};我们在"呼叫"按钮上添加了一个单击处理程序，该按钮启动了优惠.然后我们实现了 onmessage 处理程序所期望的几个处理程序.它们将被异步处理，直到两个用户都建立了连接.
下一步是实现挂断功能.这将停止传输数据并告诉其他用户关闭数据通道.添加以下代码 :
//hang up
hangUpBtn.addEventListener("click", function () {
send({
type: "leave"
});
handleLeave();
});
function handleLeave() {
connectedUser = null;
yourConn.close();
yourConn.onicecandidate = null;
};当用户点击挂断按钮 :
它会向其他用户发送"离开"消息.
它将关闭RTCPeerConnection以及数据通道.
最后一步是向另一个对等体发送消息.将"click"处理程序添加到"发送消息"按钮 :
//when user clicks the "send message" button
sendMsgBtn.addEventListener("click", function (event) {
var val = msgInput.value;
chatArea.innerHTML += name + ": " + val + "<br />";
//sending a message to a connected peer
dataChannel.send(val);
msgInput.value = "";
});现在运行代码.您应该能够使用两个浏览器选项卡登录服务器.然后，您可以设置与其他用户的对等连接，并通过单击"挂断"按钮向他发送消息并关闭数据通道.
以下是整个 client.js 文件 :
//our username
var name;
var connectedUser;
//connecting to our signaling server
var conn = new WebSocket('ws://localhost:9090');
conn.onopen = function () {
console.log("Connected to the signaling server");
};
//when we got a message from a signaling server
conn.onmessage = function (msg) {
console.log("Got message", msg.data);
var data = JSON.parse(msg.data);
switch(data.type) {
case "login":
handleLogin(data.success);
break;
//when somebody wants to call us
case "offer":
handleOffer(data.offer, data.name);
break;
case "answer":
handleAnswer(data.answer);
break;
//when a remote peer sends an ice candidate to us
case "candidate":
handleCandidate(data.candidate);
break;
case "leave":
handleLeave();
break;
default:
break;
}
};
conn.onerror = function (err) {
console.log("Got error", err);
};
//alias for sending JSON encoded messages
function send(message) {
//attach the other peer username to our messages
if (connectedUser) {
message.name = connectedUser;
}
conn.send(JSON.stringify(message));
};
//******
//UI selectors block
//******
var loginPage = document.querySelector('#loginPage');
var usernameInput = document.querySelector('#usernameInput');
var loginBtn = document.querySelector('#loginBtn');
var callPage = document.querySelector('#callPage');
var callToUsernameInput = document.querySelector('#callToUsernameInput');
var callBtn = document.querySelector('#callBtn');
var hangUpBtn = document.querySelector('#hangUpBtn');
var msgInput = document.querySelector('#msgInput');
var sendMsgBtn = document.querySelector('#sendMsgBtn');
var chatArea = document.querySelector('#chatarea');
var yourConn;
var dataChannel;
callPage.style.display = "none";
// Login when the user clicks the button
loginBtn.addEventListener("click", function (event) {
name = usernameInput.value;
if (name.length > 0) {
send({
type: "login",
name: name
});
}
});
function handleLogin(success) {
if (success === false) {
alert("Ooops...try a different username");
} else {
loginPage.style.display = "none";
callPage.style.display = "block";
//**********************
//Starting a peer connection
//**********************
//using Google public stun server
var configuration = {
"iceServers": [{ "url": "stun:stun2.1.google.com:19302" }]
};
yourConn = new webkitRTCPeerConnection(configuration, {optional: [{RtpDataChannels: true}]});
// Setup ice handling
yourConn.onicecandidate = function (event) {
if (event.candidate) {
send({
type: "candidate",
candidate: event.candidate
});
}
};
//creating data channel
dataChannel = yourConn.createDataChannel("channel1", {reliable:true});
dataChannel.onerror = function (error) {
console.log("Ooops...error:", error);
};
//when we receive a message from the other peer, display it on the screen
dataChannel.onmessage = function (event) {
chatArea.innerHTML += connectedUser + ": " + event.data + "<br />";
};
dataChannel.onclose = function () {
console.log("data channel is closed");
};
}
};
//initiating a call
callBtn.addEventListener("click", function () {
var callToUsername = callToUsernameInput.value;
if (callToUsername.length > 0) {
connectedUser = callToUsername;
// create an offer
yourConn.createOffer(function (offer) {
send({
type: "offer",
offer: offer
});
yourConn.setLocalDescription(offer);
}, function (error) {
alert("Error when creating an offer");
});
}
});
//when somebody sends us an offer
function handleOffer(offer, name) {
connectedUser = name;
yourConn.setRemoteDescription(new RTCSessionDescription(offer));
//create an answer to an offer
yourConn.createAnswer(function (answer) {
yourConn.setLocalDescription(answer);
send({
type: "answer",
answer: answer
});
}, function (error) {
alert("Error when creating an answer");
});
};
//when we got an answer from a remote user
function handleAnswer(answer) {
yourConn.setRemoteDescription(new RTCSessionDescription(answer));
};
//when we got an ice candidate from a remote user
function handleCandidate(candidate) {
yourConn.addIceCandidate(new RTCIceCandidate(candidate));
};
//hang up
hangUpBtn.addEventListener("click", function () {
send({
type: "leave"
});
handleLeave();
});
function handleLeave() {
connectedUser = null;
yourConn.close();
yourConn.onicecandidate = null;
};
//when user clicks the "send message" button
sendMsgBtn.addEventListener("click", function (event) {
var val = msgInput.value;
chatArea.innerHTML += name + ": " + val + "<br />";
//sending a message to a connected peer
dataChannel.send(val);
msgInput.value = "";
});
