WebRTC - 发送消息

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。