HTML5的TCP和UDP Web Socket API草案定稿

这是在Web上实现UDP/TCP API的草案，沿未形成标准。该标准的一大亮点就是使用内置Promise设计模式，替代了传统JavaScript中的事件触发回调。不过各大浏览器厂商会不会这样实现还要打一个问号，毕竟编写标准的学院派和实现标准的行业派很难达到完全统一。

以下内容来自： http://www.w3.org/TR/2014/WD-tcp-udp-sockets-20141202/

接口标准提供对原始UDP套接字(Socket)，TCP客户端套接字和TCP服务器套接字API的定义。

这部分沿未形成规范。您可以使用该API来发送和接收数据，并使用TCP或UDP网络。

一个UDP的例子：

// 
// This example shows a simple implementation of UPnP-SSDP M-SEARCH
// discovery using a multicast UDPSocket 
//
      
var address = '239.255.255.250',
    port = '1900',
    serviceType = 'upnp:rootdevice',
    rn = '\r\n',
    search = '';

//  Create a new UDP client socket
var mySocket = new UDPSocket();

// Build an SSDP M-SEARCH multicast message
search += 'M-SEARCH * HTTP/1.1' + rn;
search += 'ST: ' + serviceType + rn;
search += 'MAN: "ssdp:discover"' + rn;
search += 'HOST: ' + address + ':' + port + rn;
search += 'MX: 10';


// Receive and log SSDP M-SEARCH response messages
function receiveMSearchResponses() {         

  // While data in buffer, read and log UDP message
  while (mySocket.readable.state === "readable") {            
    var msg = mySocket.readable.read();
    console.log ('Remote address: ' + msg.remoteAddress + 
                 ' Remote port: ' + msg.remotePort + 
                 'Message: ' + ab2str(msg.data)); 
      // ArrayBuffer to string conversion could also be done by piping 
      // through a transform stream. To be updated when the Streams API
      // specification has been stabilized on this point. 
  }  
      
  // Wait for SSDP M-SEARCH responses to arrive     
  mySocket.readable.wait().then(
    receiveMSearchResponses,          
    e => console.error("Receiving error: ", e);
  );     
}

// Join SSDP multicast group
mySocket.joinMulticast(address);

// Send SSDP M-SEARCH multicast message
mySocket.writeable.write(
  {data : str2ab(search),
   remoteAddress : address,
   remotePort : port
  }).then(
    () => {
      // Data sent sucessfully, wait for response
      console.log('M-SEARCH Sent');
      receiveMSearchResponses();
    },
    e => console.error("Sending error: ", e);
);

// Log result of UDP socket setup. 
mySocket.opened.then(
  () => {
    console.log("UDP socket created sucessfully");
  },
  e =>console.error("UDP socket setup failed due to error: ", e);
);

// Handle UDP socket closed, either as a result of the application 
// calling mySocket.close() or an error causing the socket to be 
   closed.
mySocket.closed.then(
  () => {
     console.log("Socket has been cleanly closed");
  },
  e => console.error("Socket closed due to error: ", e);
);

相比UDP，TCP的示例代码显得简单一些

// 
// This example shows a simple TCP echo client. 
// The client will send "Hello World" to the server on port 6789 and log 
// what has been received from the server.
//   

//  Create a new TCP client socket and connect to remote host     
var mySocket = new TCPSocket("127.0.0.1", 6789);

// Send data to server
mySocket.writeable.write("Hello World").then(
    () => {
        
        // Data sent sucessfully, wait for response
        console.log("Data has been sent to server");
        mySocket.readable.wait().then(
            () => {
            
                // Data in buffer, read it
                console.log("Data received from server:" + mySocket.readable.read());

                // Close the TCP connection
                mySocket.close();
            },
             
            e => console.error("Receiving error: ", e);
        );
    },
    e => console.error("Sending error: ", e);
);

// Signal that we won't be writing any more and can close the write half of the connection.
mySocket.halfClose();

// Log result of TCP connection attempt. 
mySocket.opened.then(
  () => {
    console.log("TCP connection established sucessfully");
  },
  e =>console.error("TCP connection setup failed due to error: ", e);
);

// Handle TCP connection closed, either as a result of the application 
// calling mySocket.close() or the other side closed the TCP  
// connection or an error causing the TCP connection to be closed.
mySocket.closed.then(
  () => {
     console.log("TCP socket has been cleanly closed");
  },
  e => console.error("TCP socket closed due to error: ", e);
);