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。

　　简介

　　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。

　　使用此 API 的部分用例：

• 能够与 SMTP, POP3 和 IMAP 服务器进行通信的邮件服务器。
• 一个能与 IRC 服务器进行通信的 IRC 客户端 （注* IRC 是一种通过网络的即时聊天方式。其主要用于群组聊天。）
• 实现一个 SSH 应用程序
• 与现有的消费硬件产品进行通信，如互联网电视
• 游戏服务器
• 端到端应用程序（注* P2P 或对等网络应用）
• 本地网络多播服务（multicast service）发掘，例如 UPnP/ SSDP 和 mDNS

　　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);
);