nodejs 如何使用upgrade，并且C/B 发送消息

 1 const http = require('http');
 const querystring = require("querystring");
 var postData = querystring.stringify({
     'msg': 'Hello World!'
 });
 // Create an HTTP server
 var srv = http.createServer((req, res) => {
     res.writeHead(200, {'Content-Type': 'text/plain'});
     res.end('okay');
 });
 srv.on('upgrade', (req, socket, head) => {

     socket.write('HTTP/1.1 101 Web Socket Protocol Handshake\r\n' +
         'Upgrade: WebSocket\r\n' +
         'Connection: Upgrade\r\n' +
         '\r\n');

     socket.on("data", (d)=> {
         console.log(d.toString())
     });
     socket.on("end", ()=> {
         socket.write("发送服务器的消息");
         socket.end();
         if (!socket.destroyed) {
             console.log(" socket.end 会销毁socket,不信你可以执行end，看会不会进入这个方法")
             if (socket.destroy) {
                 socket.destroy();
                 console.log(!socket.destroyed)
             }

         }
     });
 });

 // now that server is running
 srv.listen(1337, '127.0.0.1', () => {

     // make a request
     var options = {
         port: 1337,
         hostname: '127.0.0.1',
         headers: {
             'Connection': 'Upgrade',
             'Upgrade': 'websocket'
         }
     };

     var req = http.request(options);
     req.on('upgrade', (res, socket, upgradeHead) => {
         socket.write('发送客户端的消息\r\n');
         socket.end();

         socket.on('data', (chunk) => {
             console.log(chunk.toString());
         });
         socket.on('end', () => {
             console.log("服务器消息接收完毕");
             console.log("socket已经被销毁",socket.destroyed)
         });

     });

     req.end();

 });

整个流程是

1 ：request的 header里加上:

 'Connection': 'Upgrade',
 'Upgrade': 'websocket'

生成的http.ClientRequest 最后一定要调用end函数，不然服务器会一直等待你消息发送完毕

2: 服务器监听 ‘Upgrade’，然后返回：

'HTTP/1.1 101 Web Socket Protocol Handshake\r\n' +
    'Upgrade: WebSocket\r\n' +
    'Connection: Upgrade\r\n' +
   '\r\n'

维基百科里说了，这样叫作握手！

这样的话，Upgrade 就算建立起来了。

3:然后就可以通过socket相互消息了。记住socket.end一旦执行，就会断开这次的tcp链接了。