require('net').createServer(function(socket) {
   // new connection
   socket.on('data', function(data) {
     // got data
   });
   socket.on('end', function(data) {
     // connection closed
   });
   socket.write('Some string');
 }).listen();

var server = require('net').createServer();
 var port = ;
 server.on('listening', function() {
   console.log('Server is listening on port', port);
 });
 server.on('connection', function(socket) {
   console.log('Server has a new connection');
   socket.end();
   server.close();
 });
 server.on('close', function() {
   console.log('Server is now closed');
 });
 server.on('error', function(err) {
   console.log('Error occurred:', err.message);
 });
 server.listen(port);

 var server = require('net').createServer(function(socket) {
   console.log('new connection');
   socket.setEncoding('utf');
   socket.write("Hello! You can start typing. Type 'quit' to exit.\n");
   socket.on('data', function(data) {
     console.log('got:', data.toString())
     if (data.trim().toLowerCase() === 'quit') {
       socket.write('Bye bye!');
       return socket.end();
     }
     //反馈回客户端
     socket.write(data);
   });
   socket.on('end', function() {
     console.log('Client connection ended');
   });
 }).listen();

 var ws = require('fs').createWriteStream('helloworld.txt');
 require('net').createServer(function(socket) {
   socket.pipe(ws);
 }).listen();

 require('net').createServer(function(socket) {
   var rs = require('fs').createReadStream('hello.txt');
   rs.pipe(socket);
 }).listen();

 var timeout = ; // minute
 socket.setTimeout(timeout);
 socket.on('timeout', function() {
   socket.write('idle timeout, disconnecting, bye!');
   socket.end();
 });

 socket.setTimeout(60000, function() {
   socket.end('idle timeout, disconnecting, bye!');
 });

var net = require('net');
 var server = net.createServer();
 var sockets = [];
 server.on('connection', function(socket) {
   console.log('got a new connection');
   sockets.push(socket);
   console.log('sockets length:', sockets.length);
   socket.on('data', function(data) {
     console.log('got data:', data.toString());
     sockets.forEach(function(otherSocket) {
       if (otherSocket !== socket) {
         otherSocket.write(data);
       }
     });
   });
   socket.on('close', function() {
     console.log('connection closed');
     var index = sockets.indexOf(socket);
     sockets.splice(index, );
     console.log('sockets length:', sockets.length);
   });
 });
 server.on('error', function(err) {
   console.log('Server error:', err.message);
 });
 server.on('close', function() {
   console.log('Server closed');
 });
 server.listen();