新增nodejs/net

Author: ruanyf

index.md

@@ -138,8 +138,9 @@ modifiedOn: 2014-05-18
 - [Events模块](nodejs/events.html)
 - [Stream接口](nodejs/stream.html)
 - [Child Process模块](nodejs/child-process.html)
-- [OS模块](nodejs/os.html)
 - [Cluster模块](nodejs/cluster.html)
+- [OS模块](nodejs/os.html)
+- [Net模块和DNS模块](nodejs/net.html)
 - [Express框架](nodejs/express.html)
 
 {% comment %}

nodejs/net.md

@@ -0,0 +1,111 @@
+---
+title: Net模块和DNS模块
+layout: page
+category: nodejs
+date: 2015-03-17
+modifiedOn: 2015-03-17
+---
+
+net模块用于底层的网络通信。
+
+## 服务器端Socket接口
+
+下面代码打开一个服务器端Socket接口，用来接受客户端的数据。
+
+```javascript
+
+var serverPort = 9099;
+var net = require('net');
+var server = net.createServer(function(client) {
+  console.log('client connected');
+  console.log('client IP Address: ' + client.remoteAddress);
+  console.log('is IPv6: ' + net.isIPv6(client.remoteAddress));
+  console.log('total server connections: ' + server.connections);
+
+  // Waiting for data from the client.
+  client.on('data', function(data) {
+    console.log('received data: ' + data.toString());
+
+    // Write data to the client socket.
+    client.write('hello from server');
+  });
+
+  // Closed socket event from the client.
+  client.on('end', function() {
+    console.log('client disconnected');
+  });
+});
+
+server.on('error',function(err){
+  console.log(err);
+  server.close();
+});
+
+server.listen(serverPort, function() {
+  console.log('server started on port ' + serverPort);
+});
+
+```
+
+上面代码中，createServer方法建立了一个服务端，一旦收到客户端发送的数据，就发出回应，同时还监听客户端是否中断通信。最后，listen方法打开服务端。
+
+## 客户端Socket接口
+
+
+客户端Socket接口用来向服务器发送数据。
+
+```javascript
+
+var serverPort = 9099;
+var server = 'localhost';
+var net = require('net');
+
+console.log('connecting to server...');
+var client = net.connect({server:server,port:serverPort},function(){
+  console.log('client connected');
+
+  // send data
+  console.log('send data to server');
+  client.write('greeting from client socket');
+});
+
+client.on('data', function(data) {
+  console.log('received data: ' + data.toString());
+  client.end();
+});
+
+client.on('error',function(err){
+  console.log(err);
+});
+client.on('end', function() {
+  console.log('client disconnected');
+});
+
+```
+
+上面代码连接服务器之后，就向服务器发送数据，然后监听服务器返回的数据。
+
+## DNS模块
+
+DNS模块用于解析域名。resolve4方法用于IPv4环境，resolve6方法用于IPv6环境，lookup方法在以上两种环境都可以使用，返回IP地址（address）和当前环境（IPv4或IPv6）。
+
+```javascript
+
+var dns = require('dns');
+
+dns.resolve4('www.pecollege.net', function (err, addresses) {
+  if (err)
+    console.log(err);
+
+  console.log('addresses: ' + JSON.stringify(addresses));
+});
+
+dns.lookup('www.pecollege.net', function (err, address, family) {
+  if (err)
+    console.log(err);
+
+  console.log('addresses: ' + JSON.stringify(address));
+  console.log('family: ' + JSON.stringify(family));
+});
+
+```