13.16 Net模块和DNS模块
最后更新于：2022-04-01 05:10:03
net模块用于底层的网络通信。
[TOC]
## 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。
~~~
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。
~~~
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）。
~~~
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));
});
~~~