java网络编程

Java中网络编程离不开java.net包,其中常用的类有

InetAddress  和 SocketImpl
Socket、ServerSocket //TCP编程
DatagramPacket 和 DatagramSocket//UDP编程
URL、URLConnection 和 URLEncoder

1. 什么是socket: 操作系统中用于网络通信的端点.
   黄色为网卡驱动程序
   

2. InetAddress:
   封装 IP 地址和 DNS
   示例(运行时记得联网!):

    import java.net.InetAddress;
    import java.net.UnknownHostException;
    public class Test1 {
   
    public static void main(String[] args) {
    	try {
    		InetAddress a1 = InetAddress.getByName("www.sina.com");
    		InetAddress a2 = InetAddress.getByName("127.0.0.1");
    		
    		System.out.println(a1.getHostAddress());
    		System.out.println(a2.getHostName());
    	} catch (UnknownHostException e) {
    		// TODO Auto-generated catch block
    		e.printStackTrace();
    	}
    }
    }
   

3. ServerSocket
   用来创建套接字(TCP)服务器
   accept( ) 方法用于接收客户端的请求并返回连接到客户端的套接字(Socket),此方法是个阻塞方法

4. Socket
   用来创建客户端套接字
   构造函数
   Socket(String hostName, int port)
   Socket(InetAddress a, int port)
   常用方法
   InetAddress getInetAddress( )
   int getPort( )//得到远程port
   int getLocalPort( )//得到本地port
   示例(先运行T1在T2):
   T1类:

    import java.io.BufferedReader;
    import java.io.BufferedWriter;
    import java.io.IOException;
    import java.io.InputStreamReader;
    import java.io.OutputStreamWriter;
    import java.net.ServerSocket;
    import java.net.Socket;
    public class T1 {
    	public static void main(String[] args) {
    		ServerSocket ss = null;
    		Socket s = null;
    		BufferedReader reader = null;
    		BufferedWriter writer = null;
    		try {
    			ss = new ServerSocket(10088);	
    			s = ss.accept();
    			reader = new BufferedReader(new InputStreamReader(s.getInputStream()));	
    			String info = null;
    			while(true) {
    				info = reader.readLine();
    				System.out.println(info);
    				if("再见！".equals(info)) {
    					break;
    				}
    			}
    			writer = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
    			writer.write("你好，！\n");
    			writer.flush();
    			writer.write("欢迎你学习软件开发！\n");
    			writer.flush();
    			writer.write("谢谢！\n");
    			writer.flush();
    			writer.write("再见！\n");
    			writer.flush();	
    			System.out.println(s.getLocalPort());
    			System.out.println(s.getPort());
    		} catch (IOException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    	}
    }
   

T2类:

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.net.UnknownHostException;
public class T2 {
	public static void main(String[] args) {
		Socket s = null;
		BufferedReader reader = null;
		BufferedWriter writer = null;
		try {
			s = new Socket("127.0.0.1", 10088);
			writer = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
			writer.write("你好\n");
			writer.flush();
			writer.write("我想学习软件开发！\n");
			writer.flush();
			writer.write("谢谢！\n");
			writer.flush();
			writer.write("再见！\n");
			writer.flush();
			reader = new BufferedReader(new InputStreamReader(s.getInputStream()));	
			String info = null;
			while(true) {
				info = reader.readLine();
				System.out.println(info);
				if("再见！".equals(info)) {
					break;
				}
			}	
			System.out.println(s.getLocalPort());
			System.out.println(s.getPort());
		} catch (UnknownHostException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

5. 数据报
   单向的,不连续的,不可靠的数据包,其中有2个对象.
   DatagramPacket(相当于邮包) DatagramSocket(相当于邮递员)假设每个人都拥有自己的邮递员
   DatagramSocket
   • 用于发送或接收 DatagramPacket
   • 构造函数
   DatagramSocket()
   DatagramSocket(int port)
   • 常用方法
   void send(DatagramPacket d)
   void receive(DatagramPacket p)
   void close()
   DatagramPacket
   • 用来接收或发送数据，只能存放字节
   • 构造函数
   DatagramPacket(byte[] data, int size) 接收时使用
   DatagramPacket(byte[] data, int size, InetAddress I,
   int port) 发送时使用， InetAddress为远程地
   址，port为远程端口
   • 常用方法
   byte[] getData() 返回数据缓冲区
   int getLength() 返回将要发送或接收到的数据的长度
   示例:
   T1类:(用于收)

    import java.io.IOException;
     import java.net.DatagramPacket;
     import java.net.DatagramSocket;
    import java.net.SocketException;
   
     public class T1 {
   
    public static void main(String[] args) {
    	DatagramSocket socket = null;
    	DatagramPacket packet = null;
    	try {
    		socket = new DatagramSocket(10011);//邮递员通过此端口收进来,相当于收货人地址
    		byte[] pool = new byte[1024];
    		packet = new DatagramPacket(pool, 0, pool.length);
    		socket.receive(packet);
    		String info = new String(packet.getData());
    		System.out.println("T1收到了数据：" + info);
    	} catch (SocketException e) {
    		// TODO Auto-generated catch block
    		e.printStackTrace();
    	} catch (IOException e) {
    		// TODO Auto-generated catch block
    		e.printStackTrace();
    	}	
    	}
     }
   

T2类:(用于发信息)

	import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;

public class T2 {

	public static void main(String[] args) {
		DatagramSocket socket = null;
		DatagramPacket packet = null;
		
		try {
			socket = new DatagramSocket(10022);
			
			byte[] pool = new byte[1024];
			packet = new DatagramPacket(pool, 0, pool.length, InetAddress.getByName("127.0.0.1"), 10011);
			packet.setData("我是T2".getBytes());
			
			socket.send(packet);
			
		} catch (SocketException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (UnknownHostException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}