Java学习笔记52（网络编程：UDP协议案例）

InetAddress类：

表示互联网中的IP地址，示例：

package demo;import java.net.InetAddress;import java.net.UnknownHostException;public class InetAddressDemo {    public static void main(String[] args) throws UnknownHostException {        function1();        function2();    }    public static void function1() throws UnknownHostException {        InetAddress inet = InetAddress.getLocalHost();        System.out.println(inet.getHostName());// 获取主机名        // 输出:DESKTOP-Q3O8AEO        System.out.println(inet.getHostAddress());// 获取主机IP        // 输出:192.168.87.1    }    public static void function2() throws UnknownHostException {        // 获得其他IP        InetAddress inet = InetAddress.getByName("www.baidu.com");        System.out.println(inet);        // 输出:www.baidu.com/111.13.100.92    }}

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UDP协议：无连接通信协议，最大64KB，不安全

TCP协议：面向连接通信协议，可靠安全，三次握手以确认连接，相对速度慢，适合大数据传输

UDP示例:

发送端：

package demo;import java.io.IOException;import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.InetAddress;public class UDPSend {    public static void main(String[] args) {        try {            byte[] data = "你好".getBytes();            InetAddress inet = InetAddress.getByName("127.0.0.1");            DatagramPacket dp = new DatagramPacket(data, data.length, inet, 6000);            DatagramSocket ds = new DatagramSocket();            ds.send(dp);            ds.close();        } catch (IOException ex) {            System.out.println(ex);        }    }}

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接收端：

package demo;import java.io.IOException;import java.net.DatagramPacket;import java.net.DatagramSocket;public class UDPReceive {    public static void main(String[] args) {        try {            DatagramSocket ds = new DatagramSocket(6000);            byte[] data = new byte[1024];            DatagramPacket dp = new DatagramPacket(data, data.length);            ds.receive(dp);            int length = dp.getLength();            String ip = dp.getAddress().getHostAddress();            System.out.println(ip + ":" + new String(data, 0, length));            ds.close();        } catch (IOException ex) {            System.out.println(ex);        }    }}

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先运行接收端，再运行发送端，结果：

输出：127.0.0.1:你好

功能可以提升，实现键盘输入的聊天：

发送端：

package demo;import java.io.IOException;import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.InetAddress;import java.util.Scanner;public class UDPSend {    public static void main(String[] args) {        try {            Scanner sc = new Scanner(System.in);            DatagramSocket ds = new DatagramSocket();            InetAddress inet = InetAddress.getByName("127.0.0.1");            while (true) {                String message = sc.nextLine();                byte[] data = message.getBytes();                DatagramPacket dp = new DatagramPacket(data, data.length, inet, 7000);                ds.send(dp);            }        } catch (IOException ex) {            System.out.println(ex);        }    }}

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接收端：

package demo;import java.io.IOException;import java.net.DatagramPacket;import java.net.DatagramSocket;public class UDPReceive {    public static void main(String[] args) {        try {            DatagramSocket ds = new DatagramSocket(7000);            byte[] data = new byte[1024];            while (true) {                DatagramPacket dp = new DatagramPacket(data, data.length);                ds.receive(dp);                int length = dp.getLength();                String ip = dp.getAddress().getHostAddress();                System.out.println(ip + ":" + new String(data, 0, length));            }        } catch (IOException ex) {            System.out.println(ex);        }    }}

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先后运行，在发送端发送的消息可以随时在接收端收到，这里就实现了一个简单的聊天功能

同个局域网下的多台电脑之间也可以聊天，只要修改成相应的IP地址即可

辽远或偏僻的地方，而会常常想起这一次的旅行，