DatagramSocket此类表示用来发送和接收数据报包的套接字。

DatagramPacket此类表示数据报包。

package cn.sxt.UdpDemo;

import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.InetAddress;

import java.util.Scanner;

public class ClientB {

    public static void main(String[] args) throws IOException {

        //创建一个datagram socket 用于结束

        DatagramSocket ds = new DatagramSocket(9000);

        while(true) {

            //接收客户端A的信息

            byte[] recbuf = new byte[1024];

            DatagramPacket recDp = new DatagramPacket(recbuf, recbuf.length);

            ds.receive(recDp);

            String recMsg = new String(recbuf,0,recDp.getLength());

            System.out.println("clientA说"+recMsg);

            //发送信息到客户端A

            System.out.println("请输入");

            Scanner sc = new Scanner(System.in);

            String msg = sc.next();

            System.out.println("开始发送数据："+msg);

            InetAddress toIp = InetAddress.getLocalHost();

            byte[] buf = msg.getBytes();

            // 构造数据报包，用来将长度为 length 偏移量为 offset 的包发送到指定主机上的指定端口号。

            DatagramPacket dp = new DatagramPacket(buf,buf.length,toIp,8000);

            //发送数据报

            ds.send(dp);

            //ds.close();

        }

    }

}

package cn.sxt.UdpDemo;

import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.InetAddress;

import java.util.Scanner;

public class ClientA {

    public static void main(String[] args) throws IOException {

        //创建数据报套接字并将其绑定到本地主机上的指定端口8000

        DatagramSocket ds = new DatagramSocket(8000);

        while(true) {

            System.out.println("请输入");

            Scanner sc = new Scanner(System.in);

            String msg = sc.nextLine();

            //发送信息到客户端B

            System.out.println("开始发送数据："+msg);

            byte[] buf = msg.getBytes();

            InetAddress toIp = InetAddress.getLocalHost();

            // 构造数据报包，用来将长度为 length 偏移量为 offset 的包发送到指定主机上的指定端口号。

            DatagramPacket dp = new DatagramPacket(buf,buf.length,toIp,9000);

            //用数据报包的套接字,通过8000发送数据报

            ds.send(dp);

            //接收客户端B的信息

            byte[] recBuf = new byte[1024];

            DatagramPacket recDp = new DatagramPacket(recBuf,recBuf.length);

            //信息接收

            ds.receive(recDp);

            String recMsg = new String(recBuf,0,recDp.getLength());

            System.out.println("clientB说:"+recMsg);

            //ds.close();

        }

    }

}