receive

package com.itheima.A03_updatedemo1;

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

public class ReceiveMessage {
    public static void main(String[] args) throws IOException {
        DatagramSocket ds = new DatagramSocket(10086);


        byte[] bytes = new byte[1024];
        DatagramPacket dp = new DatagramPacket(bytes, bytes.length);

        while (true) {
            ds.receive(dp);

            //3. 解析数据包
            byte[] data = dp.getData();
            int len = dp.getLength();
            String ip = dp.getAddress().getHostName();
            String name = dp.getAddress().getHostName();

            System.out.println("ip为： " + ip + " 主机名为： " + name + "的人，发送了数据：" + new String(data, 0, len));
        }


    }
}

sent

package com.itheima.A03_updatedemo1;

import javax.print.DocFlavor;
import java.io.IOException;
import java.net.*;
import java.nio.charset.StandardCharsets;
import java.util.Scanner;

public class sentMessageDemo2 {
    public static void main(String[] args) throws IOException {
        //UDP发送数据：数据来自键盘录入，直到输入的数据是886，发送数据结束
        //UDP接收数据：因为接收端不知道发送端什么时候停止发送，故采用死循环接收

        //1. 创建DatagramSocket的对象
        DatagramSocket ds = new DatagramSocket();

        //2. 打包数据
        Scanner sc = new Scanner(System.in);
        while (true) {
            System.out.println("请输入您要说的话：");
            String str = sc.nextLine();
            if (str.equals("886")) {
                break;
            }
            byte[] bytes = str.getBytes();

            InetAddress address = InetAddress.getByName("127.0.0.1");
            int port = 10086;

            DatagramPacket dp = new DatagramPacket(bytes, bytes.length, address, port);

            //3.发送数据
            ds.send(dp);
        }

        // 4. 释放资源
        ds.close();
    }
}