UDP發送消息（Java）

import java.io.IOException;
import java.net.*;
import java.util.Scanner;

/**
 * Created by Administrator on 2020/6/30.
 */
public class day04 {
    public static void main(String[] args){
        new Receive().start();
        new Send().start();
    }
}

class Receive extends Thread{
    public void run(){
        DatagramSocket socket = null;
        try {
            socket = new DatagramSocket(6666);
        } catch (SocketException e) {
            e.printStackTrace();
        }
        DatagramPacket packet = new DatagramPacket(new byte[1024],1024);
        while (true){
            try {
                socket.receive(packet);  // 接貨
            } catch (IOException e) {
                e.printStackTrace();
            }
            byte[] arr=packet.getData();
            int len=packet.getLength();
            String ip = packet.getAddress().getHostAddress();
            int port = packet.getPort();
            System.out.println(ip+":"+port+":"+new String(arr,0,len));
        }
    }

}

class Send extends Thread{
    public void run(){
        Scanner sc = new Scanner(System.in);
        DatagramSocket socket = null;   //創建碼頭
        try {
            socket = new DatagramSocket();
        } catch (SocketException e) {
            e.printStackTrace();
        }
        while (true){
            String str = sc.nextLine();
            if("quit".equals(str)){
                break;
            }
            DatagramPacket packet = null;
            try {
                packet = new DatagramPacket(str.getBytes(),str.getBytes().length, InetAddress.getByName("127.0.0.1"),6666);
            } catch (UnknownHostException e) {
                e.printStackTrace();
            }
            try {
                socket.send(packet);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        socket.close();
    }
}