发送端：

package chat;

import java.io.BufferedReader;

import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;


public class UDPSenderDemo1 {
    public static void main(String[] args) throws Exception {

        DatagramSocket socket=new DatagramSocket(8888);

        //准备数据，控制台读取System.in
        BufferedReader reader=new BufferedReader(new InputStreamReader(System.in));

        while(true){
            String data=reader.readLine();
            byte[] bytes=data.getBytes();
            DatagramPacket packet=new DatagramPacket(bytes,0,bytes.length,new InetSocketAddress("127.0.0.1",9090));

            socket.send(packet);
            if (data.equals("bye")){
                break;
            }
        }

        socket.close();

    }
}

接收端：

package chat;

import java.net.DatagramPacket;
import java.net.DatagramSocket;


public class UDPRecieverDemo1 {
    public static void main(String[] args) throws Exception {

        DatagramSocket socket=new DatagramSocket(9090);

        while(true){

            //准备接收包裹
            byte[] container=new byte[1024];
            DatagramPacket packet=new DatagramPacket(container,0,container.length);
            socket.receive(packet);//阻塞式接收包裹

            //断开连接
            byte[] data=packet.getData();
            String recieveData=new String(data,0,packet.getLength());

            System.out.println(recieveData);

            if (recieveData.equals("bye")){
                break;
            }


        }

        socket.close();
    }
}

UDP聊天实现