发送类

package top.ltyzqhh.Net;

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

public class TalkSend implements Runnable {
    DatagramSocket socket = null;
    BufferedReader reader = null;
    private int fromPort;
    private String toIP;
    private int toPort;

    public TalkSend(int fromPort, String toIP, int toPort) {
        this.fromPort = fromPort;
        this.toIP = toIP;
        this.toPort = toPort;

        try {
            this.socket = new DatagramSocket(fromPort);
            this.reader = new BufferedReader(new InputStreamReader(System.in));
        } catch (Exception var5) {
            var5.printStackTrace();
        }

    }

    public void run() {
        while(true) {
            String data = null;

            try {
                data = this.reader.readLine();
                byte[] bytes = data.getBytes();
                DatagramPacket packet = new DatagramPacket(bytes, 0, bytes.length, new InetSocketAddress(this.toIP, this.toPort));
                this.socket.send(packet);
                if (!data.equals("bye")) {
                    continue;
                }
            } catch (IOException var4) {
                var4.printStackTrace();
                continue;
            }

            this.socket.close();
            return;
        }
    }
}

接收类

package top.ltyzqhh.Net;

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

public class TalkReceive implements Runnable{
    DatagramSocket socket=null;
    private int port;
    private  String msgFrom;

    TalkReceive(int port, String msgFrom)
    {
        this.port=port;
        this.msgFrom=msgFrom;
        try {
            socket =new DatagramSocket(port);
        } catch (SocketException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void run() {

        while(true)
        {
            try {
                //准备接收包裹
                byte[] container = new byte[1024];
                DatagramPacket packet = new DatagramPacket(container,0,container.length);
                socket.receive(packet);//阻塞式接受包裹
                //断开连接
                byte[] data =packet.getData();
                String Receivedata = new String(data, 0, data.length);

                System.out.println(msgFrom+":"+Receivedata);

                if (Receivedata.equals("bye"))
                {
                    break;
                }
            } catch (IOException e) {
                e.printStackTrace();
            }

        }

        socket.close();
    }
    }

学生

package top.ltyzqhh.Net;

public class TalkStudent {
    public static void main(String[] args) {
        //开启两个线程
        new Thread(new TalkSend(7777,"localhost",9999)).start();
        new Thread(new TalkReceive(8888,"老师")).start();
    }
}

老师

package top.ltyzqhh.Net;

public class TalkTeacher {
    public static void main(String[] args) {
        new Thread(new TalkSend(5555,"localhost",8888)).start();
        new Thread(new TalkReceive(9999,"学生")).start();
    }
}