发送端

package com;

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

public class TalkSend implements Runnable {
    private DatagramSocket client;
    private BufferedReader br;
    private InetSocketAddress address;

    public TalkSend(int port, InetSocketAddress address) {
        try {
            this.client = new DatagramSocket(port);
            br = new BufferedReader(new InputStreamReader(System.in));
            this.address = address;
        } catch (SocketException e) {
        }
    }

    @Override
    public void run() {
        while (true) {
            try {
                String str = br.readLine();
                byte[] data = str.getBytes();
                DatagramPacket datagramPacket = new DatagramPacket(data, 0, data.length, this.address);
                client.send(datagramPacket);
                if (str.equals("bye")) {
                    break;
                }
            } catch (Exception e) {
            }
        }
        client.close();
        System.out.println("end");
    }
}

接收端

package com;

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

/**
 * 接收端：使用面向对象封装
 */
public class TalkReceive implements Runnable {
    private DatagramSocket server;

    public TalkReceive(int port) {
        try {
            this.server = new DatagramSocket(port);
        } catch (SocketException e) {
        }
    }

    @Override
    public void run() {
        while (true) {
            try {
                byte[] container = new byte[1024 * 60];
                DatagramPacket packet = new DatagramPacket(container, 0, container.length);
                server.receive(packet);
                byte[] data = packet.getData();
                int len = packet.getLength();
                String s = new String(data, 0, len);
                System.out.println(s);
                if (s.equals("bye")) {
                    break;
                }
            } catch (Exception e) {
            }
        }
        server.close();
        System.out.println("end");
    }
}

package com;

import java.net.InetSocketAddress;

public class TalkStudent {
    public static void main(String[] args) {
        new Thread(new TalkReceive(5555)).start();
        new Thread(new TalkSend(1111, new InetSocketAddress("127.0.0.1", 2222))).start();
    }
}

package com;

import java.net.InetSocketAddress;

public class TalkTeacher {
    public static void main(String[] args) {
        new Thread(new TalkReceive(2222)).start();
        new Thread(new TalkSend(3333, new InetSocketAddress("127.0.0.1", 5555))).start();
    }
}