import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.InetAddress;

import java.net.SocketException;

import java.net.UnknownHostException;

//群聊发送端

public class ChatSender extends Thread {

    @Override

    public void run() {

        try {

            //建立udp的服务

            DatagramSocket socket = new DatagramSocket();

            //准备数据，把数据封装到数据包中发送

            BufferedReader keyReader = new BufferedReader(new InputStreamReader(System.in));

            String line = null;

            DatagramPacket packet  = null;

            while((line = keyReader.readLine())!=null){

                //把数据封装 到数据数据包中，然后发送数据。

                packet = new DatagramPacket(line.getBytes(), line.getBytes().length, InetAddress.getByName("192.168.15.255"), 9090);

                //把数据发送出去

                socket.send(packet);

            }

            //关闭 资源

            socket.close();

        } catch (IOException e) {

            e.printStackTrace();

        }

    }

}

import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.SocketException;

//群聊接收端

public class ChatReceive extends Thread {

    @Override

    public void run() {

        try {

            //建立udp的服务,要监听一个端口

            DatagramSocket socket = new DatagramSocket(9090);

            //准备空的数据包存储数据

            byte[] buf = new byte[1024];

            DatagramPacket packet = new DatagramPacket(buf, buf.length);

            boolean flag = true;

            while(flag){

                socket.receive(packet);

                // packet.getAddress() 获取对方数据 包的IP地址对象。

                System.out.println(packet.getAddress().getHostAddress()+"说:"+new String(buf,0,packet.getLength()));

            }

            //关闭资源

            socket.close();

        }catch (IOException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

    }

}

public class ChatMain {

    public static void main(String[] args) {

        ChatReceive chatReceive = new ChatReceive();

        chatReceive.start();

        ChatSender chatSender = new ChatSender();

        chatSender.start();

    }

}