import java.io.IOException;

 import java.net.DatagramPacket;

 import java.net.DatagramSocket;

 import java.net.InetAddress;

 import java.net.InetSocketAddress;

 import java.util.Scanner;

 /**

  * 聊天小程序

  * 使用UDP进行通信

  * 开一个线程，监听一个端口，接收消息

  * 这里主要用于本机通信，IP为127.0.0.1

  *

  * 发送消息正常，接收消息没反应

  * @author GXF

  *

  */

 public class ChatWindow {

     private int listenPort;                    //监听端口

     private int desPort;                    //目标端口

     /**

      * 初始化目的端口和监听端口

      * @param desPort

      * @param listenPort

      */

     public ChatWindow(int desPort, int listenPort){

         this.desPort = desPort;

         this.listenPort = listenPort;

         //启动监听线程

         Thread listenMessageThread = new Thread(new ReceiveMessage());

         listenMessageThread.start();

         System.out.println("程序已启动，愉快的开始聊天吧！");

         //接收用户输入的消息

         Scanner scanner = new Scanner(System.in);

         while(true){

             String message = scanner.nextLine();

             sendMessag(message);

         }

     }

     /**

      * 向目的端口发送一个消息

      * @param message

      */

     public void sendMessag(String message){

         //初始化一个socket

         //设置好数据包

         //发送消息

         try {

             DatagramSocket socketToSendMessage = new DatagramSocket();

             byte buff[] = message.getBytes();

             DatagramPacket packetToSend = new DatagramPacket(buff, buff.length, InetAddress.getByName("127.0.0.1"), desPort);

             socketToSendMessage.send(packetToSend);                                         //发送消息

             socketToSendMessage.close();                                                    //关闭socket

         } catch (Exception e) {

             e.printStackTrace();

         }

     }

     /**

      * 监听端口线程

      * 实例化一个DatagramSocket，并绑定一个端口进行监听

      * @author GXF

      *

      */

     class ReceiveMessage implements Runnable{

         private DatagramSocket listenSocket;

         private DatagramPacket receivePacket;

         private byte buff[] = new byte[1024];

         @Override

         public void run() {

             //init

             init();

             //start 监听

             while(true){

                 try {

                     listenSocket.receive(receivePacket);                    //接收数据包

                     String receiveMessage = new String(receivePacket.getData(), 0, receivePacket.getLength());

                     System.out.println(receiveMessage);                        //输出接收到的消息

                 } catch (IOException e) {

                     e.printStackTrace();

                 }

             }

         }

         /**

          * 对socket，端口,进行初始化

          */

         public void init(){

             try {

                 InetSocketAddress serverSocketAddress = new InetSocketAddress(listenPort);

                 listenSocket = new DatagramSocket(serverSocketAddress);

                 receivePacket = new DatagramPacket(buff, buff.length);

             } catch (Exception e) {

                 e.printStackTrace();

             }

         }

     }

     public static void main(String[] args) {

         if(args.length != 2)

         {

             System.out.println("usage: java ChatWindow desport listenport");

             return;

         }

         int desport = Integer.valueOf(args[0]);

         int listenPort = Integer.valueOf(args[1]);

         //first is desport, seconde is listenport

         ChatWindow chatWindow = new ChatWindow(desport, listenPort);

     }

 }