java UDP實作一個聊天工具

題目：
假設Tom和Jerry利用Java UDP進行聊天，請為他們撰寫程式，具體如下：
（1）、Tom和Jerry聊天的雙方都應該具有發送端和接收端；
（2）、利用DatagramSocket與DatagramPacket；
（3）、實作 java.lang.Runnable類，重寫 run()方法，

學過計網的都知道，利用三元組（ip地址，協議，埠）就可以標識網路的行程了，
而進行通信我們直接運用socket就可以了，首先需要知道是socket是什么，這部分可以參考這個大佬寫的博客，
https://blog.csdn.net/pashanhu6402/article/details/96428887
實作一個客戶端，那么需要Tom和Jerry都可以實作接收和發送功能，分別用兩個執行緒啟動，

接收執行緒Receive_Thread.java

package Chat_UDP;

import java.io.IOException;
import java.util.Date;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.text.SimpleDateFormat;

public class Receive_Thread extends Thread {
    private static final int MAX_RECEIVE_BUFFER = 1024;
    private DatagramSocket server;
    private DatagramPacket packet;
    byte[] buffer = new byte[MAX_RECEIVE_BUFFER];
    
    public Receive_Thread(DatagramSocket server)
    {
        this.server = server;
        packet = new DatagramPacket(buffer, buffer.length);
    }
    
    @Override
    public void run() {
        try
        {
            while(true)
            {
                //接收資料包
                server.receive(packet);
                String s = new String(packet.getData(),packet.getOffset(),packet.getLength(),"UTF-8");
                Date day=new Date();    
                SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");   
                if(packet.getPort() == 10001)
                	System.out.println("Tom"+packet.getAddress()+"  說:"+s+"\t"+df.format(day));
                else{
                	System.out.println("Jerry"+packet.getAddress()+" 說 :"+s+"\t"+df.format(day));
                }
                packet.setLength(buffer.length);
            }
        }
        catch(IOException e)
        {
            System.out.println("IOException");
        }
    }
}

發送執行緒Send_Thread.java

package Chat_UDP;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.util.Scanner;

public class Send_Thread extends Thread{
    //發送的socket端
    private DatagramSocket sender = null;
    //待發送的目標地址
    private InetSocketAddress address = null;
    //從鍵盤輸入
    Scanner scan = new Scanner(System.in);
    public Send_Thread(DatagramSocket sender,InetSocketAddress address)
    {
        this.sender = sender;
        this.address = address;
    }
    
    @Override
    public void run() {
        // TODO Auto-generated method stub
        try
        {
            while(true)
            {
                //輸入待發送的內容
                String input = scan.nextLine();
                if(input.equals("exit"))
                    break;
                byte[] data = null;
                data = input.getBytes("UTF-8");
                //創建UDP資料報
                DatagramPacket pack = new DatagramPacket(data, data.length,address);
                sender.send(pack);    
            }
            System.out.println("Exit!");
            
        }catch(IOException e)
        {
            System.out.println("IOException");
        }
    }

}

聊天服務器
Chat_Server.java

package Chat_UDP;
//楊麗冰 201831064402
import java.net.DatagramSocket;
import java.net.InetSocketAddress;

public class Chat_Server {

    private static final int DEST_PORT = 8888;
    private static final int SEND_PORT = 10001;
    private static final int RECE_PORT = 9000;
    private static final String IP = "127.0.0.1";

    public static void main(String[] args)
    {
        try{
            Send_Thread send_thread = null;
            Receive_Thread rece_thread = null;
            InetSocketAddress address = null;
            //創建待接受資料包的目的機的埠號和IP地址
            address = new InetSocketAddress(IP, DEST_PORT);
            //創建發送的Socket端
            DatagramSocket sendsocket = new DatagramSocket(SEND_PORT);
            //創建接受的Socket端
            DatagramSocket recesocket = new DatagramSocket(RECE_PORT);
            //發送執行緒建立
            send_thread = new Send_Thread(sendsocket, address);
            //接受執行緒的建立
            rece_thread = new Receive_Thread(recesocket);
            send_thread.start();
            rece_thread.start();
        }catch(Exception e)
        {
            System.out.println("Exception!");
        }

    }

}

聊天客戶端 Chat_Client.java

package Chat_UDP;
//楊麗冰 201831064402
import java.net.DatagramSocket;
import java.net.InetSocketAddress;

public class Chat_Client {
	//宣告埠號
    private static final int DEST_PORT = 9000;
    private static final int SEND_PORT = 10000;
    private static final int RECE_PORT = 8888;
    private static final String IP = "127.0.0.1";

    public static void main(String[] args)
    {
        try{
            Send_Thread send_thread = null;
            Receive_Thread rece_thread = null;
            InetSocketAddress address = null;
            //創建待接受資料包的目的機的埠號和IP地址
            address = new InetSocketAddress(IP, DEST_PORT);
            //創建發送的Socket端
            DatagramSocket sendsocket = new DatagramSocket(SEND_PORT);
            //創建接受的Socket端
            DatagramSocket recesocket = new DatagramSocket(RECE_PORT);
            //發送執行緒建立
            send_thread = new Send_Thread(sendsocket, address);
            //接受執行緒的建立
            rece_thread = new Receive_Thread(recesocket);
            send_thread.start();
            rece_thread.start();

        }catch(Exception e)
        {
            System.out.println("Exception!");
        }

    }


}