java UDP实现一个聊天工具的示例代码

题目：
假设Tom和Jerry利用Java UDP进行聊天，请为他们编写程序。具体如下：
（1）、Tom和Jerry聊天的双方都应该具有发送端和接收端；
（2）、利用DatagramSocket与DatagramPacket；
（3）、实现 java.lang.Runnable类，重写 run()方法。

学过计网的都知道，利用三元组（ip地址，协议，端口）就可以标识网络的进程了。
而进行通信我们直接运用socket就可以了，首先需要知道是socket是什么，这部分可以参考这个大佬写的博客。
https://www.jb51.net/article/121601.htm
实现一个客户端，那么需要Tom和Jerry都可以实现接收和发送功能，分别用两个线程启动。

接收线程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)
  {
   //接收数据包
   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()+" 说:"+s+"\t"+df.format(day));
   else{
   System.out.println("Jerry"+packet.getAddress()+" 说 :"+s+"\t"+df.format(day));
   }
   packet.setLength(buffer.length);
  }
 }
 catch(IOException e)
 {
  System.out.println("IOException");
 }
}
}

发送线程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{
//发送的socket端
private DatagramSocket sender = null;
//待发送的目标地址
private InetSocketAddress address = null;
//从键盘输入
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)
  {
   //输入待发送的内容
   String input = scan.nextLine();
   if(input.equals("exit"))
    break;
   byte[] data = null;
   data = input.getBytes("UTF-8");
   //创建UDP数据报
   DatagramPacket pack = new DatagramPacket(data, data.length,address);
   sender.send(pack);
  }
  System.out.println("Exit!");

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

}

聊天服务器
Chat_Server.java

package Chat_UDP;
//杨丽冰 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;
  //创建待接受数据包的目的机的端口号和IP地址
  address = new InetSocketAddress(IP, DEST_PORT);
  //创建发送的Socket端
  DatagramSocket sendsocket = new DatagramSocket(SEND_PORT);
  //创建接受的Socket端
  DatagramSocket recesocket = new DatagramSocket(RECE_PORT);
  //发送线程建立
  send_thread = new Send_Thread(sendsocket, address);
  //接受线程的建立
  rece_thread = new Receive_Thread(recesocket);
  send_thread.start();
  rece_thread.start();
 }catch(Exception e)
 {
  System.out.println("Exception!");
 }

}

}

聊天客户端 Chat_Client.java

package Chat_UDP;
//杨丽冰 201831064402
import java.net.DatagramSocket;
import java.net.InetSocketAddress;

public class Chat_Client {
//声明端口号
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;
  //创建待接受数据包的目的机的端口号和IP地址
  address = new InetSocketAddress(IP, DEST_PORT);
  //创建发送的Socket端
  DatagramSocket sendsocket = new DatagramSocket(SEND_PORT);
  //创建接受的Socket端
  DatagramSocket recesocket = new DatagramSocket(RECE_PORT);
  //发送线程建立
  send_thread = new Send_Thread(sendsocket, address);
  //接受线程的建立
  rece_thread = new Receive_Thread(recesocket);
  send_thread.start();
  rece_thread.start();

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

}

}

需要注意的时候运行的时候需要同时运行聊天服务器和客户端，才能够正常运行。
最终效果如下：

来源：https://blog.csdn.net/u011612364/article/details/110758853