Java实现基于UDP协议的网络通信UDP编程

package com.study.srv.demo18;
import java.io.IOException;
import java.net.*;
/**
 * @version 1.0
 * UDP发送端
 */
public class Demo11 {
    public static void main(String[] args) throws IOException {
        //1.创建DatagramSocket对象，准备发送和接收数据,在9998端口接收
        DatagramSocket datagramSocket = new DatagramSocket(9998);
        //2.将需要发送的数据，封装到DatagramPacket对象
        String s="发送的数据";
        byte[] buf=s.getBytes();
        InetAddress ip = InetAddress.getByName("192.168.0.18");
        //说明：封装的DatagramPacket对象
        //buf 内容字节数组
        //buf.length 数据长度
        //ip 主机（ip）
        //9999 端口
        DatagramPacket packet = new DatagramPacket(buf, buf.length, ip, 9999);
        //发送数据
        datagramSocket.send(packet);
        //关闭资源
//        datagramSocket.close();
        System.out.println("发送完毕");
        //发送端变为接收端接收数据
        byte[] bytes = new byte[1024];
        DatagramPacket datagramPacket = new DatagramPacket(bytes, bytes.length);
        datagramSocket.receive(datagramPacket);
        int length = datagramPacket.getLength();
        byte[] data = datagramPacket.getData();
        String string = new String(data, 0, length);
        System.out.println(string);
        datagramSocket.close();
        System.out.println("接受结束");
    }
}

package com.study.srv.demo18;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
/**
 * @version 1.0
 *UDP接收端
 */
public class Demo10 {
    public static void main(String[] args) throws IOException {
        //1．创建一个 DatagramSocket对象，准备在9999接收数据
        DatagramSocket datagramSocket = new DatagramSocket(9999);
        //2．构建一个DatagramPacket 对象，准备接收数据
        //在UDP协议，一个数据包最大64k
        byte[] buf=new byte[1024];
        DatagramPacket packet = new DatagramPacket(buf, buf.length);
        //3.接收方法 将通过网络传输的DatagramPacket对象填充到packet里去。
        System.out.println("接收端等待接收");
        datagramSocket.receive(packet);
        //4.可以对packet进行拆包，取出数据，并显示
        //实际接收到的数据字节长度
        int length = packet.getLength();
        //实际接收到的数据
        byte[] data = packet.getData();
        String string = new String(data, 0, length);
        System.out.println(string);
        //5.关闭资源
//        datagramSocket.close();
        System.out.println("接收结束");
        //接收端变为发送端，发送数据
        String s="接收端变为发送端，发送数据";
        byte[] bytes=s.getBytes();
        DatagramPacket datagramPacket = new DatagramPacket(bytes, bytes.length, InetAddress.getByName("192.168.0.18"), 9998);
        datagramSocket.send(datagramPacket);
        datagramSocket.close();
        System.out.println("发送完毕");
    }
}