Java可以使用UDP协议来进行网络通信的示例

当使用UDP协议进行网络通信时，需要使用`DatagramSocket`和`DatagramPacket`两个类来实现。下面是一个Java使用UDP协议进行网络通信的示例代码：

服务器端代码：

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class UDPServer {
    public static void main(String[] args) throws Exception {
        DatagramSocket serverSocket = new DatagramSocket(9876); // 创建UDP socket并绑定端口号

        byte[] receiveData = new byte[1024];
        byte[] sendData = new byte[1024];

        while (true) {
            DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
            serverSocket.receive(receivePacket); // 接收客户端请求

            String sentence = new String(receivePacket.getData());
            InetAddress IPAddress = receivePacket.getAddress();
            int port = receivePacket.getPort();

            String capitalizedSentence = sentence.toUpperCase();
            sendData = capitalizedSentence.getBytes();

            DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, port);
            serverSocket.send(sendPacket); // 发送响应给客户端
        }
    }
}

客户端代码：

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class UDPClient {
    public static void main(String[] args) throws Exception {
        DatagramSocket clientSocket = new DatagramSocket();

        InetAddress IPAddress = InetAddress.getByName("localhost");
        int port = 9876;

        byte[] sendData = new byte[1024];
        byte[] receiveData = new byte[1024];

        String sentence = "hello server";
        sendData = sentence.getBytes();

        DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, port);
        clientSocket.send(sendPacket); // 发送请求给服务器

        DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
        clientSocket.receive(receivePacket); // 接收服务器响应

        String modifiedSentence = new String(receivePacket.getData());
        System.out.println("FROM SERVER:" + modifiedSentence);

        clientSocket.close();
    }
}

这个示例代码中，客户端向服务器发送一个字符串请求，服务器收到请求后将字符串转为大写并返回给客户端。