java udp获取远程ip地址

以下是Java实现UDP获取远程IP地址的示例代码：

import java.net.*;

public class UdpRemoteAddress {

  public static void main(String[] args) throws Exception {

    // 创建UDP Socket
    DatagramSocket socket = new DatagramSocket();

    // 发送UDP消息
    String message = "Hello, world!";
    InetAddress address = InetAddress.getByName("127.0.0.1");
    int port = 9999;
    DatagramPacket packet = new DatagramPacket(message.getBytes(), message.length(), address, port);
    socket.send(packet);

    // 接收UDP消息
    byte[] buffer = new byte[1024];
    DatagramPacket receivePacket = new DatagramPacket(buffer, buffer.length);
    socket.receive(receivePacket);

    // 获取远程IP地址
    InetAddress remoteAddress = receivePacket.getAddress();
    int remotePort = receivePacket.getPort();
    System.out.println("Remote address: " + remoteAddress.getHostAddress() + ", port: " + remotePort);

    // 关闭UDP Socket
    socket.close();
  }
}

在上述代码中，首先创建了一个UDP Socket，并发送一条UDP消息到指定的IP地址和端口号，然后接收UDP消息，并通过`getAddress()`方法获取远程IP地址和端口号，最后输出远程IP地址和端口号，并关闭UDP Socket。