基于c++ 实现一个udp server程序，监听广播IP地址为255.255.255.255 端口为13400的client发送的请求消息，解析client的ip地址，并给clientf发送应答

以下是一个基于C++实现的UDP服务器程序，可以监听广播IP地址为255.255.255.255，端口为13400的客户端发送的请求消息，解析客户端的IP地址，并给客户端发送应答。

#include <iostream>
#include <cstring>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>

using namespace std;

int main()
{
    // 创建UDP套接字
    int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if(sockfd == -1)
    {
        cerr << "socket() failed!" << endl;
        return -1;
    }

    // 允许广播
    int broadcast = 1;
    if(setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof(broadcast)) == -1)
    {
        cerr << "setsockopt() failed!" << endl;
        close(sockfd);
        return -1;
    }

    // 绑定本地IP和端口
    struct sockaddr_in addr;
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = htonl(INADDR_ANY);
    addr.sin_port = htons(13400);
    if(bind(sockfd, (struct sockaddr*)&addr, sizeof(addr)) == -1)
    {
        cerr << "bind() failed!" << endl;
        close(sockfd);
        return -1;
    }

    // 接收客户端请求
    char recv_buf[1024];
    struct sockaddr_in client_addr;
    socklen_t len = sizeof(client_addr);
    while(true)
    {
        memset(recv_buf, 0, sizeof(recv_buf));
        int n = recvfrom(sockfd, recv_buf, sizeof(recv_buf), 0, (struct sockaddr*)&client_addr, &len);
        if(n == -1)
        {
            cerr << "recvfrom() failed!" << endl;
            continue;
        }

        // 解析客户端IP地址
        char client_ip[INET_ADDRSTRLEN];
        memset(client_ip, 0, sizeof(client_ip));
        if(inet_ntop(AF_INET, &client_addr.sin_addr, client_ip, sizeof(client_ip)) == NULL)
        {
            cerr << "inet_ntop() failed!" << endl;
            continue;
        }
        cout << "Received request from " << client_ip << endl;

        // 发送应答
        const char* send_buf = "Hello, client!";
        n = sendto(sockfd, send_buf, strlen(send_buf), 0, (struct sockaddr*)&client_addr, len);
        if(n == -1)
        {
            cerr << "sendto() failed!" << endl;
            continue;
        }
    }

    // 关闭套接字
    close(sockfd);

    return 0;
}

这个程序使用了socket、setsockopt、bind、recvfrom、inet_ntop和sendto等函数实现了UDP服务器的基本功能。在运行时，该程序会不断接收客户端发送的请求消息，并解析客户端的IP地址，最后给客户端发送应答消息。