setsockopt和sendto搭配使用例子

setsockopt函数用于设置套接字选项，sendto函数用于向指定的目标地址发送数据。下面是一个setsockopt和sendto搭配使用的例子：

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>

int main() {
    int sockfd;
    struct sockaddr_in server_addr;
    char buffer[1024];

    // 创建套接字
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(8080);
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");

    // 设置套接字选项
    int optval = 1;
    socklen_t optlen = sizeof(optval);
    if (setsockopt(sockfd, SOL_SOCKET, SO_KEEPALIVE, &optval, optlen) < 0) {
        perror("setsockopt failed");
        exit(EXIT_FAILURE);
    }

    // 发送数据
    const char* message = "Hello, server!";
    if (sendto(sockfd, message, strlen(message), 0, (struct sockaddr*) &server_addr, sizeof(server_addr)) < 0) {
        perror("sendto failed");
        exit(EXIT_FAILURE);
    }

    printf("Message sent to server.\n");

    close(sockfd);

    return 0;
}