如何在进行多个连接时在C中设置套接字超时？

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

int set_socket_timeout(int sockfd, int timeout) {
    struct timeval tv;
    tv.tv_sec = timeout;
    tv.tv_usec = 0;
    return setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, (const char*)&tv, sizeof(tv));
}

int main() {
    int sockfd;
    struct sockaddr_in server_addr;
    
    // 创建套接字
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd == -1) {
        perror("socket");
        exit(1);
    }
    
    // 设置套接字为非阻塞模式
    int flags = fcntl(sockfd, F_GETFL, 0);
    fcntl(sockfd, F_SETFL, flags | O_NONBLOCK);
    
    // 设置超时时间为5秒
    if (set_socket_timeout(sockfd, 5) == -1) {
        perror("setsockopt");
        exit(1);
    }
    
    // 连接套接字
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(80);
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    
    int ret = connect(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr));
    if (ret == -1 && errno == EINPROGRESS) {
        // 连接操作正在进行中
        fd_set write_fds;
        FD_ZERO(&write_fds);
        FD_SET(sockfd, &write_fds);
        
        struct timeval tv;
        tv.tv_sec = 5;
        tv.tv_usec = 0;
        
        ret = select(sockfd + 1, NULL, &write_fds, NULL, &tv);
        if (ret == -1) {
            perror("select");
            exit(1);
        } else if (ret == 0) {
            // 连接超时
            printf("Connection timeout\n");
            exit(1);
        }
        
        // 恢复套接字阻塞模式
        fcntl(sockfd, F_SETFL, flags);
        
        // 检查连接状态
        int error;
        socklen_t len = sizeof(error);
        ret = getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &error, &len);
        if (ret == -1) {
            perror("getsockopt");
            exit(1);
        }
        
        if (error != 0) {
            printf("Connection error: %s\n", strerror(error));
            exit(1);
        } else {
            printf("Connection successful\n");
        }
    }
    
    close(sockfd);
    
    return 0;
}