如何在C中找到套接字连接状态？

#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>
#include <errno.h>

int main() {
    int sockfd;
    struct sockaddr_in server_addr;
    int optval;
    socklen_t optlen = sizeof(optval);

    // 创建套接字
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd == -1) {
        perror("socket");
        exit(EXIT_FAILURE);
    }

    // 设置服务器地址
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(8080);
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");

    // 连接套接字
    if (connect(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
        perror("connect");
        exit(EXIT_FAILURE);
    }

    // 获取套接字连接状态
    if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, &optlen) == -1) {
        perror("getsockopt");
        exit(EXIT_FAILURE);
    }

    if (optval == 0) {
        printf("套接字连接成功\n");
    } else {
        printf("套接字连接失败，错误码：%d\n", optval);
    }

    // 关闭套接字
    close(sockfd);

    return 0;
}