Linux 获取 套接字 状态

int getsockopt(int sockfd, int level, int optname, void *optval, socklen_t *optlen);

#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>

int main() {
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        perror("socket");
        return 1;
    }

    int optval;
    socklen_t optlen = sizeof(optval);

    if (getsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &optval, &optlen) < 0) {
        perror("getsockopt");
        close(sockfd);
        return 1;
    }

    printf("SO_REUSEADDR is %s\n", optval ? "enabled" : "disabled");

    close(sockfd);
    return 0;
}

int fcntl(int fd, int cmd, ... /* arg */ );

#include <stdio.h>
#include <fcntl.h>

int main() {
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        perror("socket");
        return 1;
    }

    int flags = fcntl(sockfd, F_GETFL, 0);
    if (flags < 0) {
        perror("fcntl");
        close(sockfd);
        return 1;
    }

    printf("Socket flags: %d\n", flags);

    close(sockfd);
    return 0;
}