linux下网络端口连通性检测c语言

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

int check_tcp_port(const char *ip, int port) {
    int sockfd;
    struct sockaddr_in serv_addr;

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

    // 设置服务器地址结构体
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(port);
    if (inet_pton(AF_INET, ip, &serv_addr.sin_addr) <= 0) {
        perror("inet_pton");
        close(sockfd);
        return -1;
    }

    // 尝试连接
    if (connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) == -1) {
        perror("connect");
        close(sockfd);
        return 0; // 连接失败，端口未开放
    }

    close(sockfd);
    return 1; // 连接成功，端口开放
}

int main(int argc, char *argv[]) {
    if (argc != 3) {
        fprintf(stderr, "Usage: %s<IP> <port>\n", argv[0]);
        return 1;
    }

    const char *ip = argv[1];
    int port = atoi(argv[2]);

    if (check_tcp_port(ip, port)) {
        printf("Port %d is open\n", port);
    } else {
        printf("Port %d is closed or filtered\n", port);
    }

    return 0;
}

#include <sys/select.h>

int connect_with_timeout(int sockfd, struct sockaddr *addr, socklen_t addrlen, int timeout) {
    fd_set writefds;
    struct timeval tv;

    // 设置非阻塞模式
    fcntl(sockfd, F_SETFL, O_NONBLOCK);

    if (connect(sockfd, addr, addrlen) < 0 && errno != EINPROGRESS) {
        return -1;
    }

    // 初始化读写集合
    FD_ZERO(&writefds);
    FD_SET(sockfd, &writefds);

    // 设置超时时间
    tv.tv_sec = timeout;
    tv.tv_usec = 0;

    // 等待连接完成或超时
    if (select(sockfd + 1, NULL, &writefds, NULL, &tv) > 0) {
        int so_error;
        socklen_t len = sizeof(so_error);
        getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &so_error, &len);
        if (so_error == 0) {
            return 0; // 连接成功
        } else {
            return -1; // 连接失败
        }
    } else {
        return -1; // 超时
    }
}