linux c 判断能否上网

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

int is_internet_available() {
    int sockfd;
    struct sockaddr_in serv_addr;
    char *server_ip = "8.8.8.8";
    int server_port = 53; // DNS服务通常使用53端口

    if ((sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
        perror("socket creation failed");
        return 0;
    }

    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(server_port);

    if (inet_pton(AF_INET, server_ip, &serv_addr.sin_addr) <= 0) {
        perror("inet_pton failed");
        close(sockfd);
        return 0;
    }

    if (connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
        perror("connect failed");
        close(sockfd);
        return 0;
    }

    close(sockfd);
    return 1;
}

int main() {
    if (is_internet_available()) {
        printf("Internet is available.\n");
    } else {
        printf("No internet connection.\n");
    }
    return 0;
}