C语言实现网络断开与重连的代码

下面是一个简单的 C 语言代码示例，用于检测网络连接状态并在发现断开连接时重新连接：

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

#define SERVER_ADDR "127.0.0.1"
#define SERVER_PORT 8080
#define MAX_BUF_SIZE 1024

int sockfd;

void sig_handler(int signo) {
    if (signo == SIGINT) {
        printf("Received SIGINT signal, closing socket and exiting...\n");
        close(sockfd);
        exit(0);
    }
}

int connect_to_server() {
    struct sockaddr_in servaddr;
    int sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock == -1) {
        perror("socket error");
        return -1;
    }

    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(SERVER_PORT);

    if (inet_pton(AF_INET, SERVER_ADDR, &servaddr.sin_addr) <= 0) {
        perror("inet_pton error");
        return -1;
    }

    if (connect(sock, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1) {
        perror("connect error");
        return -1;
    }

    return sock;
}

int main(int argc, char *argv[]) {
    signal(SIGINT, sig_handler);

    char buf[MAX_BUF_SIZE];
    int n;
    sockfd = connect_to_server();

    while (1) {
        if (sockfd == -1) {
            printf("Connection lost, retrying in 5 seconds...\n");
            sleep(5);
            sockfd = connect_to_server();
            continue;
        }

        n = read(sockfd, buf, MAX_BUF_SIZE);
        if (n == -1) {
            perror("read error");
            close(sockfd);
            sockfd = -1;
            continue;
        }

        if (n == 0) {
            printf("Connection closed by server, retrying in 5 seconds...\n");
            close(sockfd);
            sockfd = -1;
            sleep(5);
            continue;
        }

        printf("Received %d bytes from server: %s\n", n, buf);
    }

    return 0;
}

这个代码示例中，我们使用了 `socket`、`connect`、`read` 函数连接到服务器并不断读取数据。如果连接断开，我们会在 5 秒后尝试重新连接。如果服务器关闭了连接，我们也会在 5 秒后尝试重新连接。当我们收到 SIGINT 信号时，我们会关闭套接字并退出程序。

你需要根据你的实际需求进行修改，并根据你的操作系统和编译器来编译和运行代码。