帮我实现一个TCP客户端，用C语言实现，要求有超时处理机制，心跳检测机制

好的，我可以回答这个问题。以下是一个简单的TCP客户端的C语言实现，包括超时处理机制和心跳检测机制：

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

#define SERVER_IP "127.0.0.1"
#define SERVER_PORT 8888
#define TIMEOUT_SEC 5
#define HEARTBEAT_INTERVAL 10

int main() {
    int sockfd;
    struct sockaddr_in server_addr;
    char buf[1024];
    int ret, len;
    fd_set readfds;
    struct timeval timeout;
    time_t last_heartbeat_time;

    // 创建socket
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        perror("socket");
        exit(1);
    }

    // 设置非阻塞模式
    int flags = fcntl(sockfd, F_GETFL, 0);
    fcntl(sockfd, F_SETFL, flags | O_NONBLOCK);

    // 设置服务器地址
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = inet_addr(SERVER_IP);
    server_addr.sin_port = htons(SERVER_PORT);

    // 连接服务器
    ret = connect(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr));
    if (ret < 0 && errno != EINPROGRESS) {
        perror("connect");
        exit(1);
    }

    // 等待连接完成或超时
    FD_ZERO(&readfds);
    FD_SET(sockfd, &readfds);
    timeout.tv_sec = TIMEOUT_SEC;
    timeout.tv_usec = 0;
    ret = select(sockfd + 1, NULL, &readfds, NULL, &timeout);
    if (ret < 0) {
        perror("select");
        exit(1);
    } else if (ret == 0) {
        printf("connect timeout\n");
        exit(1);
    } else {
        int error = 0;
        socklen_t len = sizeof(error);
        getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &error, &len);
        if (error != 0) {
            printf("connect failed: %s\n", strerror(error));
            exit(1);
        }
    }

    // 连接成功，设置为阻塞模式
    fcntl(sockfd, F_SETFL, flags);

    // 发送心跳包
    last_heartbeat_time = time(NULL);
    while (1) {
        // 检查是否需要发送心跳包
        time_t now = time(NULL);
        if (now - last_heartbeat_time >= HEARTBEAT_INTERVAL) {
            ret = send(sockfd, "heartbeat", strlen("heartbeat"), 0);
            if (ret < 0) {
                perror("send");
                exit(1);
            }
            last_heartbeat_time = now;
        }

        // 等待读事件或超时
        FD_ZERO(&readfds);
        FD_SET(sockfd, &readfds);
        timeout.tv_sec = TIMEOUT_SEC;
        timeout.tv_usec = 0;
        ret = select(sockfd + 1, &readfds, NULL, NULL, &timeout);
        if (ret < 0) {
            perror("select");
            exit(1);
        } else if (ret == 0) {
            printf("timeout\n");
            continue;
        }

        // 读取数据
        len = recv(sockfd, buf, sizeof(buf), 0);
        if (len < 0) {
            if (errno == EAGAIN || errno == EWOULDBLOCK) {
                printf("no data\n");
                continue;
            } else {
                perror("recv");
                exit(1);
            }
        } else if (len == 0) {
            printf("server closed\n");
            exit(1);
        } else {
            buf[len] = '\0';
            printf("recv: %s\n", buf);
        }
    }

    // 关闭socket
    close(sockfd);

    return 0;
}