请用C语言写一个post请求，不允许使用curl库

好的，以下是一个使用C语言编写的基本的POST请求示例，不使用curl库：

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

#define BUFFER_SIZE 1024

void error(const char *msg) {
    perror(msg);
    exit(1);
}

int create_tcp_socket() {
    int sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock == -1) {
        error("Error creating socket");
    }
    return sock;
}

char *get_ip(const char *host) {
    struct hostent *hent;
    int iplen = 15; //XXX.XXX.XXX.XXX
    char *ip = (char *) malloc(iplen + 1);
    memset(ip, 0, iplen + 1);
    if ((hent = gethostbyname(host)) == NULL) {
        error("Error getting IP");
    }
    if (inet_ntop(AF_INET, (void *) hent->h_addr_list[0], ip, iplen) == NULL) {
        error("Error converting hostname to IP address");
    }
    return ip;
}

char *build_post_request(const char *host, const char *path, const char *content_type, const char *body) {
    char *request_format = "POST %s HTTP/1.1\r\n"
                           "Host: %s\r\n"
                           "Content-Type: %s\r\n"
                           "Content-Length: %ld\r\n"
                           "Connection: close\r\n"
                           "\r\n"
                           "%s";
    int request_length = snprintf(NULL, 0, request_format, path, host, content_type, strlen(body), body);
    char *request = (char *) malloc(request_length + 1);
    sprintf(request, request_format, path, host, content_type, strlen(body), body);
    return request;
}

void send_post_request(const char *host, const char *port, const char *path, const char *content_type, const char *body) {
    int sock = create_tcp_socket();
    char *ip = get_ip(host);

    struct sockaddr_in server_address;
    server_address.sin_family = AF_INET;
    server_address.sin_port = htons(atoi(port));
    if (inet_pton(AF_INET, ip, &(server_address.sin_addr)) <= 0) {
        error("Error converting IP address");
    }

    if (connect(sock, (struct sockaddr *) &server_address, sizeof(server_address)) == -1) {
        error("Error connecting to server");
    }

    char *request = build_post_request(host, path, content_type, body);

    if (send(sock, request, strlen(request), 0) == -1) {
        error("Error sending request");
    }

    char response[BUFFER_SIZE];
    memset(response, 0, sizeof(response));

    while (1) {
        int bytes_received = recv(sock, response, BUFFER_SIZE - 1, 0);
        if (bytes_received <= 0) {
            break;
        }
        printf("%s", response);
        memset(response, 0, sizeof(response));
    }

    free(request);
    free(ip);
    close(sock);
}

int main() {
    const char *host = "example.com";
    const char *port = "80";
    const char *path = "/your/api/endpoint";
    const char *content_type = "application/json";
    const char *body = "{\"key\":\"value\"}";

    send_post_request(host, port, path, content_type, body);

    return 0;
}

请将`example.com`替换为目标主机的域名或IP地址，`/your/api/endpoint`替换为实际的API端点，`{\"key\":\"value\"}`替换为您要发送的请求体内容。