Discord HTTPS POST with C

Question

I'm trying to build a Discord API with C (libdiscord it's constantly crashing).

I have found this promosing code (found here):

#include <stdio.h> /* printf, sprintf */
#include <stdlib.h> /* exit */
#include <unistd.h> /* read, write, close */
#include <string.h> /* memcpy, memset */
#include <sys/socket.h> /* socket, connect */
#include <netinet/in.h> /* struct sockaddr_in, struct sockaddr */
#include <netdb.h> /* struct hostent, gethostbyname */

void error(const char *msg) { perror(msg); exit(0); }

int main(int argc,char *argv[])
{
    /* first what are we going to send and where are we going to send it? */
    int portno =        80;
    char *host =        "api.somesite.com";
    char *message_fmt = "POST /apikey=%s&command=%s HTTP/1.0\r\n\r\n";

    struct hostent *server;
    struct sockaddr_in serv_addr;
    int sockfd, bytes, sent, received, total;
    char message[1024],response[4096];

    if (argc < 3) { puts("Parameters: <apikey> <command>"); exit(0); }

    /* fill in the parameters */
    sprintf(message,message_fmt,argv[1],argv[2]);
    printf("Request:\n%s\n",message);

    /* create the socket */
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) error("ERROR opening socket");

    /* lookup the ip address */
    server = gethostbyname(host);
    if (server == NULL) error("ERROR, no such host");

    /* fill in the structure */
    memset(&serv_addr,0,sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(portno);
    memcpy(&serv_addr.sin_addr.s_addr,server->h_addr,server->h_length);

    /* connect the socket */
    if (connect(sockfd,(struct sockaddr *)&serv_addr,sizeof(serv_addr)) < 0)
        error("ERROR connecting");

    /* send the request */
    total = strlen(message);
    sent = 0;
    do {
        bytes = write(sockfd,message+sent,total-sent);
        if (bytes < 0)
            error("ERROR writing message to socket");
        if (bytes == 0)
            break;
        sent+=bytes;
    } while (sent < total);

    /* receive the response */
    memset(response,0,sizeof(response));
    total = sizeof(response)-1;
    received = 0;
    do {
        bytes = read(sockfd,response+received,total-received);
        if (bytes < 0)
            error("ERROR reading response from socket");
        if (bytes == 0)
            break;
        received+=bytes;
    } while (received < total);

    if (received == total)
        error("ERROR storing complete response from socket");

    /* close the socket */
    close(sockfd);

    /* process response */
    printf("Response:\n%s\n",response);

    return 0;
}

But I need to send a header and data, according to this post (in Python):

import requests
import json

channelID = "your_id_goes_here" # enable dev mode on discord, right-click on the channel, copy ID
botToken = "your_token_here"    # get from the bot page. must be a bot, not a discord app

baseURL = "https://discordapp.com/api/channels/{}/messages".format(channelID)
headers = { "Authorization":"Bot {}".format(botToken),
            "User-Agent":"myBotThing (http://some.url, v0.1)",
            "Content-Type":"application/json", }

message = "hello world"

POSTedJSON =  json.dumps ( {"content":message} )

r = requests.post(baseURL, headers = headers, data = POSTedJSON)

I'm sorry, I don't know the protocols in detail.

I'd like to read messages too, but for now I'm OK just writing they.

UPDATE:

My new code (error 400, bad request).

#include <stdio.h>
#include <curl/curl.h>

int main(void)
{
    CURL *curl = NULL;
    CURLcode res;
    const char *data = "{\"content\": \"data to send\"}";
    const char *ID = "...";
    const char *token = "...";

    char tmp[1024];

    curl = curl_easy_init();

    if(curl != NULL) {
        struct curl_slist *headers = NULL;

        /* Remove a header curl would otherwise add by itself */
        headers = curl_slist_append(headers, "Accept:");

        /* Add a custom header */
        sprintf(tmp, "Host: https://discordapp.com/api/channels/%s/messages", ID);
        headers = curl_slist_append(headers, tmp);
        sprintf(tmp, "Authorization: Bot %s", token);
        headers = curl_slist_append(headers, tmp);
        headers = curl_slist_append(headers, "User-Agent: myBotThing (http://some.url, v0.1)");
        headers = curl_slist_append(headers, "Content-Type: application/json");

        /* set our custom set of headers */
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

        sprintf(tmp, "https://discordapp.com/api/channels/%s/messages", ID);
        curl_easy_setopt(curl, CURLOPT_URL, tmp);
        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);

        // POST
        curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "POST");
        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data);

        res = curl_easy_perform(curl);

        /* Check for errors */
        if(res != CURLE_OK) printf("curl_easy_perform() failed: %s\n", curl_easy_strerror(res));


        curl_easy_cleanup(curl);
        curl_slist_free_all(headers);
    }

    return 0;
}