How exactly is data transmitted in the HTTP protocol?

In the HTTP protocol, data transfer is carried out through requests and responses, which consist of:

1. Request/Status Line — indicates the method (GET, POST, etc.) and URL or response status.
2. Headers — metadata such as content type, length, cookies.
3. Message Body — contains the transmitted data (e.g., JSON, HTML, file).

Data can be transmitted in the request body (for example, in POST) or in the URL (for example, parameters in GET). In C/C++, libraries (libcurl) are usually used to work with HTTP, which form and send these components over the network.

Example with libcurl (sending a POST request):

#include <curl/curl.h>

CURL *curl = curl_easy_init();
if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "http://example.com/api");
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, "param1=value1&param2=value2");
    CURLcode res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
}

Thus, data is transmitted in the body of the HTTP request.