HttpSendRequest fails

I was just working on a project, and I required a c++ code in which I could implement wininet functions to make an HTTPS request to a server. Here is the following code ...

void connect(LPCSTR hostname, LPCSTR endpoint) // hostname = "127.0.0.1", endpoint = "/"
{
    LPCWSTR userAgent = L"Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:138.0) Gecko/20100101 Firefox/138.0";
    HINTERNET hInternet = InternetOpenW(userAgent, INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0);
    if (hInternet == NULL) {
        perror("InternetOpenW");
        exit(EXIT_FAILURE);
    }

    HINTERNET hConnect = InternetConnect(hInternet, hostname, 443, NULL, NULL, INTERNET_SERVICE_HTTP, 0, 0);

    if (hConnect == NULL) {
        InternetCloseHandle(hInternet);
        perror("InternetConnect");
        exit(EXIT_FAILURE);
    }

    PCTSTR accept[] = {"application/json", NULL};

    HINTERNET hRequest = HttpOpenRequest(hConnect, "POST", endpoint, "HTTP/1.1", NULL, accept, INTERNET_FLAG_SECURE, 0);

    if (hRequest == NULL) {
        InternetCloseHandle(hInternet);
        InternetCloseHandle(hConnect);
        perror("HttpOpenRequest");
        exit(EXIT_FAILURE);
    }

    LPCSTR headers = "Content-Type: application/json\r\n";

    if (HttpAddRequestHeaders(hRequest, headers, -1L, HTTP_ADDREQ_FLAG_ADD) == false) {
        InternetCloseHandle(hInternet);
        InternetCloseHandle(hConnect);
        InternetCloseHandle(hRequest);
        perror("HttpAddRequestHeaders");
        exit(EXIT_FAILURE);
    }

    std::string data = "{\"sessionId\": \"importants.txt\", \"authToken\": \"Nothing Important Here.\"}";

    if (HttpSendRequest(hRequest, NULL, -1L, (LPVOID) data.c_str(), data.length()) == false) {
        InternetCloseHandle(hInternet);
        InternetCloseHandle(hConnect);
        InternetCloseHandle(hRequest);
        perror("HttpSendRequest");
        exit(EXIT_FAILURE);
    }

    std::string response = "";

    char buffer[4096];
    DWORD bytesRead;
    while (InternetReadFile(hRequest, buffer, sizeof(buffer) - 1, &bytesRead) && bytesRead > 0) {
        buffer[bytesRead] = '\0';
        response += buffer;
    }

    std::cout << response << std::endl;

    InternetCloseHandle(hInternet);
    InternetCloseHandle(hConnect);
    InternetCloseHandle(hRequest);
}

But when I try to compile it, it compiles well. Here's the command in case ...

x86_64-w64-mingw32-g++ harvester.cpp -o harvester.exe -l wininet -static-libstdc++ -static-libgcc

But when I try to run it using wine, it outputs something like this and exits ...

$ wine harvester.exe
MESA-INTEL: warning: Haswell Vulkan support is incomplete
MESA-INTEL: warning: Haswell Vulkan support is incomplete
HttpSendRequest: Success

My flask server at this point haven't even received a connection request, or else it would print a debug message. But if I try receiving the request using netcat, it shows something is received, but it's gibberish ...

$ nc -nvlp 443
listening on [any] 443 ...
connect to [127.0.0.1] from (UNKNOWN) [127.0.0.1] 54286
��A���3�fz�T�� J�M�_v��~�O�}�2�,̩���
�+���   �0̨��/����5���/�̪��9���3x

�@
"   127.0.0.1

#

^C

And then again the client exits with the previous message.

I can't understand where the bug is :(