C++ FTP WinINet, can't download folder from FTP server

Question

I'm trying to download the folder named "public_html" but it's not doing anything in my program, here is my code.

int main(){
    cerr<<"Hello"<<endl;
    string spath = "C:/Users/"+GetUser()+"/Desktop";
    spath += str;
    LPCSTR path = spath.c_str();
    HINTERNET hInternet = InternetOpen(NULL, INTERNET_OPEN_TYPE_DIRECT, NULL, NULL, 0); // Initialization for WinInet Functions
    if (!hInternet) { cerr<<"error code is "<<GetLastError()<<"\n";
      system("pause");
      return 1; }

    // Starts a session in this case an FTP session
   HINTERNET hFtpSession = InternetConnect(hInternet,IP,INTERNET_DEFAULT_FTP_PORT,User,Pass, INTERNET_SERVICE_FTP,INTERNET_FLAG_PASSIVE,0);
    if(!hFtpSession) {
      InternetCloseHandle(hInternet);
      cerr<<"error code is "<<GetLastError()<<"\n";
      system("pause");
      return 2;
    }

   FtpGetFile(hFtpSession, str, path, false, NULL, FTP_TRANSFER_TYPE_BINARY, NULL);
   // Uploads the file C:\\Test.txt onto the FTP server as Test.txt

   InternetCloseHandle(hFtpSession); // Close hFtpSession
   InternetCloseHandle(hInternet); // Close hInternet
    return 0;
}

This works when i download single files at a time but not when i do it with folders. Why not? btw

LPCSTR str = "/public_html";

Answer 1

This is the problem when dealing with libraries or APIs that tend to abstract the underlying principles: you end up not understanding what is truly happening on your machine, and aren't able to easily determine what functions to use for what purpose.

To answer this question, you have to take a step back and look at FTP itself.

The function you use is called FtpGetFile and not FtpGetFolder. FTP itself stands for file transfer protocol.

No matter how awesome of a library you're using, you cannot tell a FTP server that your client wants it to give it an entire folder to download. You can only download one file at a time. So the solution is to request a list of files in that folder, then write a function to traverse over the response and download each individual file, recursing as needed to handle nested folders/directories.