How to simulate a Form POST request by using WinInet

In many cases, the server does not respond appropriately if a Content-Type is not specified. For example, the Active Server Pages component of IIS 3.0 actually checks this header specifically for 'application/x-www-form- urlencoded' before adding form variables to the "Request.Form" object. This MIME/Content-Type indicates that the data of the request is a list of URL- encoded form variables. URL-encoding means that space character (ASCII 32) is encoded as '+', special character such '!' encoded in hexadecimal form as '%21'.

Here is a snippet of code that uses the MFC WinInet classes to simulate a Form POST request:

   CString strHeaders =

      _T("Content-Type: application/x-www-form-urlencoded");

   // URL-encoded form variables -

   // name = "John Doe", userid = "hithere", other = "P&Q"

   CString strFormData = _T("name=John+Doe&userid=hithere&other=P%26Q");



   CInternetSession session;

   CHttpConnection* pConnection =

      session.GetHttpConnection(_T("ServerNameHere"));

   CHttpFile* pFile =

      pConnection->OpenRequest(CHttpConnection::HTTP_VERB_POST,

                              _T("FormActionHere"));

   BOOL result = pFile->SendRequest(strHeaders,

      (LPVOID)(LPCTSTR)strFormData, strFormData.GetLength());

				

Without MFC, the same code translates to straight SDK calls as follows:

   static TCHAR hdrs[] =

      _T("Content-Type: application/x-www-form-urlencoded");

   static TCHAR frmdata[] =

      _T("name=John+Doe&userid=hithere&other=P%26Q");

  static LPSTR accept[2]={"*/*", NULL};



   // for clarity, error-checking has been removed

   HINTERNET hSession = InternetOpen("MyAgent",

      INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0);

   HINTERNET hConnect = InternetConnect(hSession, _T("ServerNameHere"),

      INTERNET_DEFAULT_HTTP_PORT, NULL, NULL, INTERNET_SERVICE_HTTP, 0, 1);

   HINTERNET hRequest = HttpOpenRequest(hConnect, "POST",

      _T("FormActionHere"), NULL, NULL, accept, 0, 1);

   HttpSendRequest(hRequest, hdrs, strlen(hdrs), frmdata, strlen(frmdata));

   // close any valid internet-handles