To properly simulate a Form submission using WinInet, you need to send a header that indicates the proper Content-Type. For Forms, the proper Content-Type header is:
Content-Type: application/x-www-form-urlencoded
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 s
UCh '!' 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());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 removedHINTERNET 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-handlesFor more information about URL-encoding and the format of a Form POST request, see section 8.2 in RFC 1866.
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