[SOLVED] WinHttpSendRequest and ERROR_WINHTTP_RESEND

WinHttpSendRequest and ERROR_WINHTTP_RESEND_REQUEST

Is it possible for GetLastError() to return ERROR_WINHTTP_RESEND_REQUEST after calling WinHttpSendRequest?

Documentation for WinHttpSendRequest:

ERROR_WINHTTP_RESEND_REQUEST
The application must call WinHttpSendRequest again due to a redirect or authentication challenge. Windows Server 2003 with SP1, Windows XP with SP2 and Windows 2000: This error is not supported.

But samples from MSDN (Authentication in WinHTTP) checks for this value after WinHttpReceiveResponse.

Solution

But samples from MSDN (Authentication in WinHTTP) checks for this value after WinHttpReceiveResponse.

At a first glance the sample may look like that. But if you look closely, the sample actually checks for ERROR_WINHTTP_RESEND_REQUEST if either WinHttpSendRequest() or WinHttpReceiveResponse() fails:

// Send a request.
bResults = WinHttpSendRequest( hRequest,
                               WINHTTP_NO_ADDITIONAL_HEADERS,
                               0,
                               WINHTTP_NO_REQUEST_DATA,
                               0, 
                               0, 
                               0 );

// End the request.
if( bResults )
  bResults = WinHttpReceiveResponse( hRequest, NULL );

// Resend the request in case of 
// ERROR_WINHTTP_RESEND_REQUEST error.
if( !bResults && GetLastError( ) == ERROR_WINHTTP_RESEND_REQUEST)
    continue;

If WinHttpSendRequest() returns FALSE, the call to WinHttpReceiveResponse() will be skipped and GetLastError() will be checked for ERROR_WINHTTP_RESEND_REQUEST. This code is inside a while loop, so the continue statement will cause the remaining portion of the loop to be skipped so WinHttpSendRequest() will be called again.

Conclusion: The sample is in line with the reference documentation.