Error Numbers with VB

[Seán Hennessy]

Folks, I'm a lowly VB developer with next to zero knowledge of how
error handling works in C++ apps. I'm writing a VB application using
WinHTTP 5.0, and I'm struggling to understand the error numbers I get
back. I need to trap specific errors and take action accordingly.

I took the error numbers I'm using from WinHTTP.h, which defines
ERROR_WINHTTP_TIMEOUT as 12002, or 0x2002 in Hex. The actual error
number I get back is -2147012894, which is 0x80072EE2 in Hex. Clearly
the rightmost 8 bytes are the number I want, but where does the rest
of the number come from?

I'd be very grateful for any information.

Thanks,
Seán

[Stephen Sulzer [Microsoft]]

Hello Seán,

Hey, there's nothing lowly about being a Visual Basic developer. :-)

The ERROR_WINHTTP_* error codes you see in WinHTTP.h are the Win32 error
codes that the WinHTTP Win32 API functions return. When using the
WinHttpRequest COM component, a (16-bit) Win32 error code is translated into
a (32-bit) HRESULT, which is the COM error code format. HRESULTs are
interpreted in hexadecimal, so if you get a value like -2147012894, the
first thing to do is to convert it to hex (0x80072EE2).

Win32 error codes translated into HRESULTs will be of the form 0x8007xxxx,
where 'xxxx' is the hexadecimal 16-bit Win32 error code. (The left-most '8'
in the HRESULT indicates a fatal error; the '7' indicates that the error
originated from a Win32 API.)

WinHTTP Win32 API error codes are in the 12001 to 12185 range; as COM
HRESULTs they will be in the range 0x80072EE1 to 0x80072F99.

Here is some official documentation on HRESULTs from the Platform SDK:

Structure of COM Error Codes
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/com/error_5g6r.asp

Error Handling
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/com/error_83qf.asp

Regards,

Stephen Sulzer
Microsoft Corporation

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