[python-win32] How to write a COM Server implementing interfaces from type lib?

[Mark Hammond]

On 22/03/2012 2:53 AM, Jan Wedel wrote:
> Hi,
>
> I'm currently having trouble to write a COM-Server that has some special
> requirements:
> - It needs to derive from IUnknown
> - It needs to implement multiple interface from two different
> proprietary typelibs (dlls)
> - It needs to implement a custom category
>
> At first I started with pythoncom. I used the attribute _reg_catids_ to
> specify the category and _com_interfaces_ to specify the interfaces I
> want to implement. The client (proprietary 3rd party sw, no source) sees
> the server but throws some 0x80004005 error on CoCreateInstance.

That's E_FAIL which is pretty generic.  Doesn't sound like a simple 
failure to QI for the correct interface.

win32com should be able to do this given there is a tlb - see the 
"pippo" samples.  Further, using the debug facilities and 
win32traceutil, you should be able to see the creation of the object, 
the QIs on the object and any methods actually called.  But as 
mentioned, I doubt it is a QI failure.

> I was hoping that I can just tell the COM dispatcher, "yes, I have these
> interface implemented" and implement the methods without really having
> the interface classes available.
>
> I read, that pythoncom can only create components that use IDispatch so
> I guess the _com_interfaces_ idea won't work, will it?

As above, you should be able to fully implement them so long as makepy 
has been run.

> Then I did some further research and found comtypes. I tried to write a
> server stub again. I used GetModule to load the type library containing
> the Interfaces, importing the generated interface classes and let the
> main server class extend these interfaces.
>
> The first problem was, that comtypes did not support the _reg_catids_
> attribute or anything similar so I had to add the Implemented Categories
> key manually to the registry.
> Then, I was able to see the server through the client, which obviously
> filters by categories, but it still shows the same error as before.
>
> So, what is the correct/best way to implement a server that needs to
> implement custom interfaces and categories? Or is it possible at all
> using python?

The fact you get the same error there implies something else is going 
wrong, but it is impossible to guess what.  Have you tried contacting 
the author of the object?

Mark

>
> Thanks!
>
> //Jan
>
>
>
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