I am trying to implement something very similar to a sample program Calvin Hsia created in MSDN to handle a "Callback" from a COM (http://msdn.microsoft.com/library/en-us/dnfoxgen7/html/vfpandcom.asp?frame=true#vfpandcom_topic10). The main difference is that I want to setup an indefinite number of "Callbacks" from different workstations and users, kind of an Observer pattern. Now, as I posted before, everything works fine if everything runs under the same user, I can run this from any computer and will run as I want. The problem lies that if it is another user that wants to "subscribe", then the call to GETINTERFACE fails.

Let me try to put it in a graph:

[Computer 1 User 1]  [Computer 2 User 1]  [Computer 3 User 2]
|                 |  |                 |  |                 |
|   COM Server    |  |    CLIENT 1     |  |    CLIENT 2     |
|_________________|  |_________________|  |_________________|

Now, for simplicity, let's say "COM Server" Only accepts one client simultaneously, so it would be like Calvin's sample program and it will have, somewhere:


Function Attach(toObserver)

this.Observer = getinterface(toObserver, 'Interface', 'myDLL.DLL')

Now the 'Interface' is, let's say, just one method, called 'Updated'
And somewhere when an event happens, we call the Observers updated method:

this.Observer.Updated()

And Client will have something like

loObserver = createobject('Some class that implements "Interface" from "myDLL.DLL")
loServer.AttachClient(loObserver)


Now, if the scenario is:

[Computer 1 User 1]  [Computer 2 User 1]
|                 |  |                 |
|   COM Server    |  |    CLIENT 1     |
|_________________|  |_________________|

Everything works fine and I am happy, I can even add more clients and all will work, from any computer as long as the user is "User 1", but with

[Computer 1 User 1]  [Computer 3 User 2]
|                 |  |                 |
|   COM Server    |  |    CLIENT 1     |
|_________________|  |_________________|

Then the call to GETINTERFACE() from "computer 3/User 2" fails with an Access Denied error, my guess is that it fails for toObserver is an object created by User 2, while the server itself is running under a different user, but I tried giving all kinds of permissions everywhere, in DCOM, in COM+, also all users are administrators of the machine that runs the Server, but nothing seems to work.

Any ideas?