Communication between kernel-mode and user-mode application

Question

I have built a WFP callout driver which runs in kernel mode. Now, I'm trying to figure out how to communicate between this driver and my GUI application which runs in user-mode. Any ideas?

Exactly what I want is something like this:

1. The callout driver detects an incomming connection on port 4444 (This is not part of my question)
2. The drivers send a message to the user-mode app.
3. The app shows a notification to the user and asks it if we should accept/block the connection.
4. The user-mode app sends back the user's response to the callout driver.

Thanks!