Communication between Windows Store app and native desktop application

If you are talking about an application going into the Store, communication with the local system via any mechanism is not allowed. Communication with the local system is supported in some debug scenarios to make app development easier.

You can launch desktop applications from Windows Store applications with file or protocol handlers, but there is no direct communication.

So, to reiterate the point... communication between WinRT and the desktop is not allowed for released Windows Store applications. Communication between the two environments is allowed in debug only.

The PG has posted in different places reasons for why communication is not allowed, ranging from security, to the WinRT lifecycle (i.e., you app gets suspended - how does that get handled re: resources, sockets, remote app, etc. -- lots of failure points) and the fact that Store apps cannot have a dependency on external programs (i.e., I need your local desktop app/service for the app to run, but how do I get your app/service installed? You cannot integrate into the Store app. You can provide another Store desktop app entry, but that is a bad user experience.) Those are high level summaries, of course.