How to run two different applications using the same VR device?

Hi,
I’m developing a VR application using QT and using UE4 to do full body IK. The problem is that when I launch the UE4 app, my QT application crashes. I don’t know if this is a UE4 issue or a steamVR issue. Can someone shed light on the matter?

The UE4 app is run in non-VR mode, i.e., it is not intended to supply display. I do the IK by querying position of the hmd/trackers using “Enumerate tracked devices” instead of using motion controller objects. From my UE4 app, i send the bone transform data using VRPN to the QT app.

Thanks,