AndroidStudio doing AndroidInstrument 'unit' tests: Address already in use: connect

This is NOT a duplicate. Every other case of this error deals with ports and TCP and or sockets. There is no such thing in this case or in my code.

All I am doing is trying to run a unit test that has to run on the Android. I do it a couple of times and then I can get this error Address already in use: connect

and the apk cant get installed.

WTF? The code involves no TCP or sockets or ports. There is just a USB cable between Android Studio running on my PC and the Android device. How and why does this error happen? Rebooting the device and restarting Android Studio does not solve the problem. Rebooting my PC might.

Does any one have an idea of how to solve this short of a PC reboot?