“A specified communication resources(port) is already in use” when attaching the debugger

Question

I have just upgrade my windows phone 8 to windows phone 8.1. When I connect my phone to pc and run my project it gives me

Answer 1

Project GUID conflict

Yet another possible reason for this error is the Project GUID conflict. If the project / app GUID of the application you are trying to debug is the same as the GUID of another application installed from the store (can be the same application, and doesn't matter if you already uninstalled it), this error may occur.

I was testing in-app purchases for my app for which purpose I had to change the app GUID in WMAppManifest.xml and AssemblyInfo.cs to the GUID from the Windows Phone Store. Having the app installed from the store itself (for testing purposes) previously, I uninstalled it for the purpose of debugging. Yet that didn't help and anytime I changed my app GUID to match Windows Store App Guid I got this error. Changing the GUID back to the original project's GUID caused the error to go away and debugging was working well again.

VS2013 Ultimate Update 2, testing with 8.1 Device.