I need .NET or C++ source code that simulates a device-side USB device driver?

I need to modify this device-side simulator to upload our protocol format to a Windows GUI.

Background:
I need to simulate our embedded ARM device because it's not available while. On Windows, I have a .NET GUI that needs to download a high-speed stream from the embedded ARM.

SO FAR...
I successfully added LibUsbDotNet (libUSB-Win32) to my .NET GUI.

Now I want to bring up the USB host-side communication at the GUI, and need to simulate the embedded device-side USB driver, which will simulate and upload a data stream to the USB host (ie. the .NET GUI on Windows).

I am open to running this device-side USB sim on either same computer as the host-side GUI, or on a 2nd Windows computer, connected to the first by a USB bridge cable.

I believe this will also benefit the general embedded system programming community.