When attempting to add a Microsoft Windows or Microsoft Hyper-V Server to the VembuBDR server, an error occurs during the installation of the Vembu Integration Service. The error message indicates that the Vembu Integration Service Port (42005) is already in use.

This error may arise due to the following reasons:

1. Port 42005, which is required by the Vembu Integration Service, is already in use by another process.

2. The remote registry service is not running on the Windows Server or Hyper-V host.

3. The Windows Management Instrumentation (WMI) service is disabled on the BDR server side.

Solution 1: Port Conflict

If the Vembu Integration Service port 42005 is being utilized by another process, follow these steps:

1. Open a command prompt on the Microsoft Windows Server or Hyper-V host machine.

2. Type the following command to check for processes using port 42005:

netstat -ano | find "42005"

The result will be similar to this output: "TCP 0.0.0.0:42005 0.0.0.0:0 LISTENING 1772." Note the PID from the output (in this case, 1772).

3. In the Windows Task Manager, identify the application associated with the noted PID (1772 in this example). 

4. If possible, change the port used by that application to something other than "42005." Once done, attempt to add the Microsoft Windows Server or Hyper-V server to VembuBDR again.

Solution 2: Remote Registry Service

If the remote registry service is not running on the Windows Server or Hyper-V host, refer to KB-106002 for guidance on enabling it.

Solution 3: Enabling WMI Service

When the Windows Management Instrumentation (WMI) service is disabled on the BDR server side, follow these steps to enable it:

1. Open the Windows Services Console:

1. Press `Win + R` to open the Run dialog.
2. Type "Services.msc" and press Enter.
   

2. In the Services console, locate "Windows Management Instrumentation" in the list.

3. If the service is disabled, enable it by right-clicking it and selecting "Properties."

4. In the Properties window, change the startup type from "Disabled" to "Automatic."

5. Start the service by clicking the "Start" button.

After enabling and starting the WMI service, attempt to add the Microsoft Windows Server or Hyper-V server to VembuBDR again.