To change the default port 3389 in the Remote Desktop (RDP) service, you will need to change the registry settings on the computer running the RDP server. Please note that changing the RDP port may affect the ability of remote clients to connect, so be careful when changing it.

Here’s how to change the default RDP port:

1. open the Registry Editor on the RDP server. You can do this by pressing Win + R, typing “regedit” and pressing Enter.

2. Navigate to the next path in the registry editor:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp

3 Find the key named “PortNumber” and double-click it to open its properties.

4. In the Change DWORD Value window, select Decimal and enter the new port number. Make sure that the new port is not being used by other services or applications.

5. Click OK to save your changes.

6. Restart the Remote Desktop service or restart your computer for the changes to take effect.

After that, the remote desktop service will listen to the new port you specified. When connecting remote clients, you will need to specify a new port in the appropriate field when using the remote desktop program.