Guide to check the RDP port used on Windows server.
Login to your windows server
Buka Powershell dari search > Powershell elevated as admin
Then paste the following command
Get-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp' -name "PortNumber"Then the RDP port currently used on your Windows server will appear.