RDP transports on TCP 3389 by default for all supported versions of Windows; if you want to change the port, it requires a quick change in the Windows registry.

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp]

In this hive, the PortNumber value contains the configured port that Windows will listen for RDP connections. The default port assignment is represented as D3D in hexadecimal or 3389 in binary. 

It may require a reboot to make the port assignment take effect.

The Windows Server system will now listen on the new port with the Svchost.exe process, visible in task manager by entering Netstat  -a -n -o to view the current processes and list the associated executable.