By default, remote desktop connection uses port 3389. To check, open the "remote desktop connection" window and click on the show options button. In the general tab, find the "computer:" field and append ":3389" after the computer name and press enter. Alternatively, open the registry editor and navigate to "hkey_local_machinesystemcurrentcontrolsetcontrol erminal serverwinstations\rdp-tcp" to check the port.