Changing the Default RDP Port (3389) on Windows

3389 port number Simply put, the default port for using the Remote Desktop Protocol is 3389. This port should be open through Windows Firewall to make it RDP accessible within the local area network. If you want to make it accessible over the Internet (which is not safe), the RDP port should be forwarded through the main Internet router to work properly..

port 3389  Learn how port 3389 enables secure Remote Desktop Protocol (RDP) access. Discover its functions, security risks, and 8 best practices for maximizing protection.

3389 port used for  Remote Desktop allows remote connections to computers running Windows or Windows Server over the Remote Desktop Protocol (RDP), listening on port 3389 by default. For security or configuration purposes, you might want to change this listening port. This article provides step-by-step instructions to modify the listening port using either PowerShell or the Registry Editor.