You can change the Remote Desktop Connection port for your Windows server as an added security measure.
If your server uses a firewall, you need to open the new port on it. If you don't, you cannot access your server over RDC. The process to open the port depends on your firewall.
The instructions below are for ASDM version 6.4. However, if you have a PIX 501 Firewall or an ASA 5505 Firewall running an older version of ASDM, the menus might differ slightly, but the process is similar.
Depending on which Cisco ASDM version you have installed, several options might display. If so, click Run ASDM Applet.
Your browser must have Java enabled and allow pop-ups from your firewall management IP.