Here you can change the default port Microsoft Remote Desktop
Connections listening to.The default port is 3389.Changing this port
to another port provides a better security.It prevents that someone
from a public network or from your network can connect directly
to your PC by using the known default port.To change the port click your
way down to:

- HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control
\TerminalServer\WinStations\RDC-Tcp\

Locate here in the right pane the entry :

PortNumber

Doubleclick this entry , choose Decimal and enter the
new port number.

This requires no restart.Now when you want to establish
a Remote Desktop Connection enter the IP Address of the host
you want to connect and use a colon after it followed with the new
port number.Example: 192.168.2.13:3200

This will connect to 192.168.2.13 on port 3200.