Here’s a handy guide to allowing you to connect to multiple Windows PC’s via Remote Desktop Connection, for each computer you want to remotely connect to you have to configure each computer to listen to different ports to avoid port conflicts by changing the registry key in…
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\TerminalServer\WinStations\RDP-Tcp\PortNumber
Select Port Numbers and make sure Decimal format is selected, then change the number. Now take that number you’ve chosen your computer to listen to and configure your router to port forward to that number. You may need to open up the new port on the PC if it has a firewall enabled.
To test your connection try to connect from outside your network just open up the Remote Desktop Client application then type in your home IP address (if you don’t know this, simply visit somewhere like whatismyip.com from within your home network), then add a double colon and the new port number you setup on your PC).