Step 1:
Simply open the steam browser, by pressing: View > Servers.
Step 2:
Click Add A Server button, this will open a dialog prompting you to input an IP/port.
Step 3:
Get your IP, e.g. 1.1.1.1:2555, and add +1 to your port; e.g. 1.1.1.1:2556, and then input this new IP/port into the box, then either press: Add This Address to Favourites or Find Games at this Address.
