I tried this in port forwarding, denying all access of the IP of the computer to the specific ports, though i'm guessing this has to be wrong due to the ability to still access steam. Below is what the setup page would look like, taken from someone on the internet's screen capture. I have deny always in the inbound filter setting and the correct ports and ip address in the other fields
NOTE THIS ISNT MY EXACT SET UP JUST WHAT IT LOOKS LIKE ON THE PAGE

link to screen shots of every page of the router
Screenshots - D-Link - DIR-655 (D-Link Firmware) | PcWinTech.com