Hi,
Don't know if this is accurate or not, but there are other ways of blocking him out of that Steam site or any other web site. You can go to his computer and login as an Administrator or Owner account if he doesn't have that. Go to
IE and right-click on the
Gear Icon, then go to the
SECURITY TAB, click on the
RESTRICTED SITES icon, and then the
SITES button. In the
"ADD SITES TO THIS ZONE" box, type in or Paste the Steam site url, such as
http://store.steampowered.com/and simply click the
ADD BUTTON to add the Steam site to the list of restricted websites list below.
This will effectively block him from the Steam site or any other gaming sites you wish to block him from. The issue here, is that kids today are smart, so if he has another browser program such as Chrome, Firefox, or Safari also installed on that computer, he will simply use another browser program to access his gaming sites. If he has none of these other browsers, you effectively have blocked him from any websites you don't want him to go to. Not quite as effective as the Router port blocking. If he does have some or all those other browsers, you'd have to duplicate the restricted sites list in each of those other browsers. That can be done but it takes some work, since each of those other browsers have the restricted sites settings in a different place.
Some other things you can try:
1) Install Parental Control software from Norton or McAfee if you are running those; the downloads are free, and they will block out an individual Windows User or all Windows Users on the computer he is using.
2) Download and Install either NetNanny or CyberPatrol parental control programs and enter the list of sites such as Steam into the restricted sites list, similar to doing it in IE as above. These programs, as the programs in #1 not only block him from sites you designate, but also provide a comprehensive log of every single site he visits using his account down to the second. Usage is recorded
24x7x365 UNTIL YOU TURN IT OFF. This is very usefuly to see if he's visiting other dangerous sites that you don't know about.
3) If you have another computer in your home, create a Limited User account with his name on it, such as "Jack". This will prevent him from installing ANY new programs or plug-ins or add-ons to Browsers (such as BHOs) which are used in just about all online gaming platforms. He can surf the web normally via Google or Yahoo!, but he will not be able to install any Games or anything like Chat programs.
4) If you insist on giving him ownership priveleges on his own computer or on yours, then you need to simply stand there over his shoulder the entire time he's using his computer or your computer to surf the web for homework. Some parents I know employ this method, and make their kids sit in the family room if they have a shared household computer, and watch them the entire time.
I never did this myself; being an IT guy, I did sneaky router port blocking as you are attempting to do, and installed various parental control software onto my son's computer with a limited Windows account. He couldn't install any programs without asking me, and I knew 100% everywhere he visited on the Internet!!
Other parents I know employ a more brute-force method. If their kid has a laptop and they've misused it; they simply take the laptop away from the kid and lock it up where they can't get it. If the kid has homework to do for school, they force the kid to use a shared home PC in a common area; not in their rooms behind a closed door where they cannot be constantly monitored; or employ Windows account security as I've already mentioned. Some parents when they do this, will tell the kid to go their local library as most have free Internet computer access for 1 hr per day. Another effective solution, as the libraries all have built-in parental control software. Of course if the kid in question in under 16 and can't yet drive, you the parent have to take and pickup kid to/from library. This isn't really convenient for the parents but works quite well.
So, I might suggest that you take a more active role in his banishment from Internet usage, and don't rely entirely on your router blocking or even parental control software. None of those are 100% effective. Like I said kids are smart. When I had my son blocked from gaming sites when he got his first laptop at about 15; he simply found a neighbor's open wifi connection and downloaded whatever he wanted onto the laptop.
None of my safeguards prevented that one! Took me a couple of months to figure out how he did it. Don't underestimate your kid's ability to think outside the box.
Sorry, I didn't answer your Port question; but you can see that it still might not work 100%.
Best of luck,
<<<BIGBEARJEDI>>>
> the game sites must be blocked at the router. Due to dynamic DNS, and server automatic load balancing, gamesites change their IP address often, and the DNS record is updated with the new IP address. Most carriers update their DNS records every 15 minutes. We have Fortinet fabric security, and we can program the routers to periodically search the current DNS resolved IP address for the list of games, such as minecraft, realmofthemadgod, steam, kongregate and so forth. The routers then block that resolved name, not any one specific IP address. 
