I would say yes when it comes to defaults or standardized settings for ports. Whether you're trying to configure a netplay match with Hisoutensoku or trying to fix your firewall so others can join you in a game of Defense of the Ancients, this knowledge tends to be critical to actually playing a game. Often times it's already filled out when you look at the game's netplay menu, but that has rarely stopped a question being asked. Many net-gaming communities stick to the defaults because it is both well established and requires no extra fiddling.
And remember that "There is no default/standard port" is a very real answer, and should be given as such as opposed to being left as a comment and voting to close!
Any deviation from this is specific to the scenario and community in question, and any questions should be asked within that community. And expectedly so - you're being a part of that community in order to know that it is different!
Going past port settings and into general installation questions, I think that as long as there aren't any other outstanding issues with the question (I'm referring at least specifically to this, which is still in debate), then we can allow these. They're not much different than the many questions we get about [steam], as long as we're still in the confines of the game. "How do I configure the port settings on a NETGEAR router", for example, would be off-topic (I think it fits on SU but you'd've to ask the SU people about that) because the fact you're configuring the router for gaming is irrelevant to the answer.
