UPnP does not block ports. UPnP is a control scheme for peripheral devices, and that’s all it is.
UPnP is basically a set of predefined messages and predefined effects.
A typical UPnP message sent to, say, a printer, might be, “UPNP SAYS TURN YOURSELF ON”, and the printer, if it implements UPNP, knows to listen for that message and turns itself on in response when it gets that message. My printer does this. It’s great, I don’t have to remember to turn it on when I print. Other printers don’t support that PART of UPnP, so they won’t turn themselves on, though they’ll do the rest of the commands.
“UPNP SAYS FEED A PAGE” and the printer ejects the current page, even if its blank.
A printer that does NOT implement UPnP, or does not implement that part of it, gets that message and just ignores it.
So, of course, UPnP can’t block anything or do anything by itself, it’s just messages sent to devices.
One of the kinds of device that it can control are routers or gateways which have built-in firmware firewalls, and those built-in firmware firewalls can block ports. But UPnP itself cannot.
BitComet told you, “your listen port is blocked.” “I unblocked your listen port”. You’re good there, that’s what you want. BitComet tells the windows built-in firewall to open your listen port when BC needs it, and to close the port when not.
Then BC tells you, in effect, “I can’t open the door!” (Door not found)
Well, if there isn’t a door, you don’t need to have it opened. If you don’t have a door, then of course you can’t open the door you don’t have! Doh! But this is what BitComet is telling you.
I couldn’t use UPnP to map a port, because there’s no UPnP device here. Doh!