I followed the Transmission help on port forwarding and the links to the explanation pages on-line that explain how to set up static IP address, etc. I couldn't get the port to open following all these step-by-step instructions and connection download speeds were dead slow, even though I've a broadband connection. I searched on google and found a link to Lighthouse on one of the Mac forums. Here's a copy of my email to the Lighthouse developer to thank him for getting my port open - it also explains what I did and others may find it helpful:
"Hi,
I purchased a licensed copy of Lighthouse tonight, after some earlier problems with xTorrent (lost a gigabyte worth of downloaded files - so switched to transmission, but dead slow). So I was looking on the internet on Mac forums for speeding up transmission. Went through some complicated static IP and router reconfigs that didn't work. Found Lighthouse linked on a website and downloaded it, buying a license before I'd tried it, perhaps unwisely following xTorrent fiasco.
Anyway, couldn't get it to 'associate' with my router, with reading all the instructions. Error message says "maybe you should up-rate the firmware on your router - Belkin F5D7632-4, but its online site link says it has the latest firmware. Anyway, went through the basic set-up instructions, two or three times, getting time-out error messages for everything I tried. Eventually, I enabled UPnP on the router web-page, although the other protocol was enabled, and this did eventually associate as (UPnP) in Lighthouse. Went back and tried to figure out what was wrong with Transmission port mapping - copied port map number into peer listening port on Transmission preferences. Then I got a permission request from my firewall software, that I'd forgotten about, and allowed that. And up popped the green light saying "port is open" - bingo.
Then restarted transmission, when it had completed port reconfiguration, and it runs at reasonable speeds again. I had to start an 8.5 gigabyte file download from scratch again as my earlier download was corrupted due to an internet drop-off and it wouldn't restart under xtorrent. That's why I tried transmission instead. Anyway, that's another story. Thought you might find the feedback useful for updating possible error messages. Match the port designation under transmission preferences to that allocated by Lighthouse and un-click and re-click the automatic map port option in transmission. Then, if you have forgotten firewall software, like me, it may pop-up with a warning saying do you want to allow this?
I know this is all probably too obvious, but, well it had me scratching my head for a bit and it may help you help others. Its working fine now and I have a chance to download the BBC's ancient Rome series, perhaps before I die. Nothing wrong with me but 8.5 gigabytes at 3.5kb/s would probably take years to download.
After the total non-feedback or help from the xtorrent author, I should say thanks that you've made a good effort at explaining what to try to do in your help file. Even though a novice like me found it difficult to follow when I couldn't get past step 1 - associate with your router. Anyway, its buzzing along nicely now. Thanks again.
Cheers,
Pete"
Lighthouse works fine for me - Macbook pro,OS X v.10.5.6, Belkin router,Transmission v.1.7.4, BTbroadband ISP. I needed to read the Lighthouse instructions (if all else fails read the instructions), but once I got it to associate with my router - bingo - port mapped automatically from Transmission>Preferences>Network> then uncheck - recheck "Automatically map port". Hope others find the feedback useful.
Cheers
Oh, and a URL for Lighthouse:
http://codelaide.com/blog/products/lighthouse