That is the Ident port, it doesnt help with dcc sends at all. You sure you havent dmz'ed the lot to your pc? How else well the recievers connect reach your pc through the router? (unless you got NAPT going and thats got its own problems, on most routers)
I point people needing to understand/do portforwarding to
www.portforward.com And poeple needing to check what ports there PC actually has accessable to
https://www.grc.com/x/ne.dll?bh0bkyd2 which is a port scanner.
Normal ports that need to be forwarded to your pc if sending files are the ones you have set in alt-o/connect/options/advanced/FIRST & LAST
I would keep the number down to 10 total, and not have any pc's using overlaping numbers since the router needs to be told which pc to forward which ports to.