Does it help rtorrent to open ports on the NAT router?

[massysett]

Sometimes I see information telling Bittorrent users to open up ports on the firewall or NAT router. Other clients claim that they perform well even without open ports.

I use rtorrent. Right now it says it's listening on port 6961. I haven't opened that port on my router. Despite that, rtorrent has uploaded 6 MB of the new Kororaa Xgl live CD. The current download rate is 77 KB; upload is currently 0.

Even though rtorrent says it's listening on 6961, doing an "nmap localhost" doesn't show anything at all listening on 6961 or any of the 6000 ports.

Does it help rtorrent to open ports? How are other users downloading my torrent if I don't have the port open on my router and nmap doesn't show any ports at all open for listening?

Thanks.
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Draft Windows-to-Linux Guide

[Raptor911]

it does help
but for popular torrents you can get away with being behind a NAT
what happens is if you dont have open ports you can ONLY connect with people who do have open ports while people with open ports may connect with anyone
so, in short, its good for you, its good for the network, but some times you cant tell the difference

[massysett]

But if it helps, why does it seem that rtorrent is not listening on a port at all? At least that's what nmap says. Furthermore, how am I uploading material even though I didn't open ports on the router?
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Draft Windows-to-Linux Guide

[Raptor911]

tcp connections are two way
you may connect out thought your NAT, and with that connection you may upload or download or both

[massysett]

What's the saying? Problem between keyboard and chair? By default nmap doesn't scan all ports, just something like 1670 ports. Doing

[Raptor911]

you can also use

netstat -an

[CrazyTerabyte]

Maybe this explains better: http://bt.degreez.net/firewalled.html

Found this link from bittornado page.