[bittorrent] BitTorrernt and clients behind NAT & Firewall (newbie)

Thomas Tuft Muller ttm at online.no
Sun Apr 9 10:39:11 EDT 2006

BitTorrent experts,

I've just configured my own tracker (EasyTracker) and initiated a private file sharing network with friends. It seems to work fine and dandy. We're using ABC BitTorrent clients. My questions/comments are generic though. 

If a client is behind a firewall and no port forwarding is set up, no peers can connect it, but as far as I understand my client is still seeding (upload speed > 0.0). How does this work? Is it somehow proxied by the tracker, or by the peer(s) my client is connected to to download files?

Configuring port forwarding correctly is obviously important for sharing files, and (at least in Europe) lots of people have wireless routers with built in firewalls but no clue or understanding of port-forwarding, NAT, or fixed IP adresses behind the firewall. I think I read somewhere that about 70% of BitTorrent users don't accept incoming traffic to 6881-6889 and are not contributing to the network. Given this fact, wouldn't it be an idea for the clients to encourage the user to configure the fw correctly? The tracker could check the port of any client and report back to the client when it makes reqeusts to the tracker that it can't reach it on the port it announces sharing on. This message could be translated into a serious "warning" to the user. Is this a bad idea? 

Any input would be much appreciated.



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