Seeding to Peers w/ Firewalls

[philbar]

This doesn't really have anything to do with utorrent but is it possible create a torrent server (one that just seeds files) that is able find and connect to peers that are behind a firewall which cannot normally connect? Using bittorrent, is it possible to get high speed downloads from a torrent server even if behind a firewall and to somehow program that server to only look for peers that cannot connect to the rest of the swarm?

I want to set up a system of distribution that allows people behind firewalls (university, work...) to still be able to download using bittorrent even if they can only connect to a specialized torrent server?

[Lord Alderaan]

If you are connectible people who are unconnectible should be able to connect to you. Whether u can program a client to only allow connections with unconnectible people is a different matter. It should be possible if u know the protocol and a program language that can implement it but its outside the scope of µtorrent.

[Switeck]

As is, people who are firewalled cannot connect to others who are firewalled. In short, they are NO help to one another! Only unfirewalled people can ever connect to firewalled people -- and then ONLY if the firewalled people try to connect to the unfirewalled people first. If the unfirewalled ones try to connect to someone firewalled it always fails.

Put more bluntly, a torrent with 10 firewalled peers+seeds on it and no one else is DEAD.

This is why you don't want to be firewalled yourself if you can help it.

...and just think, alot of people are too lazy to unfirewall themselves.

[philbar]

The reason I ask, is I am developing a system to distribute files (which people purchase from a store) with p2p but I don't want to leave people out of buying if they are behind firewalls (school, work, computer illiterate...).

[Switeck]

Then share them from unfirewalled fast source/s. Firewalled connections that aren't locked up tight can still download/upload to not-firewalled connections...but the firewalled connections have to "CALL" them first.

[philbar]

Is there a way to prioritize seeding to those behind firewalls?

[Switeck]

No, though you could "priortize" the reverse: seeding ONLY to non-firewalled ips by being firewalled yourself.

If too many people are firewalled, your lone seed ends up acting more and more like an FTP site with no mirroring. And there's nothing you can do about that except to state unfirewalled people get faster download speeds...and hope that catches on.

[Lord Alderaan]

philbar. Yes, by writing your own torrent client. It cannot be done in µtorrent or any other client for that matter.

Maybe a client that supports plugins (like Azureus) but that depends on the extend of the power a plugin has in that app.

But my advice is don't do this. It hasn't been tested but theoretically its better to get a couple extra seeders (that are actually connectible and can seed to everyone decently including unconnectibles) fast then to try and boost the unconnectible speed all by yourself. Besides this boosting is only short term and will go at the cost of virtually stopping traffic to connectible people. Which in the end means everybody will need days to download anything.

Just explain that if someone is unconnectible downloading your software will take a longer time then connectible people.

[Switeck]

Another thing that could be done if writing your own specialized client is implimenting UDP-based NAT transversal hole-punching. It will resolve many of the router-caused firewalled issues. However many consumer products cannot handle high UDP packet rates, and you'll essentially have to recreate TCP error correction over UDP.

Limewire has documented sourcecode for UDP-based NAT transversal hole-punching, but it's written in JAVA.