September 01, 2010

How did I connect up?

There are mysteries to bittorrent that I am not privy to.

As I write this, I'm downloading the Shana movie. I found a link to a torrent file on a website that a friend told me about, and right now the torrent has 7 seeds and 11 leeches. I'm hooked to most of them.

But there isn't any tracker. The torrent is flagged red, and uTorrent says "hostname not found". So how the heck did uTorrent find those 7 seeds and 11 leeches? (Presumably once it found the first of them, that one told uTorrent about all the others. But how did uTorrent find the first one?)

Posted by: Steven Den Beste in General Anime at 08:32 PM | Comments (2) | Add Comment
Post contains 112 words, total size 1 kb.

1 I think the link you click on downloads the .torrent file.  That file tells your system where the first seed is located ("IP address x, port y, server path z").  What I don't understand is how your copy of uTorrent found the others.  Does the downloading uTorrent client act as a mini-tracker by keeping track of everyone that has ever downloaded from it, and pinging them occasionally to see if they're still available as other seeds? 

Posted by: ubu at September 01, 2010 08:45 PM (GfCSm)

2 In addition to dedicated trackers, BitTorrent supports distributed hash tables and peer exchange.  When you can't reach the tracker for one torrent, it can ask the peers you can reach for a different torrent if they know anything about it.  Once it finds one peer that knows about the lost torrent, it can ask it for a list of other peers, and so connect to the swarm even though there's no tracker available.

Posted by: Pixy Misa at September 01, 2010 08:56 PM (PiXy!)

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