A little question about trackers

[woxenrud]

Im still new to torrents and stuff and have been messing around with bitcomet to see how everything works.

I noticed that these "trackers" are different on different torrents. for example

torrent 1 have:

http://tracker.thepiratebay.org/announce

udp://tracker.thepiratebay.org:80/announce

udp://tracker.openbittorrent.com:80/announce

http://tracker.openbittorrent.com/announce

while torrent 2 have those four plus:

http://tracker.publicbt.com/announce

udp://tracker.publicbt.com:80/announce

I then tried to add those two to the first torrent and i saw that the connections increased.

Does this mean that the more trackers a torrent have, the faster it downloads? Am i supposed to have a big list with trackers and add them to the downloads i start?

If someone gave me some info here i would be very happy :)

[kluelos]

No, it does not mean that at all, but some misguided souls think so.

Several of those trackers don't even exist. This is a common dumbness, so you can be an evangelist. See those lines that start with "udp"? Most tracker sites DO NOT HAVE UDP-based trackers or options. Among the major sites, only Demonoid even has one. The µtorrent client does not support UDP at all.

Some ... people ... seem to think that, well, maybe someday they might be added (why???) so I might as well add in a url for it. This is just a waste of time.

In this particular case The Pirate Bay took its tracker down and no longer has one. It relies solely on DHT, PEX and magnet links.

More trackers don't do a thing for you except add to the load of those other trackers. You downloaded this torrent from somewhere, doesn't matter where. Somebody else downloaded it from someplace else, again doesn't matter where. Both of you got the same tracker list, both of you contacted the same trackers, both of you got the same list of peers from each of those trackers.

Getting the same peer from this list and from that list doesn't do anything except waste the tracker's resources. For you and him it's just a duplication, and DHT adds a third duplicate. But you're only going to make one connection to each other, more connections are neither needed or allowed, and if they were, you still wouldn't need multiple lists of the same peer.

If there was only one tracker listed, the effect and your transfer speeds would be exactly the same.

People who create torrents this way don't understand what they're doing. That happens a lot in bittorrent.

[Guest EvgenyS]

I knew it.

But UDP-trackers? I have always been to assume that "UDP" means something "auxiliary" to the main tracker... Now, you said there is no any support/profit to type it into torrent properties. So, is it advisely to remove every udp-named trackers of each torrent when encounter? Just to free up some BitComet resources?

Edited July 16, 2010 by EvgenyS (see edit history)

[greywizard]

It's not worth that much the trouble of removing them either, I guess.

UDP being a connectionless protocol, all that BitComet does is send an UDP datagram to the specified URL. It doesn't have to set up a connection first as in TCP's case.

If it gets a reply it's OK but if there is no server at that address it doesn't get a reply and it's OK too.

You may say that it will free up some little memory space and CPU cycles occupied by the count-down timer for connection retry. But at the processing power and memory amounts system have these days, that would probably be insignificant.

But if you have nothing better to do than combing every torrent you add to your list, go for it.

It is pointless to add them to the tracker list unless you know for sure that there is a server running at that address which tracks that torrent and it's an unrewarding pain to seek and remove them as well. Unless you're doing it for fun. ;)

[kluelos]

what you get from a UDP tracker is exactly the same as you get from a TCP tracker. The bittorrent protocol and the metafiles clients and trackers exchange and can understand, are all rigidly defined and in the public domain. There's nothing auxiliary out there.

Think of a radio station that broadcasts exactly the same thing, on AM and FM. It doesn't matter which one you listen to, you're going to hear the same thing on either one and listening to both at once does nothing for you. Neither does having TCP and UDP trackers.

[Vasy]

There is a little advantage in having multiple trackers... Some of them might time out, and if you have only one you'll have to wait until it comes back to get a new list.

Still, you've got other alternatives like dht, pex, lt-seeds, eMule if the torrent does not have the "private" flag. In that case you rely on the trackers alone to get that list.

But all this will not stop you from continuing the task, as BitComet still has the last list of peers to work with.