Hi,

I've been researching the difference between TCP and UDP protocols.
According to what I've read, the basic difference is that TCP is reliable and offers error correction (waits until one packet has been successfully transmitted and only then sends another one), whereas UDP offers more speed but doesn't offer error correction.

My question is: How does it work with torrent clients? what do torrent clients like azureus use: tcp, udp or both? If both, is there a way to specify which one I want azureus to use? Or do they work simultaneously?

thanks

BitTorrent does not use UDP, only TCP.

In general, UDP transfers over the Internet are limited to "throw-away" data, like online games. If a few packets get lost, maybe your character jumps a bit farther than he should have, but the game will continue. Transferring a file on the other hand, that requires everything to arrive intact, so it can't be left to UDP's "machine gun" design (there are some exceptions to this though, as in the case of NFS).