BitTorrent Terms

During the small history of BitTorrent and the configuration of BitComet I have introduced a lot of new terms that may sound strange to you. I'll try to explain all those terms in more detail on this page.

A tracker is the software on a web server that keeps track of the users that are downloading something from a site. It's purpose is only this, to help users talk to each other. The tracker does not send you files, it only created the connection between you and the person that offers the files and the other users that are already downloading the files.

The set of files that are being offered are defined as a torrent, you get information about this set of files through a torrent file, a text file that contains the list of file names, their sizes and some error correction information. The torrent file does not contain parts of the files in the torrent.

In a torrent file, files are split in even size pieces called chunks, each chunk has an error correction code which is stored in the torrent file. This helps you a lot, if a chunk is detected as bad, you only have to download that chunk again and not a whole file or the whole torrent. Chunks are usually between 256 KB and 4 MB. The whole torrent file has another signature called hash which makes it different and unique. This also is stored in the torrent file.

After you download the torrent file, BitComet connects to the tracker and receives a list of other people that are also downloading the torrent. You and the rest of the people are from this moment considered a swarm, a group of people helping each other download the torrent faster.

In a swarm there are two types of users, seeders and lechers. The original user that offered the torrent is called seeder because he only uploads the files in the torrent to others. While you download files, even if you are also uploading parts to other users, you are called a leecher. As soon as you complete the torrent and start to only upload the torrent to other users, you are called just like the original users, a seeder.

There is a special type of leecher, a user that does not upload at all, for various reasons, because he doesn't like to share or because he is behind a firewall or for lots of other reasons. BitTorrent is based around the idea that users help each other by exchanging parts and has a lot of tweaks and algorithms to discourage you if you don't upload. The download speed increases a lot if you upload chunks to other users, this is why you must do the best you can to be able to upload to others.

There are a lot of Internet sites that offer torrent files for download and most have their own tracker to track the torrents files. Some sites do not require any registration and you are free to download anything at your own pace. In change, other sites try to form small communities and because of this they are private, you have to register to have access or you have to be invited by an already user of that site.

Because these small communities often have very interesting torrent files (while not alwas 100% legal), they are faced with the problem of many users downloading the hot torrent files and not helping other users in the community. This type of user downloads the torrent very fast and doesn't stay and help other users download the torrent when download is complete.

In order to encourage these leechers to stay and help other users by uploading files to them, the private sites have some restrictions or advantages, depending on the ratio you have, the ratio being the number of bytes uploaded / number of bytes downloaded. You should always have a ratio over 1, this means you upload more than you download. The disadvantages of having a low ratio can very from forcing you to wait 1-2 days before downloading anything new to allowing you to only download one torrent at a time. On some very private communities, if your ratio drops below a certain amount, for example 0.2, you are not even allowed to download, the only thing you can do is to upload what you have already downloaded.

If you are in a local network with other users that are using a tracker, that tracker can be confused and not count the ratio properly. This is why in almost all trackers that require registration and count the ratio a code called passkey is implemented. This code is unique to each user and is stored in each torrent file you download from that site. You should never share your torrent files with other users. If they're smart, they can extract the passkey from the torrent file and use it in such a way that the tracker will think you have downloaded what they download and you ratio will be affected. If you share your passkey or somebody finds it, you should change it as soon as you can (from your account's settings) or you should contact an administrator of that site to change it for you.

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