BitTorrent FAQ
This small FAQ explains some of the questions rised by BitTorrent -- the P2P content distribution system.
Contents
- What is BitTorrent?
- Where can I get BitTorrent?
- How do I install the client?
- Why does it take so long to start a big download?
- The file size looks complete, but the download keeps running. Why?
- Can I resume an interrupted download?
- How can I be sure the downloaded file isn't broken?
- Why should I leave BitTorrent running after the download?
- How can I stop BitTorrent from uploading?
- Is BitTorrent safe to use? Does it expose my computer or files?
- Where can I find .torrent files?
- Does BitTorrent work through firewall or NAT?
- How do I make my own torrents?
What is BitTorrent?
BitTorrent is a content distribution system that distributes the downloads among peer downloaders. In essence when you're downloading with BitTorrent, you are simultaneously uploading the same file to other downloaders. While there is an official "BitTorrent" client created by the creator of the actual system, there are many other clients available as well that use the BitTorrent system.
Where can I get BitTorrent?
You can download the official BitTorrent client here at AfterDawn: BitTorrent v6. However, there are two other clients that I would recommend highly and those are ”Torrent and Vuze (Azureus Java BitTorrent client). We have full guides for each here on Afterdawn and I will post those later. For now though, you can get those clients here:
”Torrent v1.6.1.- You may be wondering why I have not linked to the latest build (1.8 as of writing) and that is because in late 2006, BitTorrent Inc. purchased ”Torrent, which led many to believe that the MPAA and RIAA were now watching. You can read more about the acquiring here: BitTorrent Inc. acquires uTorrent (December 6th, 2006)
Vuze (Azureus Java BitTorrent client) v.4- Get Vuze here.
Installing BitTorrent, uTorrent or Vuze couldn't be simpler. Just download the installer and run it. For Vuze you may need to update to the latest Java if you have not already. There will be no icons to be seen in either Start menu or desktop. The clients will ask to be associated with .torrent files and launches them automatically when you download or open them.
Torrent clients will allocate space for the file to be downloaded before actually starting the download. That means that the client writes a "dummy" file that has the exact size of the file being downloaded, just filled with zeroes. In newer versions however, the wait time could be seconds, even for larger files.
The file size looks complete, but the download keeps running. Why?
See the question above. The file isn't complete until the transfer meter has reached 100% and your client tells you the transfer is complete.
Can I resume an interrupted download?
Yes. Just open the .torrent again either by double clicking the file on your HDD, if you saved it there, or clicking the link again on the web page. Then point the download to the same exact directory you started downloading to -- your client will automatically inspect the already downloaded file and resume downloading.
Your client will check downloaded parts using cryptographic hashing (SHA1). When the download is complete, it is also completely verified and OK. If it isn't, then the original file was already corrupt and you should try from a different source.
Why should I leave BitTorrent running after the download?
It's considered a good practice to leave your client running even after your download is complete -- if everyone closes their downloads there will be no "seeds", or complete downloaders to download from. To upload after the file is done downloading is called seeding.Please try and leave the client running at least until your "share ratio" is 1.0 or more, i.e. when you have uploaded at least as much data as you have downloaded. If you are using a private tracker, you may even get in trouble if you do not seed a 1-to-1 ratio or keep seeding for 3 days. For more information on seeding please check our glossary term: Seeding, leeching, and the importance of sharing.
How can I stop BitTorrent from uploading?
All the aforementioned clients will allow you to adjust the rate at which data is being uploaded to other users. However, there is little point in doing this, since most clients determine the amount of data you receive by the rate you upload at. If you don't upload at all, your transfers will slow down to a crawl, as you will be throttled.
Is BitTorrent safe to use?
Absolutely. It only uploads the file you are downloading. It has no access to your private files, and it doesn't expose your computer or your private data to the outside world. However, if you choose to share unauthorized files, you may be subject to prosecution if proven.
Does BitTorrent work through firewall or NAT?
Yes, but it works faster if other peers can connect to you. It is best to select a random port to open over the 50000 range. The ports 6881-6890 have been blacklisted by all clients and networks so please do not try those.
How do I make my own torrents?
Serving files over BitTorrent is a bit more complicated, and won't be covered here. In essence you need a tracker to announce the torrent, and a web server to host the .torrent -file itself. Many public trackers however, such as Mininova, The Pirate Bay, and TorrentReactor, will host the torrent file itself, with little effort on your part.
Version history
v2.0 -- 1st December, 2009, Full layout change, revision to bring this FAQ up to date, added cross links, related guides, keywords. (Andre "Dvdback23" Yoskowitz)
1.0 - Initial version - 030625 - JK
Written by: Jari Ketola
