Difference between revisions of "BitTorrentFAQ"

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A collection of frequently asked questions about BitTorrent.

Questions are from the BitTorrent mailing list and originally posted to this wiki.


Also make sure to check out Biran Dessent's BitTorrent FAQ, IdolCrash's BitTorrent Tutorial, the Bit Torrent FAQ at iAWiki, [1], The BitTorrent FAQ for Little Monkeys] (a very simple overview of BitTorrent). Another good guide is Magoo's Guide to BitTorrent, and it's also mirrored in spanish as Ayuda BitTorrent.

Some topics:

General FAQ:

Q: 'Wasn't there a list here of free BitTorrent sites?

A: It.s at the bottom of the page. See also wiki.etree.org.

Q: 'Is there a bittorrent for FreeBSD, and how can I use it as a background process?

A: Yes, the BitTorrent is available as a port (/usr/ports/net-p2p/py-bittorrent).

Q: 'How can I use BitTorrent from a console or as a background task in Unix/BSD?


Q: 'Files downloading with BT 3.2 are always the size of the finished files, while files downloading with BT3.3 grow until they are the finished size. This presumably means that the file structure has changed between 3.2 and 3.3. Now my question: If I have started a download with BT 3.2, can I upgrade to 3.3 and finish the file this way or will this corrupt things? Thank you.







Q: 'How can I create .torrent files using only the programs in the BitTorrent source distribution, without using a GUI?


Q: 'I want to seed a few files and use the btlaunchmanycurses program for that. But it opens a separate server port for each file and I have to open a few dozen ports in my firewall! Is there a client that handles multiple files via just a single port?






A : Yes it is.

Q: 'This has happened several times already for me. The download is at around 99.9% complete and everytime it gets close to 100%, it reports that a piece failed hash check and that it's re-downloading it. However it just keeps re-downloading that piece over and over again. How do I complete my download?


- This usually results from buggy NAT routers that are replacing legitimate data in your packets. When the packet fails the hash check, because the router scrambled it, BitTorrent rejects it, and asks for the data again. See [2] for more details. And be glad BitTorrent has noticed that your router was corrupting packets -- none of your other software figured it out!

Q: 'Where are the settings/options?

A: For Windows users: Go to run and type "c:program files�ittorrent�tdownloadgui" - this will give you a list of commands.




Q: 'How could I detect if BitTorrent is running on a host using HTTP headers? what would the HTTP query string look like?


Q: 'BitTorrent lags the hell out of my computer. I've got cable and a 2.6ghz processor. When I get like 3-4 or more Torrents going, my computer and connection are very laggy. What's wrong?

A: You're probably maxing out your upload capacity, which affects your download speed because downloads slow down until they see ACKnowledgement packets coming back up. Cable usually has a very large download capacity, around 2Mbit /sec, but a very limited upload capacity, usually 128 to 256Kbit/sec, and often poorly queued. Running a bunch of BitTorrents will rapidly chew up that thin upload capacity causing your network connections to lag (even downloads require your computer to send out some packets). Limit your upload rate to about 75% your upload capacity to allow for overhead, using a client like BitTorrent-4.x or ABC) that consolidate multiple torrent downloads into a single program, and have a global upload limit.

A: I've fixed this on my computer by turning off the Indexing Service. Go to Control Panel -> Administrative Tools -> Services, and turn off Indexing Service there.

Q: 'How can I determine my maximum upload bandwidth, so I can set the max to 75% of that?



A: A few possible reasons:

  • Go ahead and use FTP if you can find someone offering the file for FTP.
  • upload/download rates vary depending how many people are on the torrent, and how much of the torrent they have downloaded. If many people are on a torrent it can take some time before bittorrent finds "local" peers with a good transfer rate.
  • bittorrent can be slow for the following reasons: 1) you start with very little file to offer, and lose out on the "tit for tat" algorithm 2) on torrents with large numbers of downloaders it takes time to find peers with a good connection rate to you 3) only one person has a full copy of the file and they are on a slow connection 4) maxuploadrate is not set and the upload is saturating your modem - 1 and 2 fix themselves if you wait on the torrent for 10-15 mins.
  • If you're uploading more than you're downloading, be happy for all the other guys who you're providing good download performance to. Often this happens when a single seed is slow or is swamped, or if the seed is serving up dozens of files and they're all competing. Your fast upload speed will help everybody else "catch up" with you -- then everyone will slow down to the speed at which the seed can send its unique copy of the data out.

' Recently discovered & verified - Some ISPs are throttling the traffic on the BitTorrent default ports. Changing the ports from the default range to a different range (in the 50000's) changed downloading from a trickle (1-2 kB/s) to The Way It Should Be (up to 330 kB/s on a 3000/256 connection). This almost seems unethical, but ISPs have probably taken note that BitTorrent traffic has become over 50% of Internet traffic by some surveys. BitTorrent also saturates the 'slow' side of asymmetric connections with it's uploading, which upsets the 'surf and download' usage the cable modem providers are expecting from their typical user. Name names here: what ISP did you verify this about?*

    • ONO in Spain (now Auna) is currently doing this; they even managed, after much pressure, to acknowledge heavy handed QoS on P2P traffic.
  • You can tune BitTorrent by increasing your upload limit slowly from about 75% of your maximum and finding the point where your download speed begins decreasing instead of increasing (best done on a torrent with many seeders). That peak is the best setting for your upload limit.
  • Your router may have to foward the ports to a particular IP address. You can determine your IP address under windows using the "ipconfig" command. However, your computer may be assigned a NEW IP address whenever it reboots. If your Torrents suddenly slow down, confirm your computers ip address matches the one your router is fowarding too. (A typical home router IP address will look like "", "", etc.)

Q: 'Is there any way to cloak your IP address while using the torrent program?





A: There already are several efforts underway in other projects, the most prominent being [3], [4], and [[P2P-Radio|Streamerp2p]]. They use a similar idea to BitTorrent in that 'clients' can also become 'servers', but the model is different because the clients generally just help retransmit the feed they are receiving from an upstream server.


Q: 'Is there any way to limit the bt download rate. I have a co-located machine on a 100Mbit connection, but with a contracted rate of 2Mbit (I pay extra for large bursts) when I started downloading Mandrake 10 the download rate jumped to 10Mbit (I had to stop the download before it cost me a fortune !)

A: BitTorrent clients play a tit-for-tat game with transfer rates; if you tell your client to limit its maximum upload rate, that will make its peers limit the rate they download to you at. If you start off with a very conservative upload rate and watch your connection's behavior, you should get a feel for a safe upload rate limit. This will work unless there are a lot of seeds, which download to anyone despite not needing any uploads.

A2: Brian Dessents' [[BitTorrent FAQ]] lists ways to limit the download speed. Essentially you need to use a firewall, traffic shaper or some other utility to limit the download speed.

Q: 'If a .torrent contains more than one file, is there a way to download only selected files?

A: Yes, I saw it in BitTornado (maybe some other clients do it). Start your download and go to "details". Right click a file and select "download never" to exclude it. Tested with Linux but I hope BitTornado works the same way on any OS.

A: Azureus (java/gui client: http://azureus.sourceforge.net/) has the exact same feature, although i haven't tested thoroughly.

A: BitComet also has this feature, just uncheck the box next to the files you don't want to download when the "Properties" box shows up when starting the torrent.



Q: 'Some of the pc-games are in a wierd format. So how do you get them to run?

A : Try checking http://filext.com/ to see what program is associated with the extension of the file, hopefully this will help you. The files you got may possibly be a CD image that needs to be burned to a CD using the appropriate program (ISO, BIN/CUE, other proprietary formats), or may be archived/compressed (zip, RAR, 7zip).


A: Aliens.

Q: I'm downloading a torrent containing many files. I just want the first file, so it to high priority, and the others to "do not download". After a while this file is 90% down, but now when I start the bittorrent client (Azureus) it sits there uploading to other people but not downloading. I can see seeders with 100%, but my client doesn't request any files from anybody, even over the course of an hour and uploading many megabytes. As soon as I set all the other files to be downloaded the data starts coming in. Why won't it request any more of the first file?

What places are recommended in searching for .torrent files?

A Few Sites:

See also wiki.etree.org.

There are also BitTorrentSearchEngines.

For BitTorrent News