BitTorrent : Java Glossary

Firewall

Installing

You may have to set up as association for your browser to tell it to execute *.torrent files with the default handler.

When you click on a BitTorrent link, at first it appears nothing happens. Give it 10 minutes or so to get going.

Remember to configure BitTorrent with the ports you have opened up in your firewall.

BitTorrent is frequently updated, so you might check every month to get the latest software.

Under the Hood

BitTorrent then is only useful to deal with a popular single download. It is not like Napster picking files off other people’s disks they have previously downloaded. Downloads are huge, typically an entire CD or an entire movie, usually 700 MB to 1500 MB. BitTorrent is especially popular for distributing Linux distributions as iso CD images.

The torrent files arrive and automatically unpack themselves into a set of files in a directory. However, sometimes they will arrive in compressed form, and you will need to run a decompressor such as WinZip, PkUnzip, WinRAR, 7Zip depending on the extension.

The BitTorrent algorithm works in such a way that the longer you stay connected the faster you download. This is because you have more of the file to trade with others for parts they have. Unlike ordinary downloads, nothing much happens for a long while after you first start the download. You start as a beggar, in BitTorrent terms a leech, and gradually work your way up in status to a seed when you have the complete file, and stay connected out of altruism just to serve others with it. This progression happens automatically. You don’t have to do anything other than stay connected.

Creating a bundle of files for others to download with BitTorrent is called making a Torrent. You can use the makeTorrent utility or the Make new Torrent option on the BitTorrent client.

To serve BitTorrent files, you need an ordinary HTTP server that is configured to deliver the application/x-bittorrent MIME type. You upload the tiny *.torrent files to your website and reference them in your webpages. You also need to package your downloads as *.torrent files, containing embedded SHA-1 digests to detect errors. You also need to start one or more trackers that orchestrates the flow of traffic between multiple people downloading your files. The trackers don’t know who has which pieces of the file. They just make introductions between the various parties downloading each file. BNBT and CBTT are names of common BitTorrent tracker toolkits. The peers announce what they have to each other. This requires a tiny amount of bandwidth. It is also possible now to use BitTorrent without a tracker server. There are two incompatible schemes for every client to act as a tracker: Azureus and BitComet. For trackerless torrents, you use the DHT option when creating the bundle. If you don’t have a server to run the tracker, you have to use the URL of the tracker server you plan to use, e.g. http://my.tracker.com:6969/announce. The tracker overhead of serving a torrent to the world is minuscule, about 1/1000 that of serving a single HTTP download. You still need to leave at least one seed running somewhere on the bundle. Oddly, any tracker could manage any bundle that contains its URL. The tracker server does not need to be configured with a list of bundles to serve. So likely you will use somebody else’s tracker server.

There is a requirement to set up an endlessly-running dummy seed downloader for each file that has also has a complete copy of the file. This is needed because the tracker does not have a copy of the bundle. The way files are served with BitTorrent clients. There is no special way to serve the master copy.

The net result is, you can serve BitTorrent from your website without anything special other than setting up the MIME type for .torrent files to application/x-bittorrent. You need a PC dedicated somewhere, running client BitTorrent with all your bundles.

The BitTorrent docs tell you mostly how it works inside not how to use it, which is pretty confusing to a newcomer. The newbie does not understand that all this talk of leaching, sharing and tit for tat, has nothing to do with his behaviour, just a model of how the program works inside and how it works to combat pirates using the same protocol.

Unfortunately, BitTorrent files don’t seem to come with a built-in synopsis of what the file is. You have to download the whole thing to find out what it is.

There are a number of BitTorrent client implementations. The official one forgets your download directory and makes you navigate to it every time. It does not tell you anything about what other clients are doing or even if there are any.

BitTorrent is quite a bit slower than ordinary downloading, because your download speed is limited by other ordinary users upload speeds. Some may even be on dial up. The torrent is in the aggregate flow. The paradoxical feature is that the more people download a file at once, the faster the downloads go. BitTorrent works because altruistic (or perhaps just inattentive) people leave downloads running after they complete, donating upload time to others. Usually you set BitTorrent going and then go to bed and come back in the morning.

BitTorrent can take quite a while to get started before it picks up steam. right click Start Download, then be patient. It can just sit there apparently inert for 10 minutes or so before it gets rolling.

Downside

The frightening weakness of BitTorrent is an 8 hour download can pack it in if the seed PC goes south or its owner turns it off or the tracker server shuts down. You don’t even get a message that this has happened, though there are some hints in the log. If you leave the download running it might eventually recover when a seed, not necessarily the original owner’s, restarts. A partial download is not useful since it contains holes, not just the tail chopped off.

*.torrent files don’t contain a proper description of the bundle. You often have no idea what platform or format the file is. You don’t even know if is audio, video, software, or text. The directory of files gives some hints, but it needs a proper descriptor with standard fields to facilitate searching.

You have to download the entire bundle before you know if you have got what you wanted. You may have totally the wrong thing or a file in a format your machine does not support. There need to be a scheme to include a trailer or sampler than is downloaded first.

BitTorrent is very slow to get started. The problem is it is very concerned about counterfeit BitTorrent clients behaving in a greedy fashion and in the process, it wastes a lot of time, though not bandwidth.

BitTorrent client won’t tell you if it has successfully negotiated the firewall and what ports it is using. Perhaps other clients do.

Often there are several possible trackers to use. There should be a way to automatically join the one with the most activity.

BitTorrent Download Sites

BitTorrent Upload Sites

BitTorrent Recommended Downloads

• Italian TV did a documentary on the American use of white phosphorus on the citizens of Fallujah. You can play a low-res version of the movie online . You can download a higher quality version of the movie with BitTorrent in either Microsoft or Apple QuickTime format 
• Loose Change: Video evidence the three World Trade Towers were taken down by a controlled demolition and that the Pentagon was not hit by an highjacked plane as claimed. Download the DVD with BitTorrent or order the DVD 
• Power Of Nightmares: BBC documentary video on how politicians manipulate the fear of terrorism

Fahrenheit 911

	recommend DVD⇒Fahrenheit 9/11
	DVD
	by: Michael Moore
This documentary on DVD is fun, entertaining, and light. It allows Bush to hang himself simply by showing footage of him. VIewing this film is the fastest way to disabuse someone of their notions that Bush is an admirable guy. I strongly suggest you buy a copy and show it as many people as possible as soon as possible.
amazon.ca amazon.com chapters.indigo.ca powells.com amazon.fr barnesandnoble.com amazon.de amazon.co.uk

• How to BitTorrent a copy of Fahrenheit 911
• IsoHunt
• onlinepuzzles.net