What is BitTorrent and How Does It Work?

BitTorrent is a protocol that enables fast downloading of large files using minimum Internet bandwidth. It costs nothing to use and includes no spyware or pop-up advertising.

Unlike other download methods, BitTorrent maximizes transfer speed by gathering pieces of the file you want and downloading these pieces simultaneously from people who already have them. This process makes popular and very large files, such as videos and television programs, download much faster than is possible with other protocols.

Like most Internet phenomena, BitTorrent has its own jargon. Some of the more common terms related to BitTorrent include:

• Leeches: People who download files but do not share files on their own computer with others
  
• Seed or seeder: A computer with a complete copy of a BitTorrent file (At least one seed computer is necessary for a BitTorrent download to operate.)
  
• Swarm: A group of computers simultaneously sending (uploading) or receiving (downloading) the same file
  
• .torrent: A pointer file that directs your computer to the file you want to download
  
• Tracker: A server that manages the BitTorrent file-transfer process

To understand how BitTorrent works and why it is different from other file-serving methods, let's examine what happens when you download a file from a Website. It works something like this:

1. You open a Web page and click a link to download a file to your computer.
   
2. The Web browser software on your computer (the client) tells the server (a central computer that holds the Web page and the file you want to download) to transfer a copy of the file to your computer.
   
3. The transfer is handled by a protocol (a set of rules), such as FTP (File Transfer Protocol) or HTTP (HyperText Transfer Protocol).

The transfer speed is affected by a number of variables, including the type of protocol, the amount of traffic on the server and the number of other computers that are downloading the file. If the file is both large and popular, the demands on the server are great, and the download will be slow.

Another file-transfer method that you may have heard about is called peer-to-peer file sharing. In this process, you use a software program (rather than your Web browser) to locate computers that have the file you want. Because these are ordinary computers like yours, as opposed to servers, they are called peers. The process works like this:

1. You run peer-to-peer file-sharing software (for example, a Gnutella program) on your computer and send out a request for the file you want to download.
   
2. To locate the file, the software queries other computers that are connected to the Internet and running the file-sharing software.
   
3. When the software finds a computer that has the file you want on its hard drive, the download begins.
   
4. Others using the file-sharing software can obtain files they want from specific folders, that you specify on your computer's hard drive.

In this method, the file-transfer load is distributed between the computers exchanging files, but file searches and transfers from your computer to others can cause bottlenecks. Some people download files and immediately disconnect without allowing others to obtain files from their system, which is called leeching. This limits the number of computers the software can search for the requested file.

BitTorrent is a protocol that offloads some of the file tracking work to a central server (called a tracker). Another difference is that it uses a principal called tit-for-tat. This means that in order to receive files, you have to give them. This solves the problem of leeching. With BitTorrent, the more files you share with others, the faster your downloads are. Finally, to make better use of available Internet bandwidth (the pipeline for data transmission), BitTorrent downloads different pieces of the file you want simultaneously from multiple computers. Here's how it works:

1. You open a Web page and click on a link for the file you want.
   
2. BitTorrent client software communicates with a tracker to find other computers running BitTorrent that have the complete file (seed computers) and those with a portion of the file (peers that are usually in the process of downloading the file).
   
3. The tracker identifies the swarm, which is the connected computers that have all of or a portion of the file and are in the process of sending or receiving it.
   
4. The tracker helps the client software trade pieces of the file you want with other computers in the swarm. Your computer receives multiple pieces of the file simultaneously.
   
5. If you continue to run the BitTorrent client software after your download is complete, others can receive .torrent files from your computer; your future download rates improve because you are ranked higher in the "tit-for-tat" system.

Downloading pieces of the file at the same time helps solve a common problem with other peer-to-peer download methods: Peers upload at a much slower rate than they download. By downloading multiple pieces at the same time, the overall speed is greatly improved. The more computers involved in the swarm, the faster the file transfer occurs because there are more sources of each piece of the file. For this reason, BitTorrent is especially useful for large, popular files.

To use BitTorrent for file downloads, you need to install a BitTorrent client. The most accessible program that I've run with a screen reader is ABC [Yet Another Bittorrent Client].

1. Download and install ABC.
   
2. Check and configure firewall and/or router for ABC (if applicable).
   
3. Find files to download. A good way to do this is to search Google.
   
4. Download and open the .torrent pointer file.
   
5. Let ABC give and receive pieces of the file.
   
6. Stay connected after the download completes to share your .torrent files with others.

After you set up your computer, you're ready to download .torrent files. You can search for the term ".torrent" using an Internet search engine to find sites that offer BitTorrent files.

bt.etree.org is a great site for the legal download of music, videos and books.

When you find the file you want, right-click the .torrent link or press enter on it if using a screen reader, choose "save target as" and save the file in a convenient place on your computer, such as the Windows desktop. The .torrent file, which is a pointer to the actual file you want, will download quickly. Next, double-click or press enter on the .torrent file you saved to your computer. ABC will load and start the download process:

As I mentioned before, the more computers in the sending/receiving swarm, the quicker the download process. If you are downloading a file with only a few computers in the swarm, the transfer speed will be relatively slow.

After the download is complete, leave the BitTorrent client software open so that other peers can download .torrent files from your computer.

Peers using BitTorrent can download only .torrent files from your computer. Once you have a complete copy of a file, your computer becomes a potential seed for that file -- as long as you're still running ABC. Sharing what you have causes speedier BitTorrent downloads for you in the future. You can leave ABC running for a few hours or overnight. Simply close ABC when you're done.

Because BitTorrent handles large files remarkably well, it is especially popular for downloading video files. The Motion Picture Association of America has filed countless lawsuits, causing many high-traffic .torrent download sites to shut down because they were distributing copyrighted material.

BitTorrent itself is perfectly legal to use. When you select a file to download, however, it is your responsibility to make sure the file is not copyrighted.

Torrent2exe

Torrent2exe makes files distributed via BitTorrent downloadable without a separate BitTorrent client.

Here's how it works. You download a torrent file (just the tiny torrent, not the big file it helps you to download) to your desktop, and then upload that torrent to Torrent2.exe. Click the download button, and you'll get an executable file. When you run this program, a standalone BitTorrent program will start up and immediately try to download the source file to whatever directory the executable is in. The site also allows you to enter the URL of a torrent instead of uploading a file from your desktop. But I had less success with that method.

If you want to convince your less tech-savvy friends or relatives to download a Creative Commons licensed movie, Torrent2exe could come in handy. Instead of telling them to download a BitTorrent client, then a torrent file which they have to load into that client, you can just create an executable that you can send to them.

Click this link to visit http://www.torrent2exe.com.

Torrents with Training Wheels

Although BitTorrent's popularity is unquestionable, it is by far one of the more useful and smart file sharing services out there, it can be somewhat difficult for beginners, and even die hard users can run into complications. TorrentRelay simplifies things somewhat. It converts download urls into links which can be downloaded from within your browser without having to install any extra software. Newbies, anyone actually, who doesn't want to have to install more gear on their machine, can enjoy bittorrents without having to install a client. As such, TorrentRelay also works on mobile devices and game consoles. Torrents with multiple files are automatically split up and can be downloaded one by one, useful for getting individual files from an archive. There is one caveat, however; you can only download files up to 400mb in size, any larger and you'll need to download a cliant.

Click this link to visit http://www.Torrelay.com.