Everything You Wanted to Know About BitTorrent and Didn’t Know to Ask

BitTorrent has been around for over six years and it seems many people do not really understand it or even know what it is. Many people mistake it for the same thing as Limewire, KaZaA, Napster or some other peer-to-peer (P2P) network. If you know someone who’s eyes glazed over when you mentioned BitTorrent, send them a link to this guide. Even if you have a good working knowledge of BitTorrent you may still get some good information here. Feel free to skip to the section that interests you if you are a person in the know, when it comes to BitTorrent.

What is BitTorrent?
BitTorrent (nicknamed Mainline by some developers) is used regularly to share movies, TV shows, personal videos, mp3 files, PDFs, open source software, large files and just about any other digital file. BitTorrent is even used and endorsed to distribute movies, TV shows and music from Hollywood studios and TV networks such as Fox, MTV, Spike, Playboy, Paramount, MGM, WB, Starz, Lion’s Gate, and Comedy Central. Content can be purchased (some are free) thru the BitTorrent website.

The legality of BitTorrent would probably depend on what is being shared, not BitTorrent itself, as there is a lot of public domain material, personal files and even paid content distributed using BitTorrent. Since I am not a legal expert I will leave that to someone else.

BitTorrent is not the same as P2P networks like Limewire, KaZaA, Napster, Gnutella, FastTrack, or Freenet. BitTorrent is not a network, it is a protocol (rules and descriptions of how to do stuff) designed for transferring files efficiently. The software used to download files using the BitTorrent “protocol” are called BitTorrent clients. BitTorrent is actually quite easy to use and works a bit differently than the other P2P networks I mentioned above.

What BitTorrent is in a nutshell is a protocol that allows for a fast method of downloading files being shared among users. What makes BitTorrent different is that it allows for sharing of files across all users who have downloaded and importantly, are in the process of downloading a file. You are not sharing directories on your computer with other users sharing directories.

How does it work?
Peer-to-peer (P2P) by nature has users directly connecting to each other. What makes BitTorrent different is it distributes files in many small chunks. Users do not need to have downloaded the entire file before starting to share it. Sharing with others starts as soon as even a small piece of the file is downloaded. Users should upload (transmit outbound) at the same time they are downloading (receiving inbound). This makes BitTorrent fast and also makes it extremely good for distributing large files. BitTorrent has the ability to pick up where it left off, if your connection is interrupted, making it a good method to download large files.

BitTorrent does use a central server, called a tracker which manages connections between peers (users downloading files). The server (tracker) does not have any knowledge of the actual contents of the files being distributed, therefore a large number of users can be supported with relatively limited tracker bandwidth. Network bandwidth is utilized as efficiently as possible by design in contrast to other file transfer methods.

How does BitTorrent differ from other P2P file transfer networks?
The typical method used for downloading files on the Internet is the client-server model. You simply download the file you want from a central server. This is exactly how both http (web - Hypertext Transfer Protocol) and ftp (File Transfer Protocol) work.

The downside of this you need a direct path to the server and all the bandwidth used is on that path. This method is not very good if the file on that server is very popular or very large. Many people trying to download a file at the same time on the same alloted bandwidth causes a huge slowdown as the server would be forced to deliver the entire file to each user (client). The server resources and cost of bandwidth to distribute such a file is totally on the lone server and its connection. The concept of mirrors partially addresses this shortcoming by distributing the load across multiple servers. But it requires a lot of coordination and effort to set up an efficient network of mirrors, and it’s usually only feasible for the busiest of sites. Also the server(s) must contain all the files that users are requesting stored on it.

Peer-to-peer (P2P) networks such as Limewire, KaZaA, Napster, Gnutella, FastTrack, or Freenet allow users to trade files by directly connecting one-to-one. Files can be shared without having access to a central server with little accountability for the contents of the files being shared. Users are basically downloading a file from a single source, another client or peer (some newer P2P networks do allow file from multiple sources for higher speeds). The sharing is built on the good will of the users sharing directories, if they do not share there is no file to find. The sharing on these type of P2P networks can have significant overhead and can limit the amount of users (peers). If the peer you are downloading from goes offline, sometimes you are stuck with an incomplete file that you may have to start over again to find.

With BitTorrent the more popular a file is the easier it is to download it. Popular files usually mean that more users are downloading the file while simultaneously uploading (sharing) the same file. This makes for a faster download for all and leads to a better distribution of bandwidth. If one or more of the users you are downloading from go offline, your BitTorrent client just keeps on downloading as you are only getting small pieces of the file from other users. This makes BitTorrent very good at downloading large and especially popular files.

BitTorrent users that have complete files and are still sharing are called seeds. Users that are downloading while uploading are called peers (or sometimes leeches). When you are downloading a file with BitTorrent you are usually receiving small bits from the other peers and seeds simultaneously. This means peers, users who do not already have to complete file, are sharing with other peers before their download finishes, unlike other P2P networks.

How do you use BitTorrent?
In order to use BitTorrent to download something, you need to first find the torrent file (.torrent) for the content you want. This torrent file does not contain the file or files you want to download. It is instead a relatively tiny text file that contains all the information needed to allow your BitTorrent client of choice to find peers (other users) who are also sharing and downloading the same file you want.

Once you download this small torrent file, you load this into a BitTorrent client and it will locate the file or files you want to download. As soon as you start to download your file, you will usually be sharing it with others, as it downloads it is also uploading sharing it with other users.

BitTorrent Clients
In order to use BitTorrent to download anything you need to install a BitTorrent client on your computer. There are many BitTorrent clients available for nearly all computer platforms. Most are free, some are shareware and may offer additional features. There are so many flavors of BitTorrent clients, it really comes down to personal taste. Some clients are slimmed down for simple downloading at the fastest speed and some clients are full features applications that allow for searching for torrents inside the application, viewing videos, adding to iTunes or another app, scheduling and help with uploading torrent files. Here are some suggestions which I am sure might not include everyones favorite.

Windows:

Mac OS X:

  • BitTorrent OSX, Free.
  • Transmission, Free - is my current Mac favorite maintained by the same people as Handbrake.
  • Xtorrent, has built-in torrent search $26 for Pro version.
  • Tomato Torrent, Free - an old simple favorite I no longer use.
  • Bits on Wheels, Free - older client.
  • Vuze (Azureus 3.0) - Free
  • BitRocket, Free - is a brand new native BitTorrent client for Mac OS X.
  • Opera (version 9), Free - cross-platform browser has implemented a very simple, built-in BitTorrent client.

Linux:

It is worth mentioning that there are some Firefox Add-ons that can help with finding torrent files.

There are plenty of other BitTorrent clients. I suggest if you are a beginner try uTorrent if you are on Windows, Transmission if you on OS X or KTorrent if you use Linux to start.

How do you find torrent files?
As soon as you install a BitTorrent client you will need to download a torrent file to start downloading a file. So where do you find these I guess you are asking. Well you just search the Internet for them. You can use Google or Yahoo to search for a good torrent file. Just type in what you are looking for and include the word torrent. Google, Yahoo, or your search engine of choice should give you results for torrent files for what you are looking for. Then just download the small torrent file.

There are specialized places or sites to search for torrents. Many of these list all types of files and allow for searching for whatever you may want.

Disclaimer: I am not endorsing or have with any affiliation any of these suggested sites. They may (and in most cases do) contain copyrighted material. Downloading this material without the copyright holder’s permission may be illegal in your country. I do not endorse or suggest that you should download copyrighted material. Proceed at your own risk.

Here is a list of places to try:

Try to find a good torrent file using a high amount of seeders (sometimes labelled ‘S’). The higher the amount of seeders, the faster your download will be. Some torrent sites provide a “health” meter, which is generally a measure of seeders vs. active downloaders of a particular file.

Start Downloading
After downloading a good torrent file, open it in the BitTorrent client you have installed (see list above). You can “add” the torrent file in your BitTorrent client usually by just choosing File -> Add Torrent or just dragging the torrent file into the client’s window. If the torrent file is associated with the client application, simply double-clicking may “add” the torrent file.

The BitTorrent client may ask you where you want to save the file(s) on your hard drive. Pick a location, hit OK, and your file will begin downloading. The speed may take a moment until it to ramps up to full speed. If not search for another torrent with more seeders. Also check below for some tips to speed your downloads.

BitTorrent fully supports stopping and later resuming downloading a file. If you cancel a download before it’s finished downloading, the partial download remains on your hard drive. To resume the transfer, just click on the same torrent link again, select the same location as last time. BitTorrent will see that the file exists and check it to see how much has already been downloaded and pick up where it left off. This is especially goo if your computer temporarily loses its Internet connection or needs to be rebooted for some reason.

Tip: Xtorrent - OS X only, one of my favorite BitTorrent clients. It has built-in search making finding torrents a snap all in one application.

What files am I sharing or uploading?
There is no “shared directory” as with other peer-to-peer applications. Generally while you are downloading a particular file, you are also uploading that same file at the same time. The parts of the file(s) that you have already downloaded are uploaded to other peers. Once you click to remove a torrent you have downloaded or close your BitTorrent client you are no longer sharing it. It is considered being nice to leave your BitTorrent client uploading after you are finished downloading for awhile. This is the normal way BitTorrent shares and gives back to the community.

If you have a certain file (or files) that you want to make available to others, you must first create a .torrent file and upload it to a server, and then seed the file. More about this later.

What do these things mean? Learn to speak BitTorrent

torrent
The small file that contains metadata you (.torrent.) that the information about the file or files you want to download, not the file or files itself. This is the file you need to use with your BitTorrent client to start downloading the file you want. You can save a torrent file to your local system, and then click on it to open the BitTorrent download. This is useful if you want to be able to re-open the torrent later without having to find it again.

tracker
A server on the Internet that acts to coordinate the action of BitTorrent clients. When you open a torrent file with your BitTorrent client, it contacts the tracker and asks for a list of peers to contact. Periodically throughout the transfer, your client will check with the tracker, to “track” how much has been downloaded and uploaded.

If a tracker is down you will be unable to connect. If a tracker goes down after you have already connected and are already downloading from peers, you will be able to continue with those peers, but no new peers will be able to contact you. Many times tracker errors are temporary, just waiting with the client open your download will usually continue.

private tracker
A private tracker is a tracker which restricts who can use it, usually requiring registration of a user account. Private trackers usually register how much the users upload and download and may enforce a minimum upload-to-download ratio. As a result their torrents usually offer better availability and speed compared to public trackers where leeching is more common.

Many private trackers are implement “Passkeys” in the torrent file, which gives each user a specific address to contact in order to get a list of peers. This helps to prevent unauthorized distribution of torrent files from private trackers.

index or indexer
An index is a website with a list of .torrent files usually including descriptions and other information about the content of the files. A tracker is different from an index by the fact that it does not necessarily list files that are being tracked. However, many BitTorrent websites act as both a tracker and an index. Sites such as these publicize the tracker’s URL and allow users to upload torrents to the index with the tracker’s URL embedded in them, providing all the features necessary to initiate a download.

peer or leeches
A peer is another users computer on the Internet that you connect to download a file. Generally a peer does not have the complete file, otherwise it would be called a seed. Sometime peers are referred to as leeches, to distinguish them from users who have completed their download and have continue to leave the client running making them a seed. Leeching refers to users that have incomplete files.

seed or seeder
A users computer that has a complete copy of the file you want to download. Once your BitTorrent client completes downloading a file, it will remain open until you click the Finish button or close the BitTorrent file. This is known as being a seed or seeding. The user that keeps the client open with a completed download is called a seed or seeder.

swarm
The group of machines that are collectively connected for a particular file. For example, if you start a BitTorrent client and it tells you that you’re connected to 10 peers and 3 seeds, then the swarm consists of you and those 13 other people.

reseed
When there no seeds for a given file eventually all the peers trying to download will get stuck with an incomplete file, since no one in the swarm has the missing pieces to complete the file. If some nice user with a complete file (a seed) connects up to share with the swarm this is called reseeding.

downloading
Receiving the file FROM another user or peers’ computer.

uploading
Sending the file TO another user or peers’ computer.

Next Step in your BitTorrent Education

Now you have finished BitTorrent 101 beginners class. Hopefully you are now busy downloading files and feel you have a good idea of the basics of how this works. It is time to move on to the next stage and learn some tips on how to use BitTorrent more effectively.

TV Season Pass Automate BitTorrent
Set Up a TV Season Pass so you can download your favorite TV shows automatically as they become available. There are two applications that will allow you to set this up easily - Ted (Windows, Mac OS X, or Linux) or TVShows (Mac OS X only) both are free.

With either you subscribe to the TV shows you want to download and this helpful applications will find the files for you when they become available, no more searching. I have tested TVShows on my Mac. TV shows subscribed to automatically download when they are available, usually the day after they aired and most times in close to HD quality. The downloaded torrent file opens in your default BitTorrent client and automatically downloads with any intervention. Think of this as a BitTorrent replacement for a DVR.

Turn your computer into an Internet TV
Using a free cross-platform open source application called Miro (formally called Democracy Player) you can create a one-stop shop for handling video podcasts or BitTorrent. Miro is not as full featured as some BitTorrent clients like uTorrent or Transmission, but it does a nice job automatically downloading a season’s worth of TV. May be worth a look for many users.

Speeding up your downloads
No one is ever happy on how long it takes to do anything. I watch people who wait and complain in front of a microwave oven for food to heat! With BitTorrent, you can however take some simple steps to optimize your speeds.

1) First step is to try and pick a torrent that has lots of seeds, the more the better. Also the more seeds compared to peers the better. Usually 50 seeds and 50 peers is better than 500 seeds and 1000 peers.

2) Firewalls and NAT routers can slow your BitTorrent downloads. BitTorrent uses certain “ports” to communicate on, think of them as channels. If these ports of channels are not accessible speed of downloading with BitTorrent will suffer or may even stop.

NAT (network address translation) routers are present in most home networks and small business networks as they allow multiple computers to “share” one public IP address that is most likely dynamically assigned by your ISP. NAT routers usually have DHCP (dynamic host configuration protocol) running that distributes private IP addresses (10. or 192. addresses) to your computers connected to it acting like a natural firewall. Devices on the Internet usually only see your external public IP address and do not see the DHCP (or static IP) that is assigned to the computer sitting inside your network behind the NAT router.

NAT routers (Linksys, D-Link, Netgear, Apple, Actiontec, etc) work just fine with BitTorrent as they allow “outbound” connections, but other peers usually can not initiate connections to you. If connections can not initiated with other peers (especially if they are also firewalled) your download performance will suffer. Best way to fix this is set up Port Forwarding to allow TCP ports that BitTorrent uses to pass thru your NAT router to the computer you are running the BitTorrent client on.

BitTorrent (3.2 and later) uses TCP ports 6881-6999 (BitTorrent does not use UDP). Your BitTorrent client starts using the lowest port (6881) in this range and sequentially the higher ports until it finds one it can bind. Therefore, you only really need to open as many ports as simultaneous BitTorrent clients you would ever have open. It is usually sufficient to open just TCP ports 6881 thru 6889. Most trackers to which BitTorrent must connect usually are on port 6969, so the client must have outbound access on this port.

Setting up Port Forwarding on a NAT router is actually pretty easy. The step by step method does vary for each manufacturer however. Basically what you are doing is allowing remote computers to connect to a specific computer within your home network on a specific port or range of ports. Without Port Forwarding your NAT router would have usually rejected the request from the remote computer. Check the documentation that came with your router or the manufacturers website.

Speed Tip: BitTorrent uses ports 6881-6999 by default. Many ISP’s (Internet Service Providers) like to limit traffic on these ports to slow BitTorrent. Some BitTorrent clients allow you to change the range of ports to something else outsmarting your ISP.

Note: Having UPnP (Universal Plug and Play) enabled on your NAT router may allow Port Forwarding to be set more automatically. However, I usually advise that users disable this feature as it can create a big security hole. It alarms me that many routers built by the major manufaturers are defaulted on.

Firewalls, the software type, located on your computer can block or slow BitTorrent use. Windows Firewall has been long known to not play well with P2P. My suggestion is disable it and get yourself a third-party Firewall installed instead like Kerio or Zone Alarm.

Firewalls on OS X or Linux can of course also slow or block BitTorrent so configuring these may also be needed.

Hardware Firewalls may need to be setup to allow BitTorrent traffic. Do not expect a network administrator in a large company or organization to be friendly to this idea. If you plan on using BitTorrent on your company’s network, make sure you are not breaking the rules of using their network.

PortForward - Website to help setting up your router or Firewall.

3) Max TCP connections limited - Windows XP SP2 and Vista seems to limit simultaneous TCP connections. The TCP/IP stack is crippled in these versions of Windows as a so-called security enhancement. Seems Microsoft has determined that you only need 10 TCP connections (the previous limit was over 65,000) on Windows XP SP2, half that on Vista and only 2 on Vista Home Basic version.

Network intensive applications are greatly effected by this limitation. Applications like security network scanners, peer-to-peer (P2P) applications like BitTorrent or a combination of network applications that a power user may be using (VPN, FTP, P2P, RDP, SSH, and more) can be slowed or stopped in the name of Windows security. TorrentFreak has a fix for this possible problem.

4) Limiting your upload speed can improve download speed - If you limit your upload speed to approximately 80 percent of your maximum upload rate it may actually help your download speed. Check your upload speed on a good speed test like SpeakEasy (forget what your ISP says you get). Once you know your maximum upload speed, limit the maximum upload speed to about 80% in your BitTorrent client’s preferences. This may actually improve your download speed.

Another Speed Tip: Optimize your Internet connection with a free Windows utility called the TCP Optimizer. If you are running Macintosh OS X try Broadband Optimizer, Carrafix or Throttled.

5) ISP Throttling, Traffic Shaping and Slowing BitTorrent - Some ISPs (Internet Service Providers) are actively interfering with P2P including BitTorrent (cough, cough Comcast) in order to reduce their bandwidth requirements. This has been all over the news and is quite upsetting to the Net Neutrality crowd. These ISPs seem to just assume that the P2P traffic from their customers is only for sharing illegal copyrighted files. As I pointed out, BitTorrent (and other P2P) is used for many different types of file sharing. Mostly, the ISPs just want to save money. So this is a bit unfair, but on today’s net a fact of life.

BitTorrent clients like Azureus, BitComet, BitTornado, KTorrent, uTorrent, Transmission and rTorrent have introduced an encryption protocol (RC4 encryption) to prevent ISPs from identifying BitTorrent traffic. Encryption makes it hard for your ISP to detect that the traffic you are generating comes from BitTorrent. However, encryption uses a bit more CPU cycles and computer resources.

If you suspect that your ISP is throttling your BitTorrent traffic using encryption and changing the default ports 6881-6999 that BitTorrent uses is a start to outwit the “throttling machine.” See the Speed Tip above in the Firewalls and NAT routers section.

Some ISPs have learned to look for BitTorrent’s distinctive handshake. Luckily, uTorrent and Azureus/Vuze include a “Lazy Bitfield” feature to hide seeders from ISPs. When Lazy Bitfield is enabled, the handshake is changed possibly fooling your ISP into thinking the BitTorrent traffic going out is normal Internet traffic.

Tip: If ports are totally blocked check out Tunneling BitTorrent over SSH by Michael Whalen

Sandvine (the shaping tool many believe Comcast and other ISPs employ) won’t be fooled by obfuscating your traffic. Your only choice may be to switch to an ISP that doesn’t employ anti-BitTorrent traffic shaping. Maybe then your ex-ISP will get the message. Of course this is easier said then done for some users, as they is a serious lack of competition among ISPs with sometimes only one choice for broadband.

For a list of ISPs you might want to avoid, check out the list on the Azureus Wiki.

Is BitTorrent Safe For My Computer?
Like any other file you download from the Internet, you can not be sure if it contains a virus or malware. If you don’t trust the source of the file, then you should use extreme caution when opening it. Running a virus scan is usually a good idea. Keeping your machine’s anti-virus/spyware protection up to date especially if you use Windows) is very important. Regular backups of your data is essential.

BitTorrent does offer some protection as it makes sure you get what you asked for when you downloaded the torrent file. However, it can not guarantee that the original torrent file wasn’t malicious in the first place. This is why you will want to make sure your anti-virus software and Windows patches are up to date (something you should do anyway).

Can I be detected when using BitTorrent?
Short answer, absolutely. Your ISP, as with most everything you do on the Internet can tell what you are doing and what sites you have visited. As well as your network administrator in most large companies or organizations. As also Google or another search engine knows what you have searched for. Privacy on the Internet is a huge topic with many people concerned, as they should be.

Using BitTorrent Encryption Protocol is one way to stop your ISP from detecting that the traffic you are producing on their network is actually BitTorrent. But in no way should you believe this will prevent being detected at all.

There are some P2P-friendly services for hiding your online identity. Anonymizer.com, The Cloak, A4Proxy and Mute Anonymity. Most of these service charge a fee (a few are free) to providing anonymous proxy servers, software to hide IP addresses for surfing anonymously, web proxy technology, secure tunneling, and anonymous email. Even some of these products do not guarantee you would remain totally anonymous.

Most commercial VPN (virtual private network) services like HotSpotVPN also do not guarantee to hide your identity. In fact they reveal that they log all logins to the system and the FBI can subpoena those logs.

VPNTunnel (UK) is not free but looks like a possible fast and reliable service to protect users from the techniques shown in the video. I have not personally tried this. Some ISPs even throttle or inhibit these encrypted tunnels.

PeerGuardian 2 (Windows, Mac OS X, and Linux) is a popular IP blocking software which integrates support for multiple lists, list editing, automatic updates, and blocking all of IPv4 (TCP, UDP, ICMP, etc), helps keep anti-P2P organizations from tracking your downloads. Do Not get too excited, PeerGuardian 2 will not protect you completely it is only as good as the blacklist it uses.

Users seeking anonymity can achieve this by using a free proxy server from services like