kazuya
16.04.09, 18:05
What is BitTorrent?
BitTorrent (often abbreviated to 'BT') is a P2P protocol (a set of rules and description of how to do things) allowing you to download files quickly by allowing people downloading the file to upload (distribute) parts of it at the same time. BitTorrent is often used for distribution of very large files, very popular files and files available for free, as it is a lot cheaper, faster and more efficient to distribute files using BitTorrent than a regular download.
What does BitTorrent?
BitTorrent allows a virtually unlimited number of people to connect to one another and share the same file at the same time. It uses the other clients who are also downloading the file to effectively act as servers to one another, simultaneously uploading the parts of the file received to others requesting the file. Hence, when you click on a file to download, several connections will be made to receive “slices” of the file that combine to create the entire file. Meanwhile, as you are downloading these “slices” you are also uploading them to anyone else that needs the parts you are receiving. Once the entire file is received it is considered polite to keep your client connected to act as a seed. A seed refers to a source that has the entire file available.
http://img18.imageshack.us/img18/1742/torrentcompsmall.gif
What is BitTorrent client?
A program that downloads files using the BitTorrent protocol.You can find today many clients for use like:Azureus,uTorrent,Bitcomet....
How do I install the client?
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.
Why does it take so long to start a big download?
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.
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.
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.
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.
Some basic terms:
Torrent
Usually this refers to the small metadata file you receive from the web server (the one that ends in .torrent.) Metadata here means that the file contains information about the data you want to download, not the data itself. This is what is sent to your computer when you click on a download link on a website. You can also save the 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 on without having to find the link again.
In some uses, it can also refer to everything associated with a certain file available with BitTorrent. For example, someone might say “I downloaded that torrent” or “that server has a lot of good torrents”, meaning there are lots of good files available via BitTorrent on that server.
Peer
A peer is another computer on the internet that you connect to and transfer data. Generally a peer does not have the complete file, otherwise it would be called a seed. Some people also refer to peers as leeches, to distinguish them from those generous folks who have completed their download and continue to leave the client running and act as a seed.
Seed
A computer that has a complete copy of a certain torrent. Once your client finishes downloading, it will remain open until you click the Finish button (or otherwise close it.) This is known as being a seed or seeding. You can also start a BT client with a complete file, and once BT has checked the file it will connect and seed the file to others. Generally, it’s considered good manners to continue seeding a file after you have finished downloading, to help out others. Also, when a new torrent is posted to a tracker, someone must seed it in order for it to be available to others. Remember, the tracker doesn’t know anything of the actual contents of a file, so it’s important to follow through and seed a file if you upload the torrent to a tracker.
Leech
A leech is a term with two meanings. Usually it is used to refer a peer who has a negative effect on the swarm by having a very poor share ratio - in other words, downloading much more than they upload. Most leeches are users on asymmetric internet connections and do not leave their BitTorrent client open to seed the file after their download has completed. However, some leeches intentionally avoid uploading by using modified clients or excessively limiting their upload speed. However the often used second meaning of leech is synonymous with downloader (see above) - used simply to describe a peer - or any client that does not have 100% of the data. This other meaning is mainly caused by most BitTorrent tracker sites using term leech in this sense.
Reseed
When there are zero seeds for a given torrent (and not enough peers to have a distributed copy), then eventually all the peers will get stuck with an incomplete file, since no one in the swarm has the missing pieces. When this happens, someone with a complete file (a seed) must connect to the swarm so that those missing pieces can be transferred. This is called reseeding. Usually a request for a reseed comes with an implicit promise that the requester will leave his or her client open for some time period after finishing (to add longevity to the torrent) in return for the kind soul reseeding the file.
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.
Tracker
A server on the Internet that acts to coordinate the action of BitTorrent clients. When you open a torrent, your machine contacts the tracker and asks for a list of peers to contact. Periodically throughout the transfer, your machine will check in with the tracker, telling it how much you’ve downloaded and uploaded, how much you have left before finishing, and the state you’re in (starting, finished download, stopping.) If a tracker is down and you try to open a torrent, you will be unable to connect. If a tracker goes down during a torrent (i.e., you have already connected at some point and are already talking to peers), you will be able to continue transferring with those peers, but no new peers will be able to contact you. Often tracker errors are temporary, so the best thing to do is just wait and leave the client open to continue trying.
Share-Ratio
This is simply the ratio of your amount uploaded divided by your amount downloaded. The amounts used are for the current session only, not over the history of the file. If you achieve a share ratio of 1.0, that would mean you’ve uploaded as much as you’ve downloaded. The higher the number, the more you have contributed. If you see a share ratio of “o:o”, this means infinity, which will happen if you open a BT client with a complete file (i.e., you seed the file.) In this case you download nothing since you have the full file, and so anything you send will cause the ratio to reach infinity. Note: The share rating is just a number that is displayed for your convenience. It does not directly affect any aspect of the client at all. In general, out of courtesy to others you should strive to keep this ratio as high as possible, of course.
Distributed Copies
In some versions of the client, you will see the text “Connected to n seeds; also seeing n.nnn distributed copies.” A seed is a machine with the complete file. However, the swarm can collectively have a complete copy (or copies) of the file, and that is what this is telling you. Referring again to the “people at a table” analogy, consider the case where the book has 10 pages, and person A has pp.1-5 and B has pp.6-10. Collectively, A and B have a complete copy of the book, even though no one person has the whole thing. In other words, even if there are no seeds, as long as there is at least one distributed copy of the file everyone can eventually get a complete file. Meditate on this, the Zen of BitTorrent, grasshopper.
Choked
Describes a peer to whom the client refuses to send file pieces. A client chokes another client in several situations:
The second client is a seed, in which case it does not want any pieces (ie. it is completely uninterested)
The client is already uploading at its full capacity (it has reached the value of max_uploads)
Pieces
Bit Torrent protocol was designed to break the file into small pieces and download them from different users to increase the speed of download. So a piece is nothing but a part of a file.
Hash
A unique alphanumeric value which is assigned to a file
Handshake:
This is a procedure followed by two clients when they start a connection.
Host 1 wants a file and finds that host 2 has that file then
Host 1 ----------> I want yyy file ----------> Host 2
Host 1 <---------- Ok i will send <---------- Host 2
Host 1 ----------> ok send the file----------> Host 2
Announce
Same as "scrape", but a client also announces that it wants to join the swarm and that server should add it to the peers in that swarm.
Scrape
This is when a client sends a request to the tracking server for information about the statistics of the torrent, such as with whom to share the file and how well those other users are sharing.
Downloading
Receiving data FROM another computer.
Uploading
Sending data TO another computer.
P2P
Stands for "peer to peer" which is the technology used for file sharing among computer users over the internet.
Private Tracker
Only registered users of a tracker can use this facility.
Public Tracker
Any member of the public can use this tracker for downloading the files
BitTorrent (often abbreviated to 'BT') is a P2P protocol (a set of rules and description of how to do things) allowing you to download files quickly by allowing people downloading the file to upload (distribute) parts of it at the same time. BitTorrent is often used for distribution of very large files, very popular files and files available for free, as it is a lot cheaper, faster and more efficient to distribute files using BitTorrent than a regular download.
What does BitTorrent?
BitTorrent allows a virtually unlimited number of people to connect to one another and share the same file at the same time. It uses the other clients who are also downloading the file to effectively act as servers to one another, simultaneously uploading the parts of the file received to others requesting the file. Hence, when you click on a file to download, several connections will be made to receive “slices” of the file that combine to create the entire file. Meanwhile, as you are downloading these “slices” you are also uploading them to anyone else that needs the parts you are receiving. Once the entire file is received it is considered polite to keep your client connected to act as a seed. A seed refers to a source that has the entire file available.
http://img18.imageshack.us/img18/1742/torrentcompsmall.gif
What is BitTorrent client?
A program that downloads files using the BitTorrent protocol.You can find today many clients for use like:Azureus,uTorrent,Bitcomet....
How do I install the client?
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.
Why does it take so long to start a big download?
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.
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.
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.
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.
Some basic terms:
Torrent
Usually this refers to the small metadata file you receive from the web server (the one that ends in .torrent.) Metadata here means that the file contains information about the data you want to download, not the data itself. This is what is sent to your computer when you click on a download link on a website. You can also save the 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 on without having to find the link again.
In some uses, it can also refer to everything associated with a certain file available with BitTorrent. For example, someone might say “I downloaded that torrent” or “that server has a lot of good torrents”, meaning there are lots of good files available via BitTorrent on that server.
Peer
A peer is another computer on the internet that you connect to and transfer data. Generally a peer does not have the complete file, otherwise it would be called a seed. Some people also refer to peers as leeches, to distinguish them from those generous folks who have completed their download and continue to leave the client running and act as a seed.
Seed
A computer that has a complete copy of a certain torrent. Once your client finishes downloading, it will remain open until you click the Finish button (or otherwise close it.) This is known as being a seed or seeding. You can also start a BT client with a complete file, and once BT has checked the file it will connect and seed the file to others. Generally, it’s considered good manners to continue seeding a file after you have finished downloading, to help out others. Also, when a new torrent is posted to a tracker, someone must seed it in order for it to be available to others. Remember, the tracker doesn’t know anything of the actual contents of a file, so it’s important to follow through and seed a file if you upload the torrent to a tracker.
Leech
A leech is a term with two meanings. Usually it is used to refer a peer who has a negative effect on the swarm by having a very poor share ratio - in other words, downloading much more than they upload. Most leeches are users on asymmetric internet connections and do not leave their BitTorrent client open to seed the file after their download has completed. However, some leeches intentionally avoid uploading by using modified clients or excessively limiting their upload speed. However the often used second meaning of leech is synonymous with downloader (see above) - used simply to describe a peer - or any client that does not have 100% of the data. This other meaning is mainly caused by most BitTorrent tracker sites using term leech in this sense.
Reseed
When there are zero seeds for a given torrent (and not enough peers to have a distributed copy), then eventually all the peers will get stuck with an incomplete file, since no one in the swarm has the missing pieces. When this happens, someone with a complete file (a seed) must connect to the swarm so that those missing pieces can be transferred. This is called reseeding. Usually a request for a reseed comes with an implicit promise that the requester will leave his or her client open for some time period after finishing (to add longevity to the torrent) in return for the kind soul reseeding the file.
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.
Tracker
A server on the Internet that acts to coordinate the action of BitTorrent clients. When you open a torrent, your machine contacts the tracker and asks for a list of peers to contact. Periodically throughout the transfer, your machine will check in with the tracker, telling it how much you’ve downloaded and uploaded, how much you have left before finishing, and the state you’re in (starting, finished download, stopping.) If a tracker is down and you try to open a torrent, you will be unable to connect. If a tracker goes down during a torrent (i.e., you have already connected at some point and are already talking to peers), you will be able to continue transferring with those peers, but no new peers will be able to contact you. Often tracker errors are temporary, so the best thing to do is just wait and leave the client open to continue trying.
Share-Ratio
This is simply the ratio of your amount uploaded divided by your amount downloaded. The amounts used are for the current session only, not over the history of the file. If you achieve a share ratio of 1.0, that would mean you’ve uploaded as much as you’ve downloaded. The higher the number, the more you have contributed. If you see a share ratio of “o:o”, this means infinity, which will happen if you open a BT client with a complete file (i.e., you seed the file.) In this case you download nothing since you have the full file, and so anything you send will cause the ratio to reach infinity. Note: The share rating is just a number that is displayed for your convenience. It does not directly affect any aspect of the client at all. In general, out of courtesy to others you should strive to keep this ratio as high as possible, of course.
Distributed Copies
In some versions of the client, you will see the text “Connected to n seeds; also seeing n.nnn distributed copies.” A seed is a machine with the complete file. However, the swarm can collectively have a complete copy (or copies) of the file, and that is what this is telling you. Referring again to the “people at a table” analogy, consider the case where the book has 10 pages, and person A has pp.1-5 and B has pp.6-10. Collectively, A and B have a complete copy of the book, even though no one person has the whole thing. In other words, even if there are no seeds, as long as there is at least one distributed copy of the file everyone can eventually get a complete file. Meditate on this, the Zen of BitTorrent, grasshopper.
Choked
Describes a peer to whom the client refuses to send file pieces. A client chokes another client in several situations:
The second client is a seed, in which case it does not want any pieces (ie. it is completely uninterested)
The client is already uploading at its full capacity (it has reached the value of max_uploads)
Pieces
Bit Torrent protocol was designed to break the file into small pieces and download them from different users to increase the speed of download. So a piece is nothing but a part of a file.
Hash
A unique alphanumeric value which is assigned to a file
Handshake:
This is a procedure followed by two clients when they start a connection.
Host 1 wants a file and finds that host 2 has that file then
Host 1 ----------> I want yyy file ----------> Host 2
Host 1 <---------- Ok i will send <---------- Host 2
Host 1 ----------> ok send the file----------> Host 2
Announce
Same as "scrape", but a client also announces that it wants to join the swarm and that server should add it to the peers in that swarm.
Scrape
This is when a client sends a request to the tracking server for information about the statistics of the torrent, such as with whom to share the file and how well those other users are sharing.
Downloading
Receiving data FROM another computer.
Uploading
Sending data TO another computer.
P2P
Stands for "peer to peer" which is the technology used for file sharing among computer users over the internet.
Private Tracker
Only registered users of a tracker can use this facility.
Public Tracker
Any member of the public can use this tracker for downloading the files