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The magnet: URI scheme is a draft open standard defining a URI scheme for magnet links, which are mainly used to reference resources available for download via peer-to-peer networks. In the field of Computer networking, a URI scheme is the top level of the Uniform Resource Identifier (URI naming structure For other uses of the term see Peer-to-peer (disambiguation For peer-to-peer networks used for file sharing see File sharing Such a link typically identifies a file not by location or name, but by content, more precisely by the content's hash value. A hash function is any well-defined procedure or mathematical function for turning some kind of Data into a relatively small integer, that may

Since it refers to a file based on content or metadata, rather than by location, a magnet link can be considered a kind of URN (as opposed to the more common URLs). Metadata ( meta data, or sometimes metainformation) is "data about data" of any sort in any media A Uniform Resource Name ( URN) is a Uniform Resource Identifier (URI that uses the urn scheme, and does not imply availability of the identified Uniform Resource Locator is an URI which also specifies where the identified resource is available and the protocol for retrieving it Although it could be used for other applications, it is particularly useful in a peer-to-peer context, because it allows resources to be referenced without the need for a continuously available host.

The standard was developed in 2002, partly as a "vendor- and project-neutral generalization" of the ed2k: and freenet: URI schemes used by eDonkey2000 and Freenet, respectively, and attempts to follow official IETF URI standards as closely as possible. eDonkey2000 (nicknamed "ed2k" was a Peer-to-peer File sharing application developed by MetaMachine using the Multisource File Transfer Protocol Freenet is a decentralized Censorship -resistant Distributed data store originally designed by Ian Clarke. Applications supporting magnet links include Azureus, BearShare, DC++, gtk-gnutella, Kazaa, LimeWire, Morpheus, Shareaza, and TrustyFiles. DC++ is a free and open-source, Peer-to-peer file-sharing client that can be used to connect to the Direct Connect network gtk-gnutella is a Peer-to-peer file sharing application for Unix-like computer Operating systems which runs on the Gnutella network Kazaa Media Desktop (once capitalized as " KaZaA " but now usually written " Kazaa " is a Peer-to-peer File sharing application Morpheus was a File sharing and searching peer to peer client for Microsoft Windows, developed and distributed by the company StreamCast, that Shareaza is a Peer-to-peer file sharing client which supports the Gnutella, Gnutella2, EDonkey Network, BitTorrent, FTP TrustyFiles is a Closed source Microsoft Windows -based Peer-to-peer client which connects to the Gnutella, Gnutella2, FastTrack

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Use of content hashes

The most common use of magnet links is to link to a particular file based on a hash of its contents, producing a unique identifier for the file, similar to an ISBN or catalog number. A hash function is any well-defined procedure or mathematical function for turning some kind of Data into a relatively small integer, that may Unlike traditional identifiers, however, content-based signatures can be generated by anyone who already has the file, and so do not need a central authority to issue them. This makes them popular for use as "guaranteed" search terms within the file sharing community where anyone can distribute a magnet link to ensure that the resource retrieved by that link is the one intended, regardless of how it is retrieved. See Shared resource for the conventional meaning of file sharing File sharing refers to the providing and receiving of digital files over a (While it is technically possible that two files could have the same hash value, it is statistically very unlikely; see Cryptographic hash function). A cryptographic Hash function is a transformation that takes an input (or 'message' and returns a fixed-size string which is called the hash value (sometimes

Another advantage of magnet links is their open nature and platform independence: the same magnet link can be used to download a resource from one of any number of applications on almost any operating system. Because magnets are concise and plain-text, it is possible for users to simply copy-and-paste the links into emails or instant messages, a property not found in, for example, BitTorrent files. For a pejorative meaning see Cut and paste job In Human-computer interaction, cut and paste and copy and paste offer BitTorrent is a Peer-to-peer File sharing protocol used to distribute large amounts of Data.

Technical description

Magnet links consist of a series of one or more parameters, the order of which is not significant, formatted in the same way as the "query string" on the end of many HTTP URLs. Hypertext Transfer Protocol ( HTTP) is a Communications protocol for the transfer of information on the Internet. The most common parameter is "xt", meaning "exact topic", which is generally a URN formed from the content hash of a particular file, e. g.

Image:Magnet-icon.gif magnet:?xt=urn:sha1:YNCKHTQCWBTRNJIV4WNAE52SJUQCZO5C

referring to the SHA-1 hash of the file in question. Note that although this refers to a particular file, a search must still be carried out by the client application to determine where, if anywhere, it can obtain that file.

Other parameters defined by the draft standard are:

The standard also suggests that two parameters of the same type can be used by appending ". 1", ". 2", etc, e. g

Image:Magnet-icon.gif magnet:?xt. 1=urn:sha1:YNCKHTQCWBTRNJIV4WNAE52SJUQCZO5C&xt. 2=urn:sha1:TXGCZQTH26NL6OUQAJJPFALHG2LTGBC7


See also

External links

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