Magnet URI scheme: Difference between revisions

Revision as of 22:47, 8 November 2009

Languages:

e

The magnet: URI scheme is an standard defining an [URI scheme] for so called magnet links. These links are mainly used by P2P applications to refer to files (normally by their hash value) located into their respecitve networks. As of today, magnets are the second most used P2P link worldwide (after torrents). For more information about how to use them inside of Shareaza, see MagnetsMakeAndUse.

Supporting Clients and Networks

Magnet links are supported by lots of P2P applications, including for example the following:

aMule (eD2k)
DC++ (DC network)
FrostWire (gnutella)
gtk-gnutella (gnutella)
Kazaa (FastTrack)
Morpheus (gnutella, G2)
Phex (gnutella)
Shareaza (eD2k, gnutella, G2, BT)
Sharelin (G2)
uTorrent (BT)
Vuze (BT)

As can be easily seen, magnet links are not limited to one or to an other network, as eD2k links or gnutella links for example.

Referring to Files by their Hashes

Magnet links use mostly hash sums of files to refer to a specific file inside a P2P network. These hash sums are similar to an (almost) unike fingerprint of a file and can only hardly be spoofed. Once a compatible client gets the information contained in a magnet link, it starts searching the network using the provided hashes. This returns exactly the file the link refers to which is/can be downloaded afterwards.

An additionnal advantage of magnet links is their platform independence and plain text format: Almost on all operating systems exist applications that support these links which makes it possible to download the linked-to contents from almost everywhere. Also, it is possible to copy/paste these links into emails or instant messages, which makes it very easy to send them for example to friends or other people that might be interested. This gives these links an enormeous advantage compared to .torrent files because these files are much harder to manipulate with or transmit to others.

Technical Details

Magnet links are based on a series of parameters, which can be used in any combination and order including information about one or several files. These parameters (also called tokens) can specify almost everything, from hashes of one or several files to their names or fix sources. Each token starts with a question mark followed by a two letter token code and the value of the respectice token. The most common parameter is "xt" (meaning "exact topic") which contains generally a content hash of the respective file the link points to. It can be used several times.

An (incomplete) list of available tokens can be seen here:

"as" (acceptable source): a source to be queried after not being able to find and download the file in the P2P networks in a defined amount of time. Most applications however treat this token exactly the same as the "xs" token.
"dn" (display name): a filename for the file to download
"kt" (keyword topic): specifys search terms instead of a particular file
"mt" (manifest topic): a URI pointing to a "manifest", e.g. a list of further items (rarely used because mostly obsolete)
"xl" (exact length): the size in bytes of the file
"xs" (exact source): a fixed source for the file. This is usuable an HTTP link
"xt" (exact topic): contains one or several hash values of a file. Can be used several times (hashes must be from the same file)
Each application can add specific experimental parameters, which must begin "x." to identify their experimental caracter

An example for a magnet URI is the following (it points to the installer of v2.4):

magnet:?xt=urn:bitprint:XZBS763P4HBFYVEMU5OXQ44XK32OMLIN.HGX3CO3BVF5AG2G34MVO3OHQLRSUF4VJXQNLQ7A&xt=urn:ed2khash:aa52fb210465bddd679d6853b491ccce&xl=6745696&dn=Shareaza_2.4.0.0.exe&xs=http%3A//195.123.7.32%3A6344/uri-res/N2R%3Furn%3Asha1%3AXZBS763P4HBFYVEMU5OXQ44XK32OMLIN

External links

MAGNET-URI Project Web-site on SourceForge
Bitzi, a search engine / directory providing information about files according to their hash.
Freebase a website that uses magnet links to index freeware. its cache works like a tracker for magnet links making finding other sources for a file more easy.

@@ Line 19: / Line 19: @@
 As can be easily seen, magnet links are not limited to one or to an other network, as eD2k links or gnutella links for example.
 ==Referring to Files by their Hashes==
+Magnet links use mostly hash sums of files to refer to a specific file inside a [[P2P network]]. These [[hash]] sums are similar to an (almost) unike fingerprint of a file and can only hardly be spoofed. Once a compatible client gets the information contained in a magnet link, it starts searching the network using the provided hashes. This returns exactly the file the link refers to which is/can be downloaded afterwards.
+An additionnal advantage of magnet links is their platform independence and plain text format: Almost on all operating systems exist applications that support these links which makes it possible to download the linked-to contents from almost everywhere. Also, it is possible to copy/paste these links into emails or instant messages, which makes it very easy to send them for example to friends or other people that might be interested. This gives these links an enormeous advantage compared to .[[torrent]] files because these files are much harder to manipulate with or transmit to others.
 ==Technical Details==
+Magnet links are based on a series of parameters, which can be used in any combination and order including information about one or several files. These parameters (also called tokens) can specify almost everything, from hashes of one or several files to their names or fix sources. Each token starts with a question mark followed by a two letter token code and the value of the respectice token. The most common parameter is "xt" (meaning "exact topic") which contains generally a content hash of the respective file the link points to. It can be used several times.
+An (incomplete) list of available tokens can be seen here:
+* "as" ('''acceptable source'''): a source to be queried after not being able to find and download the file in the P2P networks in a defined amount of time. Most applications however treat this token exactly the same as the "xs" token.
+* "dn" ('''display name'''): a filename for the file to download
+* "kt" ('''keyword topic'''): specifys search terms instead of a particular file
+* "mt" ('''manifest topic'''): a URI pointing to a "manifest", e.g. a list of further items (rarely used because mostly obsolete)
+* "xl" ('''exact length'''): the size in bytes of the file
+* "xs" ('''exact source'''): a fixed source for the file. This is usuable an HTTP link
+* "xt" ('''exact topic'''): contains one or several hash values of a file. Can be used several times (hashes must be from the same file)
+* Each application can add specific experimental parameters, which must begin "x." to identify their experimental caracter
+An example for a magnet URI is the following (it points to the installer of v2.4):
+ magnet:?xt=urn:bitprint:XZBS763P4HBFYVEMU5OXQ44XK32OMLIN.HGX3CO3BVF5AG2G34MVO3OHQLRSUF4VJXQNLQ7A&xt=urn:ed2khash:aa52fb210465bddd679d6853b491ccce&xl=6745696&dn=Shareaza_2.4.0.0.exe&xs=http%3A//195.123.7.32%3A6344/uri-res/N2R%3Furn%3Asha1%3AXZBS763P4HBFYVEMU5OXQ44XK32OMLIN
 ==External links==
+* [http://magnet-uri.sourceforge.net/ MAGNET-URI Project Web-site] on SourceForge
+* [http://bitzi.com/ Bitzi], a search engine / directory providing information about files according to their hash.
+* [http://www.freebase.be/ Freebase] a website that uses magnet links to index freeware. its cache works like a tracker for magnet links making finding other sources for a file more easy.