what is magnet link?

what's the function behind it?

"A magnet link is a unique link to a specific file, typically on a P2P file sharing network.

Magnet Links allow users to directly download files into a P2P file sharing application. Through the support of magnet links, users can follow links to find specific files quickly and accurately. In short, getting the file is as easy as following a link - the magnet points to a specific file and launches the P2P program, adding the file to the user’s download list.

Magnet Links are an extension of a greater group of URIs/URNs (not to be confused with ‘URL’) - whereas a URL will point to a specific website; a URI will point to the specific contents, or, location of a file.

Magnet Links - What are they for?

The main reason for the conception of magnet links is for increased authenticity (and less redundancy) of files being shared via P2P programs. For example, if you conduct a search for something specific in a filesharing program (such as DC++), you’ll notice “multiple sources” for some of the results. We don’t have to tell you that ‘multiple source’ files offer the best availability, in terms of transfer speeds and chances for a successful ‘working’ download. All of the sources use the same hash link (that points to the exact same file).

Types of Hash Links

Magnet links were developed for the purpose of standardizing the existing hash formats. There is no standard for hash links (URI-schemes) that has been universally accepted by all P2P networks/clients (at least, not for downloading) thus it would be virtually impossible for a network to offer support for each one, let alone a P2P program. The magnet link solves this by acting as an umbrella for many types of hashes. Users therefore only require a P2P program that supports “magnet links” in order to employ the functionality and compatibility of most hash formats.

Here are some common formats of hash links:

    * — SHA1 (and newer SHA variants)
    * — MD4/MD5
    * — TTH (Tiger Tree Hashes)
    * — BitPrint (a combination of both SHA1 and TTH)
    * — eD2k hashes
    * — BTIH (BitTorrent hashes - specific to Azureus)

Magnet links will typically support multiple hashes (URIs/URNs) in the same “link”. The Magnet URI starts with “magnet:?” as its prefix.

Anti-Tampering

When a file is created, a hash is generated that is specific to that exact file, and it alone (although there is a slight possibility that the same hash could point to two different files, but the odds are billions to one against it). If a file (in this case, a P2P release) is modified even in slightest way, the hash value for it changes completely.

Say, for example, the MPAA downloads a good known P2P movie release, and somehow modifies it so that it won’t play, or so that it’ll display an anti-piracy message. If they redistribute that file back into the P2P network, the hash value will now be totally unique, and the file will not appear in the “group” of good files for a particular release.

P2P Clients in support of Magnet Links

Magnet links are becoming the standard protocol for most “hash links” due to their versatility. Here are just some of the P2P programs that currently support them:

    * — DC++ (and other ‘Direct Connect’ projects)
    * — Shareaza v2.3.1 / ShareazaPlus 2.2.5
    * — Limewire
    * — BearShare 5.2.5
    * — Phex v3.2
    * — MLDonkey
    * — Azureus (BitTorrent hashes only)

Magnet Links vs P2P ‘Client’ Searching

Since magnet links are designed to provide a viable link to an authentic file, P2P users are better served by searching for the magnet link of a particular file, as opposed to conducting queries from within the P2P client. This is exactly what makes the eDonkey network so popular - eD2k hash links.

If you have the proper magnet link, you can pretty much be assured that you’ll get the proper desired file (and not some decoy or spoof), without having to download it first. And since magnet links are so highly accurate in what they point to, websites that host them have come under fire from anti-piracy organizations. Their efforts towards spoofing or flooding of the P2P networks with bad or bogus files is utterly useless to anyone who uses good links.

Troubleshooting - Magnet Links and Protocol Association

Q: I’m not sure if I have a magnet handler. When I click a magnet link, I get an error message in my browser. What gives?

A: The most probable case is that you don’t have a “magnet-compatible” client, or it isn’t set up correctly to handle magnet links. You can check the settings in the client under file => settings => Advance => Register with Windows to handle Magnet: URI links.

Here are the error messages you’ll likely encounter in your browser if no P2P programs are associated with magnet links:

— Firefox is looking for an external program that isn’t associated with magnet links, as evident of the Application: <Unknown> message. Wait a few seconds and try to click the “Launch application” button at the bottom. This may or may not launch a default P2P program that handles your magnet links.

P2P Magnet-handler conflicts:

Each P2P program that is capable of handling magnet links will attempt to be the default magnet handler. If you already have a client such as Shareaza installed, and then you install DC++, it will likely lead to a ‘permanent’ or undoable decision within the Windows registry. If you’ve made a mistake by letting one program handle them (but you now wish for another to do it), change the parameter in the last line:

[HKEY_CLASSES_ROOT\magnet\shell\open\command]
@=”\”C:\\Program Files\\shareaza\\shareaza.exe\” \”%1\”"

If you’d like DC++ to open magnet links, change the last line to:

@=”\”C:\\Program Files\DC++\magnet.exe\” \”%1\”"

DC++ will now be the new default handler.

NOTE: This assumes that the P2P program were installed to the default directory (at C:\Program Files\DC++). Again, the parameter can be changed to fit any P2P program that supports magnets - just change to the proper path , pointing it to the proper name / location of the executable P2P program.

NOTE: Uninstalling one of the P2P programs will not necessarily result in another one gaining the rights to being the new “default” magnet handler. This is certainly the case with RevConnect (a Direct Connect client) - after installation, it remains set as the default regardless of what P2P program you install afterwards. So a modification in the Windows registry is the only thing that fixes this. Additionally, there are other ways to alter these settings in the registry (if you’re feeling brave enough to do it yourself) but the above method is by far the simplest method of changing it."

short version:
It's a tool for you to search and download the exact file that you are looking for. As it is most accurate then any other search method used in the client.

// LG

Damn that was a lengthy answer

thanks alot!