eDonkey2000 network
(From Wikipedia, the free encyclopedia.)

eDonkey network (also called eDonkey2000 network or ed2k) is a file sharing network used primarily to exchange music, films and software. Like most file sharing networks, it is decentralized; files are not stored on a central server but are exchanged directly between users based on the peer to peer principle.

eDonkey client programs connect to the network to share files. eDonkey servers act as communication hubs for the clients and allow users to locate files within the network. Clients and servers are available for Windows, Macintosh, and Linux and other UNIX variants. Anyone can add a server to the network. Because of constant changes to the server network, clients update their server lists reguarly.

eDonkey uses a compound MD4 hash checksum to identify files which permits identification of identical files with different filenames. Another feature of eDonkey is that it shares file segments before the download completes; this speeds up file distribution throughout the network. To ease file searching, some websites list the checksums of sought-after files in the form of an ed2k link. Some of those websites also have lists of active servers for users to update.

The most widely used ed2k server software is Lugdunum, although MLDonkey provides an open source alternative.

In 2004, the eDonkey network overtook FastTrack to become the most widely used file sharing network on the Internet. While figures vary from hour to hour and day to day, it is thought to host on average approximately five million users sharing 500 million to a billion files via 100 to 200 servers. The network’s most popular server is Razorback2, which frequently hosts up to a million users.
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Clients

There are numerous clients for the eDonkey network, some of which are open source:
eMule: an open source Windows client; the most popular client, with 90% of network users. Ports of eMule to Unix platforms include xMule, lMule and aMule (which supports Win32 and Mac too).
EDonkey2000 (a client of MetaMachine): currently two versions are available, paid and free; however, the free version includes adware and spyware.
MLDonkey: a free software client that runs on many platforms and supports numerous other file-sharing protocols as well.
Shareaza: an open source multi-network client for Windows.
MediaVAMP (later changed to Pruna): a Korean-only client based on eMule.
lphant: a client that runs on the Microsoft .NET platform, and will hopefully soon work on emerging open-source clones of .NET like the Mono development platform, which will allow lphant to be used on alternative platforms such as GNU/Linux.