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From Wikipedia, the free encyclopedia

Server emulator is a term that is used to refer to an internet server that mimics the behavior of another server that is usually more well known. This is implemented through cloning or reverse engineering of the original server. Other synonyms include server reimplementation, server engine recreation, or server-side emulation. The term is widely used to describe reimplementation of MMORPG game servers, typically clones of proprietary commercial software by a third party. Technically, a server emulator does not emulate by the traditional definition, which would permit software from one hardware platform to run on a different one; it is more similar to a terminal emulator.



With the rising popularity of commercial MMORPG games, came the desire from ardent players of these games to run their own servers beside the ones run by the game's creator(s). Since the original server software is not usually available, the behavior of the server has to be reverse-engineered. This can be done by analyzing the data stream with the original server, or by disassembling and analyzing the game client which is available.

Ultima Online was one of the first large MMORPGs. Due to its openness in implementation, server emulators arose very quickly, even during the beta stage of development. The destination to which the client connects was changeable by simply editing a text file. In beta stage the client-server data stream was not encrypted yet. The term server emulator became known through Ultima Online server reimplementation such as UOX, which was the pioneer. Many forks and reimplementations followed UOX, because its source code was released under the GNU General Public License relatively early. RunUO is today the most widely used UO-server emulator.

Game companies usually try to hinder emulator development by encrypting the data stream. However, since the client needs to understand the data, the "attacker" is always equipped with a deciphering machine. Therefore, the original game designer can only add layers of strenuousness to decipher and understand the data stream, he cannot hinder it with cryptographic tools.


The legality or illegality of server emulators is a recurrent argument. There are several branches that are of concern:

Piracy: The most common situation for illegality of server emulation. Some commercial MMORPGs charge the player on a subscription basis, usually monthly. The majority of emulated servers allow clients to connect and avoid paying subscription fees. In other cases, there is a one-off payment for a license to use the software. Its game client can be downloaded when not normally available for free, thus also causing loss of revenue for the companies who own their games in a similar motive to traditional software piracy. Even though this may not apply to some games, other issues may take effect.

Copyright and Reverse engineering: Another issue is a possible infringement of the game creators copyright. As the case of Lotus v. Borland demonstrates, recreating "methods of operation" is not a copyright infringement. Thus, emulating copyrighted material is not a breach. However, this demands that the complete emulator is a work of its own. Sometimes the original server software leaks out of the company that created the game, for example AEGIS (Ragnarok Online). Use or distribution of leaked code is widely held to be copyright infringement.[citation needed] Modified versions of such original server software are not considered to be server emulators. There are cases where a game creator has effectively shut down popular private game servers by threatening lawsuits due to obvious copyright violations, such as offering the client for download or offering downloads of modified files from the original game package, or perceived copyright violations, such as simply offering an "unlicensed" version of the game, which may or may not constitute actual infringement.

End User License Agreement and the Digital Millennium Copyright Act: Another legal issue is the EULA. Today, most commercial MMORPGs require the user to sign a clause not to create or use server emulators when installing the client they bought.[citation needed]

Commonly mistaken as server emulators

  • Original server software that is stolen, like AEGIS, is not a server emulator.
  • Reimplementations of standardized protocols or server behavior is not considered to be emulation.
  • The program VMware Server is sometimes mistakenly called a "server emulator", while it is more precisely a hardware emulator (the words server and hardware being interchangeable in some circumstances). In the context of game server emulation, it is not a server emulator.

List of popular MMORPG's with a server emulator

See also

External links



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