MUDs (Multi-User Dungeons) are text-driven cooperative or competitive games that you can play either straight from your terminal using the Telnet protocol or through a separate application specially designed to play MUDs. The majority of MUDs are free to play. Here's how you can get started with them.
To find a MUD that appeals to you, visit a MUD-list such as The Mud Connector or Mud Magic. Both have reviews and top-rated and "game of the month" features to help you find a MUD to jump into. I recommend Mud Magic for beginners, as it is easier to navigate and provides clear, comprehensive lists of top-10 MUDs.
Each MUD uses a different codebase and therefore has a distinct feel, play, and to a certain extent look. If you don't like how one game plays, try another. Even if you're happy with your first experience, shop around to see what's available, because MUDs vary greatly. Nobody says you can't play more than one. One general rule: if you're looking for action, not role-playing, avoid games with anything with MUSH listed as the codebase.
When you have found a game you want to try, open a terminal window and type
telnet to get open Linux's built-in Telnet connector. To connect to a MUD, type
open hostname/portnumber using the information from the MUD-list.
Inside the MUD
Once you're inside a MUD, you generally have to start by creating a character by following onscreen instructions. You will then be dropped into the game's prompt with a few instructions. Read them, because every MUD plays differently because of owner modifications. You should also be able to read help files by typing
help, and see a list of other current players by typing
who. Most of the time, the who list clearly specifies who is a staff member; you can direct questions to staffers using global chat commands, the use of which is most likely referred to in the opening instructions.
To begin, imagine yourself standing on a map, with the ability to go north, south, east, or west. Generally, you just type the direction you want to go in to go there, at which point you should get a new room description and a list of players there. More advanced MUDs let you move within rooms as well, or offer entirely different methods of movement.
Beyond basic telnet
If you have found a MUD that you enjoy playing, you're very likely to also have realized the limitations of basic Telnet for playing games. Luckily, you can find a multitude of applications that are specifically made to improve your MUDding experience. Clients for Linux include:
The MudMagic MUD Client offers multiple command input, full-colour text, tabbed playing, and command history -- plenty of features and a decent, usable GUI. It also includes a handy connection wizard.Gnome-MUD (for GNOME -- available in Ubuntu repositories) has a mapping function and supports ANSI coloured text, multiple command sends, and Python scripting, but is burdened by a lackluster GUI.Kmuddy (for KDE) offers ANSI coloured text, split screen for output history, command history, and multiple connections within the same instance. It's feature-loaded and has the nicest GUI of the native clients listed here. It also includes a wizard for such tasks as connecting on startup and game management.Tintin++ is a little old-fashioned, and not good for beginners, but a lot of clients use the basics of TT++'s scripting language.Xpertmud (RPM only, available in Gentoo repositories) has a powerful scripting language based on Python, but its GUI is severely lacking. It offers no mapping functions or copy/pasting from the open MUD window.
Sadly, the native Linux clients are severely lacking compared to the commercial Windows-based client Cmud (formerly Zmud). It is neither free nor open source, but it has a good GUI, a versatile scripting language, mapping functions, and includes the MUD-list from the Mud Connector built right into it. It reportedly works under Wine, but if it does work on your system, you can try an older free version that still surpasses most of the available native clients.
Running your own MUD
If you're intrigued by MUDding and would like to either look at source code for one or run your own MUD, you can find tarballs at Game.org. Look into the history of MUDding and the codebases before you dive into this archive, as games are arranged in a heirarchy according to which parent codebase they were developed from. A nice organized codebase to consider at first is ROM, located at /Diku/Merc/Rom/. For a little check on what game developers can actually accomplish with MUDs, take a look at God Wars II, or at least look through its New Player's Guide -> Combat section, which is simply astonishing in its complexity. For instance, it can utilize commands to make different body parts do separate things during combat.
Most of the codebases are written in C, though some written in C++ and Java. A few MUDs offer codebases that you can set up with no modification, or even with graphical tools that allow you to set one up without being proficient in any language. Linux.org lists a few codebases (and clients) that can be easily compiled under Linux.
Now that you know how to get started, jump right into the world of MUDding.