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Tilehack

Nethack with Graphical Tiles - Online!

Online Nethack servers usually only offer Nethack via the text-only Telnet protocol. Only the classical text interface is available (right). But some players prefer the graphical interface that has been a standard part of offline Nethack since version 3.2 (released 1996).

One way to enable online tiled play is to guess a suitable tile to replace each on-screen character, based on its attributes, and substitute accordingly. This is the strategy used by David McCallum's program Ebonhack. It works for any Nethack server, but it isn't completely ideal. The text display does not contain as much information as a tiled display - some characters could represent more than one tile, and sometimes a page of text is mistaken for a map and vice versa. A better strategy (introduced by Justin Hiltscher for TelnetTiles) extends Nethack to generate hints about the correct tiles alongside the text characters.

Tilehack is a new approach to TelnetTiles, moving the client into Javascript running in a web browser. It is compatible with text mode and the popular dgamelaunch software. This makes it cross-platform and easy to use, and ensures that the tile set used by the players always matches the one used by the server. Naturally, a player can switch between tiled mode and text mode without starting a new game.

The Tilehack interface is similar to the graphical Nethack interface for MS-DOS: there is no mouse and menus are still text. However, the tiles appear exactly as they do within Nethack for Windows, Mac, MS-DOS and Linux (right).

Tilehack Servers

• This year, the /dev/null Nethack Tournament is providing tiled play as an option using Tilehack. It is currently available on four of the tournament servers, and I have so far ascended one Tourist in tiled mode.
• amuletofyendor.com also hosts a Tilehack server.

How it Works

1. Patch for Nethack

It takes effect only when $TERM = "tilehack". Tiles are drawn using VT100-style escape codes; there are additional escape codes to set the cursor colour according to the player's HP, as in Qt Nethack. These escape codes are chosen for compactness rather than compatibility with non-tiled terminals: unrecognised escape codes are supposed to be ignored, but some terminals try to interpret them anyway, so there is no way to produce output that is compatible both with Tilehack (or TelnetTiles) and with absolutely all non-tiled terminals.

2. Shellinabox-based Server

(There is also an earlier version based on shellinabox-2.10, and here is the diff for version 2.10 and the diff for SVN version 239.)

3. Tiles

The low 12 bits of number are the tile number, as used within Nethack's glyph2tile data structure. The 12th bit indicates if the tile represents a pet: if so, a small "heart" icon is added to the corner. For version 3.4.3, there are 1080 tiles, resulting in 2160 PNG images.

Setup

Then, the steps are (roughly) as follows:

1. Install the "tilehack" terminfo file on the Nethack server. Copy the "xterm" entry to a new entry named "tilehack". On Debian Linux, you can do this as follows: cp /usr/share/terminfo/x/xterm /usr/share/terminfo/t/tilehack. Unfortunately, this step is different on every OS, but without the "tilehack" terminfo file, you may see messages such as "Unknown terminal type: tilehack" and (if using dgamelaunch) you may not get any visible output!
2. Set up a web server such as Apache to serve the tile set under an URL such as http://example.com/nhtiles/ (substituting example.com for your web server's address).
3. Configure the web server to act as a reverse proxy whenever an URL such as /nethack/ is accessed. This reverse proxy should forward to "localhost" port 4200, the default port used by shellinabox. Here is an explanation of the procedure for Apache. No need to use SSL.
4. Run shellinaboxd with a command line such as:

   shellinaboxd -t -s '/:$user:$group:/:$command'

   In this command line, you must substitute $user and $group with the names of a valid user and group on your system. For testing, use your own username and group (the first two fields that are printed by the "id" command). For a real server, you should think about setting up a "chroot" environment and using dummy user accounts for extra security.
   
   $command should be "telnet -E $nethackserver", or an equivalent that respects your chroot environment. For regular telnet, -E is important: it disables the telnet escape sequences, which might otherwise allow a user to start a shell on your server.

Shellinabox is GPLv2-licensed software, written and copyright by Markus Gutschke. Tilehack would have been much more difficult if I had not been able to build upon this excellent piece of free software.

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		Copyright (C) Jack Whitham 1997-2011