MUD Protocols & Networking

Connection Model

Traditional MUDs operate over TCP/IP using the Telnet protocol (RFC 854/855). A player connects a client to a server’s IP address and port (commonly port 23 or 4000+). The connection lifecycle:

1. TCP connection established
2. Telnet option negotiation (capabilities exchange)
3. MUD-specific protocol negotiation (GMCP, MSDP, etc.)
4. Login/authentication
5. Gameplay (bidirectional text + out-of-band data)
6. Disconnect

Telnet Foundation

Basic Telnet (RFC 854)

• Text-based, bidirectional
• IAC (Interpret As Command, byte 255) introduces control sequences
• Options negotiated via WILL/WONT/DO/DONT sequences

Standard Telnet Options Used by MUDs

MUD-Specific Protocols

GMCP (Generic MUD Communication Protocol)

Telnet option code: 201

GMCP enables structured JSON data exchange between server and client without cluttering the text stream. It superseded ATCP.

Message format:

IAC SB GMCP <package.command> <JSON data> IAC SE

Negotiation:

• Server: IAC WILL GMCP
• Client accepts: IAC DO GMCP
• Client subscribes: Core.Supports.Set ["char 1", "room 1", "comm 1"]

Standard packages (as implemented by Aardwolf — the reference implementation):

char.base — Rarely-changing character info

{"name": "Lasher", "class": "Warrior", "subclass": "Soldier",
 "race": "Human", "clan": "Crusader", "pretitle": "",
 "tier": 9, "remorts": 7, "redos": 0, "level": 201, "pups": 500}

char.vitals — Health/resource tracking

{"hp": 100000, "mana": 90000, "moves": 41599}

char.stats — Training-affected values

{"str": 251, "int": 250, "wis": 249, "dex": 248, "con": 247, "luck": 246,
 "hr": 500, "dr": 500, "saves": -200}

char.maxstats — Maximum values

{"maxhp": 50099, "maxmana": 50029, "maxmoves": 30000,
 "maxstr": 300, "maxint": 300, "maxwis": 300, "maxdex": 300, "maxcon": 300, "maxluck": 300}

char.status — Experience and state

{"level": 210, "tnl": 1000, "hunger": 70, "thirst": 80,
 "align": 1000, "state": 3, "pos": "Standing", "enemy": "", "enemypct": ""}

State codes: 1=login, 2=MOTD, 3=active, 4=AFK, 5=note, 6=building, 7=pager, 8=combat, 9=sleeping, 11=resting, 12=running

char.worth — Currency and achievements

{"gold": 23128310661, "bank": 750000, "qp": 5052186, "tp": 1234,
 "trains": 5000, "pracs": 3000, "qpearned": 6000000}

room.info — Current location

{"num": 5922, "name": "At the Entrance to the Academy",
 "zone": "aylor", "terrain": "city",
 "details": "", "exits": {"e": 5920, "s": 5916, "w": 12611},
 "coord": {"id": 0, "x": 37, "y": 19, "cont": 1}}

Continent codes: 0=Mesolar, 1=Southern Ocean, 2=Gelidus, 3=Abend, 4=Alagh, 5=Uncharted Oceans, 6=Vidblain

comm.channels — All chat messages

{"chan": "gossip", "msg": "You gossip 'hello world'", "player": "Abelinc"}

Supported channels: answer, auction, barter, cant, chant, claninfo, clantalk, commune, curse, debate, ftalk, gametalk, gclan, gossip, grapevine, gratz, gsocial, gtell, helper, immtalk, inform, ltalk, market, music, newbie, nobletalk, pokerinfo, question, quote, racetalk, restores, rp, say, spouse, tech, telepathy, tell, tiertalk, wangrp, wardrums, yell

comm.quest — Quest lifecycle events

// Quest start
{"action": "start", "targ": "a goblin warrior", "room": "Dark Cave",
 "area": "Goblin Mines", "timer": 52}

// Quest complete
{"action": "comp", "qp": 16, "tierqp": 9, "pracs": 0, "trains": 0,
 "tp": 0, "gold": 4831, "completed": 111}

// Quest timeout
{"action": "timeout", "wait": 30}

comm.tick — Server pulse notification

{}

comm.repop — Area reset

{"zone": "aylor"}

group — Party information

{"groupname": "adventurers", "leader": "Lasher", "count": 2,
 "kills": 50, "exp": 10000,
 "members": [
   {"name": "Lasher", "hp": 50000, "mhp": 50000, "mana": 40000, "mmana": 40000,
    "moves": 30000, "mmoves": 30000, "align": 1000, "tnl": 500, "lvl": 201,
    "qt": 0, "qs": 0, "here": true}
 ]}

Quest status (qs): 0=can quest, 1=questing, 2=on cooldown, 3=mob/unable

MSDP (MUD Server Data Protocol)

Telnet option code: 69

Binary protocol for structured data exchange, developed 2009. More compact than GMCP but less human-readable.

Byte codes:

Format: IAC SB MSDP MSDP_VAR <variable> MSDP_VAL <value> IAC SE

Commands: LIST, REPORT (continuous updates), SEND (one-shot), RESET, UNREPORT

Standard reportable variables:

• General: account name, character name, server ID, server time
• Character: health, mana, experience, level, alignment, movement, money, status
• Combat: opponent name, health, level, strength
• Mapping: room vnum, coordinates, terrain, exits
• World: in-game time

MSSP (MUD Server Status Protocol)

Standardized server metadata for MUD directories and crawlers. Allows automated collection of accurate, real-time MUD information.

Required fields: NAME, PLAYERS (current count), UPTIME (Unix timestamp)

Categorization fields:

• FAMILY: AberMUD, CoffeeMUD, DikuMUD, Evennia, LPMud, MOO, TinyMUD, Custom, etc.
• GENRE: Fantasy, Sci-Fi, Horror, Modern, etc.
• GAMEPLAY: Hack and Slash, PvP, PvE, Roleplaying, Social, etc.
• STATUS: Alpha, Closed Beta, Open Beta, Live
• GAMESYSTEM: D&D, d20, Turn Based, Real Time, Custom, None

World metrics: AREAS, ROOMS, MOBILES, OBJECTS, CLASSES, LEVELS, RACES, SKILLS, HELPFILES

Protocol support flags: ANSI, UTF-8, VT100, XTERM 256 COLORS, XTERM TRUE COLORS

MXP (MUD eXtension Protocol)

HTML-like inline formatting for MUD output. Enables clickable links, styled text, images, and interactive elements.

Key tags:

• <A href="url"> — Open web link in browser
• <SEND href="command">text</SEND> — Clickable text that sends a command to the MUD
• <EXPIRE> — Remove previously displayed links (e.g., when changing rooms)
• <B>, <I>, <U>, <COLOR> — Text formatting
• Image maps with ISMAP attribute for clickable graphical elements

Use case: Room exits as clickable links, item names as clickable “look” commands, mob names as clickable “consider” commands.

MCCP (MUD Client Compression Protocol)

Zlib-based compression for MUD data streams. Two versions:

• MCCPv1: Telnet option 85 — compresses server→client only
• MCCPv2: Telnet option 86 — improved negotiation, widely supported

Reduces bandwidth 60-80% for text-heavy MUD output. Most modern clients support it.

ATCP (Achaea Telnet Client Protocol)

Predecessor to GMCP, developed by IRE (Iron Realms Entertainment) for Achaea and related MUDs. GMCP largely supersedes it but some MUDs still support both.

ANSI Color Codes

MUDs use ANSI escape sequences for colored text:

\033[<code>m

Standard 16 Colors

• Bold/bright: \033[1m (makes foreground bright)
• Reset: \033[0m
• 256-color: \033[38;5;<n>m (foreground), \033[48;5;<n>m (background)
• True color (24-bit): \033[38;2;<r>;<g>;<b>m

Modern Alternatives

WebSocket-Based MUDs

Modern MUDs increasingly support WebSocket connections alongside or instead of telnet:

• Browser-based clients with no installation
• Full HTML/CSS/JS for rich UI
• JSON messaging (similar to GMCP but native)
• Evennia includes a built-in HTML5 web client
• DikuMUD III (2020) uses HTML5 + WebSockets

Advantages of WebSocket approach

• Firewall-friendly (port 80/443)
• TLS encryption native
• Rich client capabilities (maps, sidebars, status bars)
• Mobile-friendly
• No special client software needed

Major MUD Clients

Sources

• Mudlet Supported Protocols
• TinTin++ GMCP
• TinTin++ MSDP
• TinTin++ MSSP
• Aardwolf GMCP Wiki
• MXP Specification
• GMCP Tutorial - Mudlet
• Gammon.com.au GMCP