MSSP  [protocol]
The Mud Server Status Protocol — how a game tells a crawler about itself.
Everything it reports is declared, not measured, and this site keeps the two
apart.
https://www.mudhalla.net/tintin/protocols/mssp/

Measured adoption
  318 of 886 listed games were observed offering it (35.9%)
  /games?protocol=MSSP

  The games not counted here are not games without the protocol. A game is
  counted when we observed its server offering the option in a handshake; the
  rest are servers that did not offer it to us and servers whose handshake we
  have not read, and we cannot tell you which.

  By codebase, of the games we identified
    FluffOS              28 of 28 offered it
    PennMUSH             28 of 34 offered it
    CoffeeMUD            18 of 32 offered it
    CircleMUD            15 of 47 offered it
    ROM                  12 of 55 offered it
    Evennia              11 of 11 offered it
    DikuMUD              6 of 35 offered it
    SMAUG                5 of 20 offered it
    MUCK                 4 of 24 offered it
    tbaMUD               4 of 5 offered it
    AresMUSH             3 of 18 offered it
    CobraMUSH            0 of 2 offered it
    RhostMUSH            0 of 40 offered it
    TinyMUSH             0 of 9 offered it

MSSP is telnet option 70. A crawler sends IAC DO MSSP; a server that supports it
replies with a table of name/value pairs describing itself — name, player count,
codebase, uptime, hostname, port, genre, and whatever else it cares to publish.

It is the closest thing this hobby has to a machine-readable directory entry,
and it is the reason several directories exist at all.

EVERYTHING IN AN MSSP REPORT IS AN ASSERTION

This is the point on which this site differs from every incumbent. An MSSP
report is the game telling you about itself. GMCP 1 in an MSSP table means
somebody typed 1 into a configuration file, possibly in 2011. It is not evidence
that the server offers GMCP, and the two disagree often enough to be
interesting.

So MSSP-derived facts are labelled declared here, and where we can measure the
same fact — a capability, by seeing whether the option is actually negotiated —
both are shown, side by side, with an age on each. A game whose MSSP has
declared GMCP for six years and has never once offered it in a handshake is a
fact worth knowing, and there is nowhere else you can find it.

The one field we deliberately do not credit at all is CREATED. It is a single
hand-typed line, and crediting it toward anything would make that thing
trivially gameable.

WHO ANSWERS IT

MSSP is the Diku and LP answer. In our own 38-codebase survey, 28 published a
player count through MSSP and seven through a login-screen WHO, and only two did
both — the two families are very nearly disjoint. AresMUSH, TinyMUX, MUCK,
RhostMUSH, CobraMUSH and TinyMUSH offer no MSSP whatsoever.

That is the empirical case for probing four layers rather than one: a crawler
built on MSSP alone cannot see most of the MUSH family, which is a large part of
the hobby and most of this site's intended audience.

ASK, DO NOT WAIT

A great many servers that fully support MSSP will never volunteer it — they
answer IAC DO MSSP and say nothing otherwise. A crawler that opens with IAC WILL
NAWS and waits therefore reports those games as publishing nothing, which is a
claim about the server made out of the crawler's own silence. We send IAC DO
MSSP on connect.

THE PLAINTEXT FORM

There is an older variant in which a client sends the literal line MSSP-REQUEST
at the login screen. We measured it: of twenty games tried, three answered — and
all three also answered telnet option 70, so it reached nothing the option did
not already reach. Eight servers read the request as a character name and said
so, spending one of the login attempts a stranger is allowed. We do not send it.

See also
  GMCP — /reference/protocols/gmcp
  DikuMUD — /reference/codebases/dikumud
  PennMUSH — /reference/codebases/pennmush