TLS  [protocol]
Encrypted connections. Usually a separate port rather than a negotiated upgrade,
and the one capability on this site we verify by connecting rather than by
asking.

Measured adoption
  0 of 886 listed games were observed offering it (0.0%)
  /games?protocol=TLS

  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
    AresMUSH             0 of 18 offered it
    CircleMUD            0 of 47 offered it
    CobraMUSH            0 of 2 offered it
    CoffeeMUD            0 of 32 offered it
    DikuMUD              0 of 35 offered it
    Evennia              0 of 11 offered it
    FluffOS              0 of 28 offered it
    MUCK                 0 of 24 offered it
    PennMUSH             0 of 34 offered it
    RhostMUSH            0 of 40 offered it
    ROM                  0 of 55 offered it
    SMAUG                0 of 20 offered it
    tbaMUD               0 of 5 offered it
    TinyMUSH             0 of 9 offered it

Telnet is plaintext. Everything you send a MU* — including your password —
crosses the network readable by anything on the path, unless the game offers
TLS.

In this hobby TLS almost always means a second port that speaks TLS from the
first byte, not an in-band upgrade. A game with a plain port on 4201 and a TLS
port on 4202 is the common shape. There is a negotiated variant, and it is rare
enough that at least one client's documentation explicitly says it is not
supported.

WHY THE GAME PAGES MARK THIS SPECIALLY

TLS is the one capability on this site established by doing it: an endpoint is
marked TLS because we completed a TLS handshake against it. There is no asking
involved and no field to declare, which makes it the cleanest measurement in the
catalogue.

That is also why a game's TLS port and its plain port are listed as separate
endpoints rather than merged. They are different measurements of different
things.

PRACTICAL ADVICE

If a game you play offers a TLS port, use it. If it does not and you care, ask —
it is a small amount of work for an administrator, and the reason it is not
universal is mostly that nobody has asked rather than that anybody objects.

Check whether your client supports it before you rely on it. Several in the
clients [/reference] section do; at least one documents a workaround with an
external stunnel process instead, which works and is more setup than most people
will do.

See also
  How to connect — /reference/connecting
  CHARSET — /reference/protocols/charset
  Potato MUSHclient — /reference/clients/potato