Sounds and GMCP Softcode

Sounds and music reach a MUD client over GMCP beside the game’s text, and softcode can send GMCP messages of its own. Supporting MUD Clients explains GMCP and the MUD kit built on these.

Sounds and music

sound(), music() and stopsound() already play in MXP and Pueblo clients and in the web portal. A client that lists Client.Media in Core.Supports, as Mudlet does, is sent a GMCP message for each, just before the line they ride in:

> @pemit/list [pmatch(Wren)] [pmatch(Tam)]=[sound(door.wav,80)]The door creaks open.
Wren << Client.Media.Play {"name":"door.wav","type":"sound","volume":80}
Wren << The door creaks open.
Tam  << The door creaks open.
> @pemit *Wren=[music(theme.ogg,50,-1)]Music starts.
Wren << Client.Media.Play {"name":"theme.ogg","type":"music","volume":50,"loops":-1,"continue":false,"key":"music"}
> @pemit *Wren=[sound(https://cdn.example.org/fx/bell.wav)]A bell rings.
Wren << Client.Media.Play {"name":"bell.wav","url":"https://cdn.example.org/fx/","type":"sound"}
> @pemit *Wren=[stopsound(music)]The music stops.
Wren << Client.Media.Stop {"type":"music"}
> @pemit *Wren=[stopsound()]Silence.
Wren << Client.Media.Stop {}

Tam’s client listed nothing, so it was sent the line and no sound.

Client.Media.Play:

Field	What
name	the file to play
url	for a full web address, the directory it is in; left out for a file name, which the client fetches from Client.Media.Default
type	sound, or music for music()
volume	0 to 100, when given
loops	how many times to play, when given; -1 plays until stopped
continue, key	music only: key is music, so a new piece replaces the one playing

Client.Media.Stop has type sound or music for stopsound(effects) or stopsound(music), and no fields for stopsound(), which stops everything.

sound(), music() and stopsound() need a wizard or the Send_OOB power.

media_base_url

When sound() names a file rather than a full address, the client needs to know where the game keeps its sounds. Set media_base_url:

> @config/set media_base_url=https://example.org/sounds
Option set.

Every client that agrees to GMCP is then sent Client.Media.Default as it connects, before the login screen, and again whenever the setting changes. A / is added when the address does not end in one:

<< Client.Media.Default {"url":"https://example.org/sounds/"}

Empty sends nothing, and the game’s sounds then need full addresses. An imported PennMUSH mush.cnf that names it sets it too.

Functions for GMCP softcode

The MUD kit is ordinary softcode, built on three functions. Use them to send packages of your own.

gmcpsupports()

gmcpsupports(<descriptor|player>[, <package>]) returns the list a client sent in Core.Supports, or, given a package, 1 when the client listed it or a module it belongs to and 0 otherwise. Names match without regard to case.

> think gmcpsupports(me)
Char 1 Char.Skills 1 Char.Items 1 Room 1 IRE.Rift 1 IRE.Composer 1 External.Discord 1 Client.Media 1
> think gmcpsupports(me, Room.Info)
1
> think gmcpsupports(me, Comm.Channel)
0

A client that listed nothing returns an empty list, and 0 for every package:

> think strlen(gmcpsupports(me))
0
> think gmcpsupports(me, Room.Info)
0

A player name reads that player’s least idle connection. Reading anyone else’s connections needs a wizard or the Send_OOB power.

oob() with supported

oob(<players>, <package>[, <message>[, supported]]) sends a GMCP message and returns how many connections took it. With the fourth argument supported, a telnet client is sent the message only when it listed the package or a module it belongs to, or listed nothing at all. Without it, every client that agreed to GMCP is sent it. A portal connection always is.

Wren’s stock Mudlet did not list Comm:

> think oob(me, Comm.Channel.Text, json(object, channel, json(string, test)), supported)
0
> think oob(me, Comm.Channel.Text, json(object, channel, json(string, test)))
<< Comm.Channel.Text {"channel":"test"}
1

The MUD kit sends with supported, except Client.GUI and Client.Map. Use it for your own packages too, rather than testing gmcpsupports() first. Sending to anyone but yourself needs a wizard or the Send_OOB power. A descriptor number sends to that one connection, even before anyone has logged in on it, which is how a SOCKET`GMCP handler answers what a client asked.

exitmap()

exitmap(<room>[, <viewer>]) returns the exits in a room as a JSON object, each exit’s name to the number of the room it leads to: the exits of Room.Info.

> think exitmap(here)
{"north":26}

Only the exits the viewer can see are listed, the ones look would show them. Each is named up to its first ;, so north;n is north; when two exits share a name, the first is kept. An exit to HOME leads to the viewer’s own home, a variable exit is -2, and an unlinked exit is -1. You may map a room you can examine or are standing in.