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`pianod2` Line Protocol

Following in the traditions of FTP, SMTP, POP, and other UNIX services, pianod2 accepts single-line commands and returns responses in the form of:

nnn Descriptive Text Here

A command is a series of terms separated by spaces. Terms are either:

A bare word
A series of words surrounded by double quotes. The opening double quote must immediately precede the first word, the closing quote must immediately follow the last word. Quotes in other places are treated as part of the term. There is no literal mechanism.

For example:

rename "Classical, Choral" to "Classical, Artistic Moaning"

This holds for all commands except filter expressions. A filter expression is parsed independently and obeys different rules. A filter expression must not be quoted:

SONG LIST WHERE ARTIST=“Madonna” & ALBUM=~”Virgin”

The filter expression starts at “ARTIST”. See Filter Grammar for details.

Websockets

A line (either command or response) on line-oriented socket interface is equivalent to one Websocket packet. The commands and response strings are identical, except that newlines are not included.

Response format

pianod2 responses take two forms:

nnn Descriptive Text
nnn Title: Value

nnn is a numerical status that should be used when interfacing with with other software.

For status message, descriptive text provides an explanation and possibly details. It is not internationalized but is subject to change.
For data messages, titles are composed of exactly one word (or use CamelCase), which is followed by colon, space, and a value.

Unlike many network services, pianod2 may spontaneously generate messages in response to playback changes, track changes, music mix changes, etc. The 6 categories of messages are arranged to make separating the command-response messages from spontaneous messages.

See the code (response.h) for assigned field numbers. Below are details for special cases.

Status Messages

000–099: Status. These indicate status that is not command-related.
100–199: Data. These identify specific pieces of information sent by the server. These messages may occur spontaneously or as part of a data response to a command; see [Data Responses][].
200–299: Success messages. These occur in response to commands.
300–399: Error detail messages. Zero or more of these precede a 400-class message and provide additional details relating to that error.
400–499: Command error messages. These occur in response to a command.
500–599: Other server errors. These indicate problems that are not command-related. For example, a server being down.

In most cases, exactly one of either a 200- or a 400-group message will occur in response to a command; the exception to this is 203 Data responses. One or more 300-group messages may occur as a result of command, and always supplement or qualify a subsequent 400-group message.

Playback Status (001–009)

Messages 001–019 indicate playback status.

001 (playbackState: playing), 002 (paused) & 003 (stalled)

Playback is playing, paused, and stalled respectively. The formatting for the messages is:

001 Playing: now/length/remain
002 Paused: now/length/remain
003 Stalled: now/length/remain

For example:

001 Playing: 02:27/04:12/-01:45

Stalled indicates the player should be playing, but is not, typically because of a buffer underrun caused by network issues.

004 (event code: 4)

The playing track has ended. This represents an event as opposed to a state.

005 (playbackState: betweenTracks)

The player is between tracks but cuing a song.

006 (playbackState: idle)

There is nothing playing or paused and the player will not start anything new for any reason: the player is paused, queue mode is stopped, there are no playlists selected, the queue mode is requests-only but queue empty, etc.

Queue mode

Regarding the difference between player state and queue mode: the player state is the CD player, the queue mode is the DJ.

007 (queueMode: stopped): Stopped.
008 (queueMode: requests): Request-only mode.
009 (queueMode: random): Random play mode. If there are no requests, random selections will be played.

Selections

011 (selectedSource)

Selected source. This message indicates the source that will be used when processing requests on this connection. The response format is:

011 SelectedSource: id type name

For example:

011 SelectedSource: 1 manager Pianod
011 SelectedSource: 2 tonegenerator Pianod

012 (selectedPlaylist)

Selected playlist for this room, which may not coincide with the playing playlist: first, the playlist may have been changed since the song started playing; and second, the selected playlist may be a mix or everything playlist, which encapsulates other playlists. The data format is:

012 SelectedPlaylist: type name

where type is one of mix (a manually-selected playlist mix), auto (an autotuned playlist mix), everything (all playlists are mixing), or playlist (a single playlist). For example:

012 SelectedPlaylist: mix Foobar's QuickMix
012 SelectedPlaylist: playlist Jazz Fusion
012 SelectedPlaylist: everything Metamix Bibliotheque

Event Notifications

Event notifications simply alert that something happened or changed, but provide no additional detail. It is up the client to request data if appropriate.

021: Mix selections have changed.
022: The list of playlists has changed. Implies possible mix change. If a parameter is included, it is the ID of the playlist effected.
023: Playlist ratings have changed. Broadcast per-user.
024: Sources available have changed. Implies possible playlist change.
025: Song rating changed. Parameter is ID of song.
026: Queue changed. Indicates insertion, removal or reorder of the queue. Not sent when playback starts; queue advance in this case is implied by playback status message.

Unusual Data Fields

116 (songRating)

Track rating information. The rating line always includes the rating as an adjective, then a numeric value (0.5–5.0; 0 indicates unrated), then 0 or more seed indications. Some examples:

116 Rating: good 4.0 seed
116 Rating: unheard 0.0 artistseed albumseed
116 Rating: repugnant 0.5

Rating adjectives includes: Unrated, repugnant, awful, bad, poor, lackluster, neutral, okay, good, excellent and superb.

Seed indications include: seed, albumseed, artistseed. Instead of presence/nonpresence, JSON protocol uses a dictionary:

"songRating":{
  "rating":3.0,  // will be "null" for unrated.
  "ratingText":"neutral", // "unrated" for unrated.
  "artistSeed":false,
  "albumSeed":false,
  "seed":false
}

120 (playlistRating)

Playlist rating, which is per pianod2 user. Spontaneous 120s apply to the playing track’s playlist, not the selected playlist. Format and adjectives are similar to 116. Like 116, JSON uses a dictionary.

127 (actions)

Actions. Indicates actions that may be taken for a given item. In addition to source capability variances, queue items may differ from search results (song suggestions) and seed listings (song seeds). Values include: request (the item may be requested), rate (the item may be rated), seed, albumseed, artistseed. Seeds apply to playlist actions; when included for a song, they indicate that the song may be seeded on the playlist from which it originates.

JSON instead uses a dictionary.

Data responses (203, 204)

Data responses occur in response to requests for playlist lists, current song, song queue, song history, etc. Data fields use the same numbering in both the response and spontaneous contexts, however, it is guaranteed that spontaneous data messages (100–199) will not occur between the initial 203 and final 204 of a response, allowing responses to be separated from other messages.

No Data

A single 204 End of data response occurs.

HISTORY LIST
204 No data or end of data

Single field list

If data is available, then there is a single 203 Data, followed by 1 or more data items (100–199), and finally a 204 End of data.

SOURCE TYPES LIST
203 Data
123 Source: manager
123 Source: pandora
123 Source: tonegenerator
204 No data or end of data
PLAYLISTS LIST NAMES
203 Data request ok
115 Playlist: Hard Rock Strength Training Radio
115 Playlist: New Age Beats Radio
115 Playlist: Chillout Radio
115 Playlist: Disco
115 Playlist: Symphonic, Classical Period
115 Playlist: Jazz Fusion
204 No data or end of data

Multi field list

If data is available, then there are one or more 203 Data responses, each followed by the individual data items. Following the last data group, a 204 End of Data occurs.

QUEUE LIST
203 Data request ok
111 ArtistID: S479098
112 Album: Big 6
113 Artist: Blue Mitchell
114 Title: Sir John
115 Playlist: Jazz Fusion
203 Data request ok
111 ArtistID: S278345
112 Album: Look At All The Love We Found: A Tribute To Sublime
113 Artist: The Greyboy Allstars
114 Title: Doin' Time
115 Playlist: Jazz Fusion
203 Data request ok
111 ArtistID: S551643
112 Album: Tutu
113 Artist: Miles Davis
114 Title: Portia
115 Playlist: Jazz Fusion
204 No data or end of data

Note that fields in records may not be homogenous; queue items from multiple sources, for example, may have differing fields. Playlist seeds is another example, where depending each the seed’s type (artist vs. album vs. song) included fields will vary.

Devious Fish pianod Command-line Overview

pianod2 Line Protocol

Websockets

Response format

Status Messages

Playback Status (001–009)

Queue mode

Selections

Event Notifications

Unusual Data Fields

Data responses (203, 204)

No Data

Single field list

Multi field list

Devious Fish
pianod Command-line Overview

`pianod2` Line Protocol