From b7b93bb67e9790d79e9d01a2dc03d4af361648a9 Mon Sep 17 00:00:00 2001 From: Rainer Hihn Date: Tue, 28 Aug 2018 18:08:22 +0200 Subject: [PATCH] First draft of the protocol as rst --- doc/protocol.rst | 1100 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 1100 insertions(+) create mode 100644 doc/protocol.rst diff --git a/doc/protocol.rst b/doc/protocol.rst new file mode 100644 index 000000000..54d97ef7c --- /dev/null +++ b/doc/protocol.rst @@ -0,0 +1,1100 @@ + + +================================ +The Music Player Daemon protocol +================================ + +General protocol syntax +####################### + +Protocol overview +================= + +The ``MPD`` command protocol exchanges +line-based text records between client and server over TCP. +Once the client is connected to the server, they conduct a +conversation until the client closes the connection. The +conversation flow is always initiated by the client. + +The client transmits a command sequence, terminated by the +newline character ``\n``. The server will +respond with one or more lines, the last of which will be a +completion code. + +When the client connects to the server, the server will answer +with the following line: + +CMDSYN: OK MPD version + +where ``version`` is a version identifier such as +0.12.2. This version identifier is the version of the protocol +spoken, not the real version of the daemon. (There is no way to +retrieve this real version identifier from the connection.) + +Requests +======== + +CMDSYN: COMMAND ARG + +If arguments contain spaces, they should be surrounded by double +quotation marks. + +Argument strings are separated from the command and any other +arguments by linear white-space (' ' or '\\t'). + +All data between the client and the server is encoded in +UTF-8. + +Responses +========= + +A command returns ``OK`` on completion or +``ACK some error`` on failure. These +denote the end of command execution. + +Failure responses +----------------- + +The nature of the error can be gleaned from the information +that follows the ``ACK``. +``ACK`` lines are of the form: + +CMDSYN: ACK [error@command_listNum] {current_command} message_text\n + +These responses are generated by a call to +``commandError``. They contain four separate +terms. Let's look at each of them: + +- ``error``: numeric value of one + of the ``ACK_ERROR`` constants defined + in `src/protocol/Ack.hxx`. + +- ``command_listNum``: + offset of the command that caused the error in a `Command List `. + An error will always cause a command list to terminate + at the command that causes the error. + +- ``current_command``: + name of the command, in a `Command List `, + that was executing when the error occurred. + +- ``message_text``: + some (hopefully) informative text that describes the + nature of the error. + +foo +~~~ + +An example might help. Consider the following sequence +sent from the client to the server. + +CMDSYN: command_list_begin volume 86 play 10240 status command_list_end + +The server responds with: + +``ACK \[50@1] {play} song doesn't exist: "10240"`` + +This tells us that the play command, which was the +second in the list (the first or only command is +numbered 0), failed with error 50. The number 50 +translates to ``ACK_ERROR_NO_EXIST``--the +song doesn't exist. This is reiterated by the message text +which also tells us which song doesn't exist. + +.. _command_lists: + +Command lists +============= + +To facilitate faster adding of files etc. you can pass a list +of commands all at once using a command list. The command +list begins with `command_list_begin` or +`command_list_ok_begin` and ends with +`command_list_end`. + +It does not execute any commands until the list has ended. +The return value is whatever the return for a list of commands +is. On success for all commands, +``OK`` is returned. If a command +fails, no more commands are executed and the appropriate +``ACK`` error is returned. If +`command_list_ok_begin` is used, +``list_OK`` is returned for each +successful command executed in the command list. + +Ranges +====== + +Some commands (e.g. `delete` `) +allow specifying a range in the form +*START:END* (the ``END`` +item is not included in the range, similar to ranges in the +Python programming language). If ``END`` is +omitted, then the maximum possible value is assumed. + +.. _filter_syntax: + +Filters +======= + +All commands which search for songs (e.g. `find` ` and +`searchadd` `) +share a common filter syntax: + +CMDSYN: find EXPRESSION + +``EXPRESSION`` is a string enclosed in +parantheses which can be one of: + +- ``(TAG == 'VALUE')``: match a tag value. + ``(TAG != 'VALUE')``: mismatch a tag value. + The special tag "*any*" checks all + tag values. + *albumartist* looks for + ``VALUE`` in ``AlbumArtist`` + and falls back to ``Artist`` tags if + ``AlbumArtist`` does not exist. + ``VALUE`` is what to find. The + `find` commands specify an exact value + and are case-sensitive; the `search` + commands specify a sub string and ignore case. + +- ``(file == 'VALUE')``: match the full song URI + (relative to the music directory). + +- ``(base 'VALUE')``: restrict the search to + songs in the given directory (relative to the music + directory). + +- ``(modified-since 'VALUE')``: compares the + file's time stamp with the given value (ISO 8601 or UNIX + time stamp). + +- ``(AudioFormat == 'SAMPLERATE:BITS:CHANNELS')``: + compares the audio format with the given value. + +- ``(AudioFormat =~ 'SAMPLERATE:BITS:CHANNELS')``: + matches the audio format with the given mask (i.e. one + or more attributes may be "*"). + +- ``(!EXPRESSION)``: negate an expression. + +- ``(EXPRESSION1 AND EXPRESSION2 ...)``: combine two or + more expressions with logical "and". + +Prior to MPD 0.21, the syntax looked like this: + +CMDSYN: find TYPE VALUE + +.. _tags: + +Tags +==== + +The following tags are supported by +``MPD``: + +There can be multiple values for some of these tags. For +example, ``MPD`` may return multiple +lines with a ``performer`` tag. A tag value is +a UTF-8 string. + +.. _other_metadata: + +Other Metadata +============== + +The response to `lsinfo` ` and +similar commands may contain `song +tags ` and other metadata, specifically: + +- ``duration``: the duration of the song in + seconds; may contain a fractional part. + +- ``time``: like ``duration``, + but as integer value. This is deprecated and is only here + for compatibility with older clients. Do not use. + +- ``Range``: if this is a queue item + referring only to a portion of the song file, then this + attribute contains the time range in the form + *START-END* or + *START-* (open ended); both + *START* and + *END* are time stamps within the song + in seconds (may contain a fractional part). Example: + "*60-120*" plays only the second + minute; "*180*" skips the first three + minutes. + +- ``Format``: the audio format of the song + (or an approximation to a format supported by MPD and the + decoder plugin being used). When playing this file, the + ``audio`` value in the `status` ` + response should be the same. + +- ``Last-Modified``: the time stamp of the + last modification of the underlying file in ISO 8601 + format. Example: + "*2008-09-28T20:04:57Z*" + +Recipes +####### + +Queuing +======= + +Often, users run ``MPD`` with ``random`` enabled, but want to +be able to insert songs "before" the rest of the playlist. +That is commonly called "queuing". + +``MPD`` implements this by allowing the client to specify a +"priority" for each song in the playlist (commands ``priod`` ` and +``priodid`` `). A +higher priority means that the song is going to be played +before the other songs. + +In "random" mode, ``MPD`` maintains an +internal randomized sequence of songs. In this sequence, +songs with a higher priority come first, and all songs with +the same priority are shuffled (by default, all songs are +shuffled, because all have the same priority "0"). When you +increase the priority of a song, it is moved to the front of +the sequence according to its new priority, but always after +the current one. A song that has been played already (it's +"before" the current song in that sequence) will only be +scheduled for repeated playback if its priority has become +bigger than the priority of the current song. Decreasing the +priority of a song will move it farther to the end of the +sequence. Changing the priority of the current song has no +effect on the sequence. During playback, a song's priority is +reset to zero. + +Command reference +################# + +.. note:: For manipulating playlists and playing, there are two sets of + commands. One set uses the song id of a song in the playlist, + while another set uses the playlist position of the song. The + commands using song ids should be used instead of the commands + that manipulate and control playback based on playlist + position. Using song ids is a safer method when multiple + clients are interacting with ``MPD``. + +Querying ``MPD``'s status +================================ + +CMDSYN: clearerror + Clears the current error message in status (this is also + accomplished by any command that starts playback). + +CMDSYN: currentsong + Displays the song info of the current song (same song that + is identified in status). + +CMDSYN: idle SUBSYSTEMS + Introduced with + ``MPD`` 0.14 + Waits until there is a noteworthy change in one or more + of ``MPD``'s subsystems. As soon + as there is one, it lists all changed systems in a line + in the format ``changed: + SUBSYSTEM``, where SUBSYSTEM is one of the + following: + - ``database``: the song database has been modified after `update` `. + - ``update``: a database update has started or finished. If the database was modified during the update, the ``database`` event is also emitted. + - ``stored_playlist``: a stored playlist has been modified, renamed, created or deleted + - ``playlist``: the current playlist has been modified + - ``player``: the player has been started, stopped or seeked + - ``mixer``: the volume has been changed + - ``output``: an audio output has been added, removed or modified (e.g. renamed, enabled or disabled) + - ``options``: options like repeat, random, crossfade, replay gain + - ``partition``: a partition was added, removed or changed + - ``sticker``: the sticker database has been modified. + - ``subscription``: a client has subscribed or unsubscribed to a channel + - ``message``: a message was received on a channel this client is subscribed to; this event is only emitted when the queue is empty + Change events accumulate, even while the connection is + not in "idle" mode; no events gets lost while the client + is doing something else with the connection. If an + event had already occurred since the last call, the new + `idle` ` + command will return immediately. + While a client is waiting for `idle` + results, the server disables timeouts, allowing a client + to wait for events as long as mpd runs. The + `idle` command can be canceled by + sending the command `noidle` (no other + commands are allowed). ``MPD`` + will then leave `idle` mode and print + results immediately; might be empty at this time. + If the optional ``SUBSYSTEMS`` argument + is used, ``MPD`` will only send + notifications when something changed in one of the + specified subsytems. + +CMDSYN: status + Reports the current status of the player and the volume + level. + - ``volume``: ``0-100`` or ``-1`` if the volume cannot be determined + - ``repeat``: ``0`` or ``1`` + - ``random``: ``0`` or ``1`` + - ``single``: Introduced with ``MPD`` 0.15 (oneshot introduced with 0.20). ``0``, ``1``, or ``oneshot`` + - ``consume``: ``0`` or ``1`` + - ``playlist``: 31-bit unsigned integer, the playlist version number + - ``playlistlength``: integer, the length of the playlist + - ``state``: ``play``, ``stop, or ``pause`` + - ``song``: playlist song number of the current song stopped on or playing + - ``songid``: playlist songid of the current song stopped on or playing + - ``nextsong``: playlist song number of the next song to be played + - ``nextsongid``: playlist songid of the next song to be played + - ``time``: total time elapsed (of current playing/paused song) + - ``elapsed``: Introduced with ``MPD`` 0.16. Total time elapsed within the current song, but with higher resolution. + - ``duration``: Introduced with ``MPD`` 0.20. Duration of the current song in seconds. + - ``bitrate``: instantaneous bitrate in kbps + - ``xfade``: ``crossfade`` in seconds + - ``mixrampdb``: ``mixramp`` threshold in dB + - ``mixrampdelay``: ``mixrampdelay`` in seconds + - ``audio``: The format emitted by the decoder plugin during playback, format: ``*samplerate:bits:channels*``. Check the user manual for a detailed explanation. + - ``updating_db``: ``job id`` + - ``error``: if there is an error, returns message here + +CMDSYN: stats + Displays statistics. + - ``artists``: number of artists + - ``albums``: number of albums + - ``songs``: number of songs + - ``uptime``: daemon uptime in seconds + - ``db_playtime``: sum of all song times in the db + - ``db_update``: last db update in UNIX time + - ``playtime``: time length of music played + +Playback options +================ + +CMDSYN: consume STATE + Sets consume state to ``STATE``, + ``STATE`` should be 0 or 1. + When consume is activated, each song played is removed from playlist. + +CMDSYN: crossfade SECONDS + Sets crossfading between songs. + +CMDSYN: mixrampdb deciBels + Sets the threshold at which songs will be overlapped. Like crossfading but doesn't fade the track volume, just overlaps. The songs need to have MixRamp tags added by an external tool. 0dB is the normalized maximum volume so use negative values, I prefer -17dB. In the absence of mixramp tags crossfading will be used. See http://sourceforge.net/projects/mixramp + +CMDSYN: mixrampdelay SECONDS + Additional time subtracted from the overlap calculated by mixrampdb. A value of "nan" disables MixRamp overlapping and falls back to crossfading. + +CMDSYN: random STATE + Sets random state to ``STATE``, + ``STATE`` should be 0 or 1. + +CMDSYN: repeat STATE + Sets repeat state to ``STATE``, + ``STATE`` should be 0 or 1. + +CMDSYN: setvol VOL + Sets volume to ``VOL``, the range of + volume is 0-100. + +CMDSYN: single STATE + Sets single state to ``STATE``, + ``STATE`` should be 0 or 1. + When single is activated, playback is stopped after current song, or + song is repeated if the 'repeat' mode is enabled. + +CMDSYN: replay_gain_mode MODE + Sets the replay gain mode. One of + *off*, + *track*, + *album*, + *auto* + added in ``MPD`` 0.16 + . + Changing the mode during playback may take several + seconds, because the new settings does not affect the + buffered data. + This command triggers the + ``options`` idle event. + +CMDSYN: replay_gain_status + Prints replay gain options. Currently, only the + variable ``replay_gain_mode`` is + returned. + +CMDSYN: volume CHANGE + Changes volume by amount ``CHANGE``. + .. note:: ``volume`` is deprecated, use ``setvol`` instead. + +Controlling playback +==================== + +CMDSYN: next + Plays next song in the playlist. + +CMDSYN: pause PAUSE + Toggles pause/resumes playing, ``PAUSE`` is 0 or 1. + .. note:: The use of pause command w/o the PAUSE argument is deprecated. + +CMDSYN: play SONGPOS + Begins playing the playlist at song number + ``SONGPOS``. + +CMDSYN: playid SONGID + Begins playing the playlist at song + ``SONGID``. + +CMDSYN: previous + Plays previous song in the playlist. + +CMDSYN: seek SONGPOS TIME + Seeks to the position ``TIME`` (in + seconds; fractions allowed) of entry + ``SONGPOS`` in the playlist. + +CMDSYN: seekid SONGID TIME + Seeks to the position ``TIME`` (in + seconds; fractions allowed) of song + ``SONGID``. + +CMDSYN: seekcur TIME + Seeks to the position ``TIME`` (in + seconds; fractions allowed) within the current song. If + prefixed by '+' or '-', then the time is relative to the + current playing position. + +CMDSYN: stop + Stops playing. + +The current playlist +==================== + +CMDSYN: add URI + Adds the file ``URI`` to the playlist + (directories add recursively). ``URI`` + can also be a single file. + +CMDSYN: addid URI POSITION + Adds a song to the playlist (non-recursive) and returns the song id. ``URI`` is always a single file or URL. For example: + + :: + addid "foo.mp3" + Id: 999 + OK + +CMDSYN: clear + Clears the current playlist. + +CMDSYN: delete POS START:END + Deletes a song from the playlist. + +CMDSYN: deleteid SONGID + Deletes the song ``SONGID`` from the + playlist + +CMDSYN: move FROM START:END TO + Moves the song at ``FROM`` or range of songs + at ``START:END`` to ``TO`` + in the playlist. + Ranges are supported since ``MPD`` 0.15 + +CMDSYN: moveid FROM TO + Moves the song with ``FROM`` (songid) to + ``TO`` (playlist index) in the + playlist. If ``TO`` is negative, it + is relative to the current song in the playlist (if + there is one). + +CMDSYN: playlist + Displays the current playlist. + .. note:: Do not use this, instead use `playlistinfo` `. + +CMDSYN: playlistfind TAG NEEDLE + Finds songs in the current playlist with strict + matching. + +CMDSYN: playlistid SONGID + Displays a list of songs in the playlist. + ``SONGID`` is optional and specifies a + single song to display info for. + +CMDSYN: playlistinfo SONGPOS START:END + Displays a list of all songs in the playlist, or if the optional + argument is given, displays information only for the song + ``SONGPOS`` or the range of songs + ``START:END`` + +CMDSYN: playlistsearch TAG NEEDLE + Searches case-insensitively for partial matches in the + current playlist. + +CMDSYN: plchanges VERSION START:END + Displays changed songs currently in the playlist since + ``VERSION``. Start and end positions may + be given to limit the output to changes in the given + range. + To detect songs that were deleted at the end of the + playlist, use playlistlength returned by status command. + +CMDSYN: plchangesposid VERSION START:END + Displays changed songs currently in the playlist since + ``VERSION``. This function only + returns the position and the id of the changed song, not + the complete metadata. This is more bandwidth efficient. + To detect songs that were deleted at the end of the + playlist, use playlistlength returned by status command. + +CMDSYN: prio PRIORITY START:END + Set the priority of the specified songs. A higher + priority means that it will be played first when + "random" mode is enabled. + A priority is an integer between 0 and 255. The default + priority of new songs is 0. + +CMDSYN: prioid PRIORITY ID + Same as ``priod`` `, + but address the songs with their id. + +CMDSYN: rangeid ID START:END + Since ``MPD`` + 0.19 Specifies the portion of the + song that shall be played. ``START`` and + ``END`` are offsets in seconds + (fractional seconds allowed); both are optional. + Omitting both (i.e. sending just ":") means "remove the + range, play everything". A song that is currently + playing cannot be manipulated this way. + +CMDSYN: shuffle START:END + Shuffles the current playlist. + ``START:END`` is optional and specifies + a range of songs. + +CMDSYN: swap SONG1 SONG2 + Swaps the positions of ``SONG1`` and + ``SONG2``. + +CMDSYN: swapid SONG1 SONG2 + Swaps the positions of ``SONG1`` and + ``SONG2`` (both song ids). + +CMDSYN: addtagid SONGID TAG VALUE + Adds a tag to the specified song. Editing song tags is + only possible for remote songs. This change is + volatile: it may be overwritten by tags received from + the server, and the data is gone when the song gets + removed from the queue. + +CMDSYN: cleartagid SONGID TAG + Removes tags from the specified song. If + ``TAG`` is not specified, then all tag + values will be removed. Editing song tags is only + possible for remote songs. + +Stored playlists +================ + +Playlists are stored inside the configured playlist directory. +They are addressed with their file name (without the directory +and without the `.m3u` suffix). + +Some of the commands described in this section can be used to +run playlist plugins instead of the hard-coded simple +`m3u` parser. They can access playlists in +the music directory (relative path including the suffix) or +remote playlists (absolute URI with a supported scheme). + +CMDSYN: listplaylist NAME + Lists the songs in the playlist. Playlist plugins are + supported. + +CMDSYN: listplaylistinfo NAME + Lists the songs with metadata in the playlist. Playlist + plugins are supported. + +CMDSYN: listplaylists + Prints a list of the playlist directory. + After each playlist name the server sends its last + modification time as attribute "Last-Modified" in ISO + 8601 format. To avoid problems due to clock differences + between clients and the server, clients should not + compare this value with their local clock. + +CMDSYN: load NAME START:END + Loads the playlist into the current queue. Playlist + plugins are supported. A range may be specified to load + only a part of the playlist. + +CMDSYN: playlistadd NAME URI + Adds ``URI`` to the playlist + `NAME.m3u`. + `NAME.m3u` will be created if it does + not exist. + +CMDSYN: playlistclear NAME + Clears the playlist `NAME.m3u`. + +CMDSYN: playlistdelete NAME SONGPOS + Deletes ``SONGPOS`` from the + playlist `NAME.m3u`. + +CMDSYN: playlistmove NAME FROM TO + Moves the song at position ``FROM`` in + the playlist `NAME.m3u` to the + position ``TO``. + +CMDSYN: rename NAME NEW_NAME + Renames the playlist `NAME.m3u` to `NEW_NAME.m3u`. + +CMDSYN: rm NAME + Removes the playlist `NAME.m3u` from + the playlist directory. + +CMDSYN: save NAME + Saves the current playlist to + `NAME.m3u` in the playlist directory. + +The music database +================== + +CMDSYN: albumart URI OFFSET + Searches the directory the file ``URI`` + resides in and attempts to return a chunk of an album + art image file at offset ``OFFSET``. + Uses the filename "cover" with any of ".png, .jpg, + .tiff, .bmp". + Returns the file size and actual number + of bytes read at the requested offset, followed + by the chunk requested as raw bytes, then a + newline and the completion code. + Example: + albumart + size: 1024768 + binary: 8192 + <8192 bytes> + OK + +CMDSYN: count FILTER group GROUPTYPE + Count the number of songs and their total playtime in + the database matching ``FILTER`` (see + `Filters `). The + following prints the number of songs whose title matches + "Echoes": + count title Echoes + The *group* keyword may be used to + group the results by a tag. The first following example + prints per-artist counts while the next prints the + number of songs whose title matches "Echoes" grouped by + artist: + count group artist + count title Echoes group artist + +CMDSYN: find FILTER sort TYPE window START : END + Search the database for songs matching + ``FILTER`` (see `Filters `). + ``sort`` sorts the result by the + specified tag. The sort is descending if the tag is + prefixed with a minus ('-'). + Without ``sort``, the + order is undefined. Only the first tag value will be + used, if multiple of the same type exist. To sort by + "Artist", "Album" or "AlbumArtist", you should specify + "ArtistSort", "AlbumSort" or "AlbumArtistSort" instead. + These will automatically fall back to the former if + "\*Sort" doesn't exist. "AlbumArtist" falls back to just + "Artist". The type "Last-Modified" can sort by file + modification time. + ``window`` can be used to query only a + portion of the real response. The parameter is two + zero-based record numbers; a start number and an end + number. + +CMDSYN: findadd FILTER + Search the database for songs matching + ``FILTER`` (see `Filters `) and add them to + the queue. Parameters have the same meaning as for + `find` `. + +CMDSYN: list TYPE FILTER group GROUPTYPE + Lists unique tags values of the specified type. + ``TYPE`` can be any tag supported by + ``MPD`` or + *file*. + Additional arguments may specify a `filter `. + The *group* keyword may be used + (repeatedly) to group the results by one or more tags. + The following example lists all album names, + grouped by their respective (album) artist: + list album group albumartist + +CMDSYN: listall URI + Lists all songs and directories in + ``URI``. + Do not use this command. Do not manage a client-side + copy of ``MPD``'s database. That + is fragile and adds huge overhead. It will break with + large databases. Instead, query + ``MPD`` whenever you need + something. + +CMDSYN: listallinfo URI + Same as `listall` `, + except it also returns metadata info in the same format + as `lsinfo` ` + Do not use this command. Do not manage a client-side + copy of ``MPD``'s database. That + is fragile and adds huge overhead. It will break with + large databases. Instead, query + ``MPD`` whenever you need + something. + +CMDSYN: listfiles URI + Lists the contents of the directory + ``URI``, including files are not + recognized by ``MPD``. + ``URI`` can be a path relative to the + music directory or an URI understood by one of the + storage plugins. The response contains at least one + line for each directory entry with the prefix "file: " + or "directory: ", and may be followed by file attributes + such as "Last-Modified" and "size". + For example, "smb://SERVER" returns a list of all shares + on the given SMB/CIFS server; "nfs://servername/path" + obtains a directory listing from the NFS server. + +CMDSYN: lsinfo URI + Lists the contents of the directory + ``URI``. The response contains records + starting with ``file``, + ``directory`` or + ``playlist``, each followed by metadata + (`tags ` or `other metadata `). + When listing the root directory, this currently returns + the list of stored playlists. This behavior is + deprecated; use "listplaylists" instead. + This command may be used to list metadata of remote + files (e.g. URI beginning with "http://" or "smb://"). + Clients that are connected via UNIX domain socket may + use this command to read the tags of an arbitrary local + file (URI is an absolute path). + +CMDSYN: readcomments URI + Read "comments" (i.e. key-value pairs) from the file + specified by "URI". This "URI" can be a path relative + to the music directory or an absolute path. + This command may be used to list metadata of remote + files (e.g. URI beginning with "http://" or "smb://"). + The response consists of lines in the form "KEY: VALUE". + Comments with suspicious characters (e.g. newlines) are + ignored silently. + The meaning of these depends on the codec, and not all + decoder plugins support it. For example, on Ogg files, + this lists the Vorbis comments. + +CMDSYN: search FILTER sort TYPE window START : END + Search the database for songs matching + ``FILTER`` (see `Filters `). Parameters + have the same meaning as for `find` `, + except that search is not case sensitive. + +CMDSYN: searchadd FILTER + Search the database for songs matching + ``FILTER`` (see `Filters `) and add them to + the queue. + Parameters have the same meaning as for `search` `. + +CMDSYN: searchaddpl NAME FILTER + Search the database for songs matching + ``FILTER`` (see `Filters `) and add them to + the playlist named ``NAME``. + If a playlist by that name doesn't exist it is created. + Parameters have the same meaning as for `search` `. + +CMDSYN: update URI + Updates the music database: find new files, remove + deleted files, update modified files. + ``URI`` is a particular directory or + song/file to update. If you do not specify it, + everything is updated. + Prints "updating_db: JOBID" where + ``JOBID`` is a positive number + identifying the update job. You can read the current + job id in the `status` ` + response. + +CMDSYN: rescan URI + Same as `update` `, + but also rescans unmodified files. + +Mounts and neighbors +==================== + +A "storage" provides access to files in a directory tree. The +most basic storage plugin is the "local" storage plugin which +accesses the local file system, and there are plugins to +access NFS and SMB servers. + +Multiple storages can be "mounted" together, similar to the +`mount` command on many operating +systems, but without cooperation from the kernel. No +superuser privileges are necessary, beause this mapping exists +only inside the ``MPD`` process + +CMDSYN: mount PATH URI + Mount the specified remote storage URI at the given + path. Example: + mount foo nfs://192.168.1.4/export/mp3 + +CMDSYN: unmount PATH + Unmounts the specified path. Example: + unmount foo + +CMDSYN: listmounts + Queries a list of all mounts. By default, this contains + just the configured ``music_directory``. + Example: + listmounts + mount: + storage: /home/foo/music + mount: foo + storage: nfs://192.168.1.4/export/mp3 + OK + +CMDSYN: listneighbors + Queries a list of "neighbors" (e.g. accessible file + servers on the local net). Items on that list may be + used with the `mount` ` + command. Example: + listneighbors + neighbor: smb://FOO + name: FOO (Samba 4.1.11-Debian) + OK + +Stickers +======== + +"Stickers" are pieces of +information attached to existing +``MPD`` objects (e.g. song files, +directories, albums). Clients can create arbitrary name/value +pairs. ``MPD`` itself does not assume +any special meaning in them. + +The goal is to allow clients to share additional (possibly +dynamic) information about songs, which is neither stored on +the client (not available to other clients), nor stored in the +song files (``MPD`` has no write +access). + +Client developers should create a standard for common sticker +names, to ensure interoperability. + +Objects which may have stickers are addressed by their object +type ("song" for song objects) and their URI (the path within +the database for songs). + +CMDSYN: sticker get TYPE URI NAME + Reads a sticker value for the specified object. + +CMDSYN: sticker set TYPE URI NAME VALUE + Adds a sticker value to the specified object. If a + sticker item with that name already exists, it is + replaced. + +CMDSYN: sticker delete TYPE URI NAME + Deletes a sticker value from the specified object. If + you do not specify a sticker name, all sticker values + are deleted. + +CMDSYN: sticker list TYPE URI + Lists the stickers for the specified object. + +CMDSYN: sticker find TYPE URI NAME + Searches the sticker database for stickers with the + specified name, below the specified directory (URI). + For each matching song, it prints the URI and that one + sticker's value. + +CMDSYN: sticker find TYPE URI NAME = VALUE + Searches for stickers with the given value. + Other supported operators are: + "``<``", "``>``" + +Connection settings +=================== + +CMDSYN: close + Closes the connection to ``MPD``. + ``MPD`` will try to send the + remaining output buffer before it actually closes the + connection, but that cannot be guaranteed. This command + will not generate a response. + +CMDSYN: kill + Kills ``MPD``. + +CMDSYN: password PASSWORD + This is used for authentication with the server. + ``PASSWORD`` is simply the plaintext + password. + +CMDSYN: ping + Does nothing but return "OK". + +CMDSYN: tagtypes + Shows a list of available tag types. It is an + intersection of the ``metadata_to_use`` + setting and this client's tag mask. + About the tag mask: each client can decide to disable + any number of tag types, which will be omitted from + responses to this client. That is a good idea, because + it makes responses smaller. The following + ``tagtypes`` sub commands configure this + list. + +CMDSYN: tagtypes disable NAME + Remove one or more tags from the list of tag types the + client is interested in. These will be omitted from + responses to this client. + +CMDSYN: tagtypes enable NAME + Re-enable one or more tags from the list of tag types + for this client. These will no longer be hidden from + responses to this client. + +CMDSYN: tagtypes clear + Clear the list of tag types this client is interested + in. This means that ``MPD`` will + not send any tags to this client. + +CMDSYN: tagtypes all + Announce that this client is interested in all tag + types. This is the default setting for new clients. + +Partition commands +================== + +These commands allow a client to inspect and manage +"partitions". A partition is one frontend of a multi-player +MPD process: it has separate queue, player and outputs. A +client is assigned to one partition at a time. + +CMDSYN: partition NAME + Switch the client to a different partition. + +CMDSYN: listpartitions + Print a list of partitions. Each partition starts with + a ``partition`` keyword and the + partition's name, followed by information about the + partition. + +CMDSYN: newpartition NAME + Create a new partition. + +Audio output devices +==================== + +CMDSYN: disableoutput ID + Turns an output off. + +CMDSYN: enableoutput ID + Turns an output on. + +CMDSYN: toggleoutput ID + Turns an output on or off, depending on the current + state. + +CMDSYN: outputs + Shows information about all outputs. + + :: + + outputid: 0 + outputname: My ALSA Device + plugin: alsa + outputenabled: 0 + attribute: dop=0 + OK + + Return information: + - ``outputid``: ID of the output. May change between executions + - ``outputname``: Name of the output. It can be any. + - ``outputenabled``: Status of the output. 0 if disabled, 1 if enabled. + +CMDSYN: outputset ID NAME VALUE + Set a runtime attribute. These are specific to the + output plugin, and supported values are usually printed + in the `outputs` ` + response. + +Reflection +========== + +CMDSYN: config + Dumps configuration values that may be interesting for + the client. This command is only permitted to "local" + clients (connected via UNIX domain socket). + The following response attributes are available: + Name + Description + ``music_directory`` + The absolute path of the music directory. + +CMDSYN: commands + Shows which commands the current user has access to. + +CMDSYN: notcommands + Shows which commands the current user does not have + access to. + +CMDSYN: urlhandlers + Gets a list of available URL handlers. + +CMDSYN: decoders + Print a list of decoder plugins, followed by their + supported suffixes and MIME types. Example response: + plugin: mad + suffix: mp3 + suffix: mp2 + mime_type: audio/mpeg + plugin: mpcdec + suffix: mpc + +Client to client +================ + +Clients can communicate with each others over "channels". A +channel is created by a client subscribing to it. More than +one client can be subscribed to a channel at a time; all of +them will receive the messages which get sent to it. + +Each time a client subscribes or unsubscribes, the global idle +event ``subscription`` is generated. In +conjunction with the `channels` ` +command, this may be used to auto-detect clients providing +additional services. + +New messages are indicated by the ``message`` +idle event. + +CMDSYN: subscribe NAME + Subscribe to a channel. The channel is created if it + does not exist already. The name may consist of + alphanumeric ASCII characters plus underscore, dash, dot + and colon. + +CMDSYN: unsubscribe NAME + Unsubscribe from a channel. + +CMDSYN: channels + Obtain a list of all channels. The response is a list + of "channel:" lines. + +CMDSYN: readmessages + Reads messages for this client. The response is a list + of "channel:" and "message:" lines. + +CMDSYN: sendmessage CHANNEL TEXT + Send a message to the specified channel. + +