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[disorder] / doc / disorder_protocol.5.in

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.\" Copyright (C) 2004, 2005, 2006 Richard Kettlewell
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.TH disorder_protocol 5
.SH NAME
disorder_protocol \- DisOrder communication protocol
.SH DESCRIPTION
The DisOrder client and server communicate via the protocol described
in this man page.
.PP
The protocol is liable to change without notice.  You are recommended to check
the implementation before believing this document.
.SH "GENERAL SYNTAX"
Everything is encoded using UTF-8.  See
.B "CHARACTER ENCODING"
below for more detail on character encoding issues.
.PP
Commands and responses consist of a line perhaps followed (depending on the
command or response) by a body.
.PP
The line syntax is the same as described in \fBdisorder_config\fR(5) except
that comments are prohibited.
.PP
Bodies borrow their syntax from RFC821; they consist of zero or more ordinary
lines, with any initial full stop doubled up, and are terminated by a line
consisting of a full stop and a line feed.
.SH COMMANDS
Commands always have a command name as the first field of the line; responses
always have a 3-digit response code as the first field.  See below for more
details about this field.
.PP
All commands require the connection to have been already authenticated unless
stated otherwise.
.PP
Neither commands nor responses have a body unless stated otherwise.
.TP
.B allfiles \fIDIRECTORY\fR [\fIREGEXP\fR]
Lists all the files and directories in \fIDIRECTORY\fR in a response body.
If \fIREGEXP\fR is present only matching files and directories are returned.
.TP
.B become \fIUSER\fR
Instructs the server to treat the connection as if \fIUSER\fR had
authenticated it.  Only trusted users may issue this command.
.TP
.B dirs \fIDIRECTORY\fR [\fIREGEXP\fR]
Lists all the directories in \fIDIRECTORY\fR in a response body.
If \fIREGEXP\fR is present only matching directories are returned.
.TP
.B disable \fR[\fBnow\fR]
Disables further playing.  If the optional \fBnow\fR argument is present then
the current track is stopped.
.TP
.B enable
Re-enables further playing, and is the opposite of \fBdisable\fR.
.TP
.B enabled
Reports whether playing is enabled.  The second field of the response line will
be \fByes\fR or \fBno\fR.
.TP
.B exists \fITRACK\fR
Reports whether the named track exists.  The second field of the response line
will be \fByes\fR or \fBno\fR.
.TP
.B files \fIDIRECTORY\fR [\fIREGEXP\fR]
Lists all the files in \fIDIRECTORY\fR in a response body.
If \fIREGEXP\fR is present only matching files are returned.
.TP
.B get \fITRACK\fR \fIPREF\fR
Gets a preference value.  On success the second field of the response line will
have the value.
.TP
.B get-global \fIKEY\fR
Get a global preference.
.TP
.B length \fITRACK\fR
Gets the length of the track in seconds.  On success the second field of the
response line will have the value.
.TP
.B log
Sends event log messages in a response body.  The command will never terminate.
Any further data sent to the server will be discarded (explicitly; i.e. it will
not accumulate in a buffer somewhere).
.IP
See \fBEVENT LOG\fR below for more details.
.TP
.B move \fITRACK\fR \fIDELTA\fR
Move a track in the queue.  The track may be identified by ID (preferred) or
name (which might cause confusion if it's there twice).  \fIDELTA\fR should be
an negative or positive integer and indicates how many steps towards the head
of the queue the track should be moved.
.TP
.B moveafter \fITARGET\fR \fIID\fR ...
Move all the tracks in the \fIID\fR list after ID \fITARGET\fR.  If
\fITARGET\fR is the empty string then the listed tracks are put at the head of
the queue.  If \fITARGET\fR is listed in the ID list then the tracks are moved
to just after the first non-listed track before it, or to the head if there is
no such track.
.TP
.B new \fR[\fIMAX\fR]
Sends the most recently added \fIMAX\fR tracks in a response body.  If the
argument is ommitted, all recently added tracks are listed.
.TP
.B nop
Do nothing.  Used by
.BR disobedience (1)
as a keepalive measure.
.TP
.B part \fITRACK\fR \fICONTEXT\fI \fIPART\fR
Get a track name part.  Returns an empty string if a name part cannot be
constructed.
.IP
.I CONTEXT
is one of
.B sort
or
.B display
and
.I PART
is usually one of
.BR artist ,
.B album
or
.BR title .
.TP
.B pause
Pause the current track.
.TP
.B play \fITRACK\fR
Add a track to the queue.
.TP
.B playing
Reports what track is playing.
.IP
If the response is \fB252\fR then the rest of the response line consists of
track information (see below).
.IP
If the response is \fB259\fR then nothing is playing.
.TP
.B prefs \fBTRACK\fR
Sends back the preferences for \fITRACK\fR in a response body.
Each line of the response has the usual line syntax, the first field being the
name of the pref and the second the value.
.TP
.B queue
Sends back the current queue in a response body, one track to a line, the track
at the head of the queue (i.e. next to be be played) first.  See below for the
track information syntax.
.TP
.B random-disable
Disable random play (but don't stop the current track).
.TP
.B random-enable
Enable random play.
.TP
.B random-enabled
Reports whether random play is enabled.  The second field of the response line
will be \fByes\fR or \fBno\fR.
.TP
.B recent
Sends back the current recently-played list in a response body, one track to a
line, the track most recently played last.  See below for the track
information syntax.
.TP
.B reconfigure
Request that DisOrder reconfigure itself.  Only trusted users may issue this
command.
.TP
.B remove \fIID\fR
Remove the track identified by \fIID\fR.  If \fBrestrict remove\fR is enabled
in the server's configuration then only the user that submitted the track may
remove it.
.TP
.B rescan
Rescan all roots for new or obsolete tracks.
.TP
.B resolve \fITRACK\fR
Resolve a track name, i.e. if this is an alias then return the real track name.
.TP
.B resume
Resume the current track after a \fBpause\fR command.
.TP
.B rtp-address
Reports the RTP broadcast (or multicast) address, in the form \fIADDRESS
PORT\fR.
.TP
.B scratch \fR[\fIID\fR]
Remove the track identified by \fIID\fR, or the currently playing track if no
\fIID\fR is specified.  If \fBrestrict scratch\fR is enabled in the server's
configuration then only the user that submitted the track may scratch it.
.TP
.B search \fITERMS\fR
Search for tracks matching the search terms.  The results are put in a response
body, one to a line.
.IP
The search string is split in the usual way, with quoting supported, into a
list of terms.  Only tracks matching all terms are included in the results.
.IP
Any terms of the form \fBtag:\fITAG\fR limits the search to tracks with that
tag.
.IP
All other terms are interpreted as individual words which must be present in
the track name.
.IP
Spaces in terms don't currently make sense, but may one day be interpreted to
allow searching for phrases.
.TP
.B \fBset\fR \fITRACK\fR \fIPREF\fR \fIVALUE\fR
Set a preference.
.TP
.B set-global \fIKEY\fR \fIVALUE\fR
Set a global preference.
.TP
.B stats
Send server statistics in plain text in a response body.
.TP
.B \fBtags\fR
Send the list of currently known tags in a response body.
.TP
.B \fBunset\fR \fITRACK\fR \fIPREF\fR
Unset a preference.
.TP
.B \fBunset-global\fR \fIKEY\fR
Unset a global preference.
.TP
.B user \fIUSER\fR \fIRESPONSE\fR
Authenticate as \fIUSER\fR.  See
.B AUTHENTICATION
below.
.TP
.B version
Send back a response with the server version as the second field.
.TP
.B volume \fR[\fILEFT\fR [\fIRIGHT\fR]]
Get or set the volume.
.IP
With zero parameters just gets the volume and reports the left and right sides
as the 2nd and 3rd fields of the response.
.IP
With one parameter sets both sides to the same value.  With two parameters sets
each side independently.
.SH RESPONSES
Responses are three-digit codes.  The first digit distinguishes errors from
succesful responses:
.TP
.B 2
Operation succeeded.
.TP
.B 5
Operation failed.
.PP
The second digit breaks down the origin of the response:
.TP
.B 0
Generic responses not specific to the handling of the command.  Mostly this is
parse errors.
.TP
.B 3
Authentication responses.
.TP
.B 5
Responses specific to the handling of the command.
.PP
The third digit provides extra information about the response:
.TP
.B 0
Text part is just commentary.
.TP
.B 1
Text part is a constant result e.g. \fBversion\fR.
.TP
.B 2
Text part is a potentially variable result.
.TP
.B 3
Text part is just commentary; a dot-stuffed body follows.
.TP
.B 4
Text part is just commentary; an indefinite dot-stuffed body follows.  (Used
for \fBlog\fR.)
.TP
.B 9
The text part is just commentary (but would normally be a response for this
command) e.g. \fBplaying\fR.
.SH AUTHENTICATION
When a connection is made the server sends a \fB231\fR response before any
command is received.  This contains an algorithm name and a challenge encoded
in hex.
.PP
Currently the algorithm name is omitted if it is \fBsha1\fR (but this will
probably change in a future version).  The other options are \fBsha256\fR,
\fBsha384\fR and \fBsha512\fR.  \fBSHA1\fR etc work as synonyms.
.PP
The \fBuser\fR response consists of the selected hash of the user's password
concatenated with the challenge, encoded in hex.
.SH "TRACK INFORMATION"
Track information is encoded in a line (i.e. using the usual line syntax) as
pairs of fields.  The first is a name, the second a value.  The names have the
following meanings:
.TP 12
.B expected
The time the track is expected to be played at.
.TP
.B id
A string uniquely identifying this queue entry.
.TP
.B played
The time the track was played at.
.TP
.B scratched
The user that scratched the track.
.TP
.B state
The current track state.  Valid states are:
.RS
.TP 12
.B failed
The player failed (exited with nonzero status but wasn't scratched).
.TP
.B isscratch
The track is actually a scratch.
.TP
.B no_player
No player could be found for the track.
.TP
.B ok
The track was played without any problems.
.TP
.B scratched
The track was scratched.
.TP
.B started
The track is currently playing.
.TP
.B unplayed
In the queue, hasn't been played yet.
.TP
.B quitting
The track was terminated because the server is shutting down.
.RE
.TP
.B submitter
The user that submitted the track.
.TP
.B track
The filename of the track.
.TP
.B when
The time the track was added to the queue.
.TP
.B wstat
The wait status of the player in decimal.
.SH NOTES
Times are decimal integers using the server's \fBtime_t\fR.
.PP
For file listings, the regexp applies to the basename of the returned file, not
the whole filename, and letter case is ignored.  \fBpcrepattern\fR(3) describes
the regexp syntax.
.PP
Filenames are in UTF-8 even if the collection they come from uses some other
encoding - if you want to access the real file (in such cases as the filenames
actually correspond to a real file) you'll have to convert to whatever the
right encoding is.
.SH "EVENT LOG"
The event log consists of lines starting with a hexadecimal timestamp and a
keyword followed by (optionally) parameters.  The parameters are quoted in the
usual DisOrder way.  Currently the following keywords are used:
.TP
.B completed \fITRACK\fR
Completed playing \fITRACK\fR
.TP
.B failed \fITRACK\fR \fIERROR\fR
Completed playing \fITRACK\fR with an error status
.TP
.B moved \fIUSER\fR
User \fIUSER\fR moved some track(s).  Further details aren't included any
more.
.TP
.B playing \fITRACK\fR [\fIUSER\fR]
Started playing \fITRACK\fR.
.TP
.B queue \fIQUEUE-ENTRY\fR...
Added \fITRACK\fR to the queue.
.TP
.B recent_added \fIQUEUE-ENTRY\fR...
Added \fIID\fR to the recently played list.
.TP
.B recent_removed \fIID\fR
Removed \fIID\fR from the recently played list.
.TP
.B removed \fIID\fR [\fIUSER\fR]
Queue entry \fIID\fR was removed.  This is used both for explicit removal (when
\fIUSER\fR is present) and when playing a track (when it is absent).
.TP
.B rescanned
A rescan completed.
.TP
.B scratched \fITRACK\fR \fIUSER\fR
\fITRACK\fR was scratched by \fIUSER\fR.
.TP
.B state \fIKEYWORD\fR
Some state change occurred.  The current set of keywords is:
.RS
.TP
.B completed
The current track completed successfully.
.TP
.B disable_play
Playing was disabled.
.TP
.B disable_random
Random play was disabled.
.TP
.B enable_play
Playing was enabled.
.TP
.B enable_random
Random play was enabled.
.TP
.B failed
The current track failed.
.TP
.B pause
The current track was paused.
.TP
.B playing
A track started playing.
.TP
.B resume
The current track was resumed.
.TP
.B scratched
The current track was scratched.
.PP
To simplify client implementation, \fBstate\fR commands reflecting the current
state are sent at the start of the log.
.RE
.TP
.B volume \fILEFT\fR \fIRIGHT\fR
The volume changed.
.PP
.IR QUEUE-ENTRY ...
is as defined in
.B "TRACK INFORMATION"
above.
.SH "CHARACTER ENCODING"
All data sent by both server and client is encoded using UTF-8.  Moreover it
must be valid UTF-8, i.e. non-minimal sequences are not permitted, nor are
surrogates, nor are code points outside the Unicode code space.
.PP
There are no particular normalization requirements on either side of the
protocol.  The server currently converts internally to NFC, the client must
normalize the responses returned if it needs some normalized form for further
processing.
.PP
The various characters which divide up lines may not be followed by combining
characters.  For instance all of the following are prohibited:
.TP
.B o
LINE FEED followed by a combining character.  For example the sequence
LINE FEED, COMBINING GRAVE ACCENT is never permitted.
.TP
.B o
APOSTROPHE or QUOTATION MARK followed by a combining character when used to
delimit fields.  For instance a line starting APOSTROPHE, COMBINING CEDILLA
is prohibited.
.IP
Note that such sequences are not prohibited when the quote character cannot be
interpreted as a field delimiter.  For instance APOSTROPHE, REVERSE SOLIDUS,
APOSTROPHE, COMBINING CEDILLA, APOSTROPHE would be permitted.
.TP
.B o
REVERSE SOLIDUS (BACKSLASH) followed by a combining character in a quoted
string when it is the first character of an escape sequence.  For instance a
line starting APOSTROPHE, REVERSE SOLIDUS, COMBINING TILDE is prohibited.
.IP
As above such sequences are not prohibited when the character is not being used
to start an escape sequence.  For instance APOSTROPHE, REVERSE SOLIDUS,
REVERSE SOLIDS, COMBINING TILDER, APOSTROPHE is permitted.
.TP
.B o
Any of the field-splitting whitespace characters followed by a combining
character when not part of a quoted field.  For instance a line starting COLON,
SPACE, COMBINING CANDRABINDU is prohibited.
.IP
As above non-delimiter uses are fine.
.TP
.B o
The FULL STOP characters used to quote or delimit a body.
.PP
Furthermore none of these characters are permitted to appear in the context of
a canonical decomposition (i.e. they must still be present when converted to
NFC).  In practice however this is not an issue in Unicode 5.0.
.PP
These rules are consistent with the observation that the split() function is
essentially a naive ASCII parser.  The implication is not that these sequences
never actually appear in the protocol, merely that the server is not required
to honor them in any useful way nor be consistent between versions: in current
versions the result will be lines and fields that start with combining
characters and are not necessarily split where you expect, but future versions
may remove them, reject them or ignore some or all of the delimiters that have
following combining characters, and no notice will be given of any change.
.SH "SEE ALSO"
\fBdisorder\fR(1),
\fBtime\fR(2),
\fBdisorder\fR(3),
\fBpcrepattern\fR(3)
\fBdisorder_config\fR(5),
\fBdisorderd\fR(8),
\fButf8\fR(7)
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