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.
+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 followed (depending on the
-command or response) by a message.
+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.
.B get \fITRACK\fR \fIPREF\fR
Gets a preference value. On success the second field of the response line will
have the value.
+.IP
+If the track or preference do not exist then the response code is 555.
.TP
.B get-global \fIKEY\fR
Get a global preference.
+.IP
+If the preference does not exist then the response code is 555.
.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 only terminate (and
-close the response body with a final dot) when a further command is readable on
-the control connection.
+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
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)
Pause the current track.
.TP
.B play \fITRACK\fR
-Add a track to the queue.
+Add a track to the queue. The response contains the queue ID of the track.
.TP
.B playing
Reports what track is playing.
.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
Unset a global preference.
.TP
.B user \fIUSER\fR \fIRESPONSE\fR
-Authenticate as \fIUSER\fR.
-.IP
-When a connection is made the server sends a \fB221\fR response before any
-command is received. As its first field this contains a challenge string
-encoded in hex.
-.IP
-The \fIRESPONSE\fR consists of the SHA-1 hash of the user's password
-concatenated with the challenge, encoded in hex.
+Authenticate as \fIUSER\fR. See
+.B AUTHENTICATION
+below.
.TP
.B version
Send back a response with the server version as the second field.
Text part is just commentary; an indefinite dot-stuffed body follows. (Used
for \fBlog\fR.)
.TP
-.B 4
-Text part is just commentary; an indefinite dot-stuffed body follows. (Used
-for \fBlog\fR.)
+.B 5
+Used with "normal" errors, for instance a preference not being found. The text
+part is commentary.
.TP
.B 9
The text part is just commentary (but would normally be a response for this
command) e.g. \fBplaying\fR.
.SH AUTHENTICATION
-The server starts by issuing a challenge line, with response code 231. This
-contains a random challenge encoded in hex.
+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 client should send back a \fBuser\fR command with username and a
-hex-encoded response. The response is the SHA-1 hash of the user's password
-and the challenge.
+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
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
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),
~mdw / disorder / blobdiff