NAME¶
Moosic_API - How to write your own Moosic client.
Introduction¶
"moosicd" is a program that implements the server portion of the
Moosic jukebox system. This server provides services for manipulating a queue
of songs to be played, as well as for controlling the playing of these songs.
A Moosic client sends requests to the server, and receives data in response to
these requests. The "moosic" command line utility is the canonical
Moosic client, and provides a way to control a Moosic server from an
interactive command shell or from a shell script. However, you might not be
satisfied by the interface that is provided by the "moosic" command,
so I have written this document to describe how to communicate with a Moosic
server in your own programs.
[This document was written by Daniel Pearson <daniel@nanoo.org>, and has
been placed into the public domain.]
Section 0: Instructions for Impatient Developers¶
- 1.
- Plan to write your program with Python and xmlrpclib.
xmlrpclib is included with Python 2.2 or later, but if you need to use an
earlier version of Python, xmlrpclib can be downloaded from
<http://www.pythonware.com/products/xmlrpc/>.
- 2.
- If you can't or don't want to write your program with
Python and xmlrpclib, you won't benefit from this section and will have to
read section 2 of this document.
- 3.
- Create a proxy which communicates with moosicd:
>>> import moosic.client.factory
>>> proxy = moosic.client.factory.LocalMoosicProxy()
- 4.
- Read section 3 for the documentation of all the methods
supported by the proxy object.
- 5.
- Use the proxy to get information from the server and to
send commands to it. For example:
>>> proxy.list()
[]
>>> proxy.is_queue_running()
True
>>> proxy.haltqueue()
True
>>> proxy.is_queue_running()
False
>>> proxy.append([xmlrpc.Binary(i) for i in
... ['/home/daniel/music/Weird_Al/Pretty_Fly_for_a_Rabbi.mp3',
... '/home/daniel/music/Fiona_Apple/When_The_Pawn/04-Love_Ridden.ogg',
... "/home/daniel/music/Zelda/Great_Fairy's_Fountain.mid"]])
True
>>> proxy.list()
[<xmlrpclib.Binary instance at 0x843cf3c>,
<xmlrpclib.Binary instance at 0x8440e94>,
<xmlrpclib.Binary instance at 0x8440ebc>]
>>> [i.data for i in proxy.list()]
['/home/daniel/music/Weird_Al/Pretty_Fly_for_a_Rabbi.mp3',
'/home/daniel/music/Fiona_Apple/When_The_Pawn/04-Love_Ridden.ogg',
"/home/daniel/music/Zelda/Great_Fairy's_Fountain.mid"]
>>> proxy.sort()
True
>>> [i.data for i in proxy.list()]
['/home/daniel/music/Fiona_Apple/When_The_Pawn/04-Love_Ridden.ogg',
'/home/daniel/music/Weird_Al/Pretty_Fly_for_a_Rabbi.mp3',
"/home/daniel/music/Zelda/Great_Fairy's_Fountain.mid"]
- 6.
- If you wish to communicate with a moosicd that is listening
for requests on an IP socket instead of a Unix domain socket, you should
use InetMoosicProxy instead of LocalMoosicProxy. Here's an example:
>>> import moosic.client.factory
>>> proxy = moosic.client.factory.InetMoosicProxy('example.com', 8080)
Section 1: The Moosic Server's Data Model¶
This section describes, in precise terms, the data objects that can be accessed
and manipulated by sending requests to the Moosic server.
- song queue
- This is the foremost data object maintained by the Moosic
server. It is an ordered sequence of strings that represents the queue of
songs that are waiting to be played. Each item in this list identifies a
song that will be played by the Moosic server. Usually, these items are
the names of files on disk that contain each song, but this does not have
to be the case. For instance, an HTTP URL might be used to name a song if
a program that can play songs from the Web is appropriately registered
with the Moosic server (see "player configuration" later in this
section).
- current song
- This is a string that identifies the song that is currently
being played by the Moosic server. If nothing is currently playing, then
this will be the empty string.
- queue running flag
- This is a boolean value that indicates whether the Moosic
server will start playing a new song as soon as the current song has
finished and the song queue is not empty.
- pause flag
- This is a boolean value that indicates whether the current
song is paused or not.
- loop mode flag
- This is a boolean value that sets "loop mode".
When loop mode is on, songs are returned to the end of the song queue when
they finish playing instead of being discarded.
- history
- This is a list of songs that the Moosic server has finished
playing. Note that songs named in this list may have finished playing
early at the request of a user (i.e. through use of the "next"
command). Each entry in this list is actually a 3-tuple of (song, start
time, finish time).
- maximum history size
- This is the maximum number of songs that will be stored in
the history list. Old entries are removed from the history to make room
for newer entries when this limit is reached.
- player configuration
- This is an ordered mapping that associates regular
expressions (text patterns) to programs. For each regular expression, the
associated program is expected to be able to play any queue items that
match that regular expression. Each program is a list in which the name of
the executable file that contains the program is the first element and the
program's arguments are the rest of the elements.
- last queue update
- This is the time at which the song queue was last modified.
It a floating-point number that represents time as the number of seconds
since the epoch.
- server version
- This is a string that describes the version of the program
that implements the Moosic server. It has no specific, well-defined
semantics.
- API version
- This is a pair of integers, one representing the
"major" version, and the other representing the
"minor" version. These numbers are meant to provide some useful
compatibility information to Moosic clients. As this API changes, these
numbers will change in the following ways. If the API has been changed in
a backward-compatible way (e.g. a new method was added or an existing
method was overloaded), then the minor version will increase and the major
version will remain unchanged. However, if the API has been changed in
such a way that existing code that uses the API might break (e.g. a method
was removed or its return value or parameter types were changed), then the
major version will increase and the minor version may be reset to any
value (although it will usually be reset zero).
Section 2: The Low-Level Details of Client-Server
Communication¶
The information in this section is generally only necessary to people who wish
to write a Moosic client in a programming language other than Python. If you
are using Python to write a Moosic client, then you can use the classes
LocalMoosicProxy and InetMoosicProxy from the moosic_factory.py module, and
blissfully ignore most of these gory details. However, Python programmers can
also benefit from reading this section, as it will deepen their understanding
of Moosic's inter-process communication model.
The first thing to know about writing your own Moosic client is that
communication between the client and server is done through a BSD-style
socket. Read the "socket" manual page (and related manual pages) on
a Unix system if you are unfamiliar with BSD sockets. The socket used by
Moosic belongs to the Unix-domain protocol family (PF_UNIX or PF_LOCAL) and
has a type of SOCK_STREAM. This means that a Moosic client can only
communicate with a Moosic server that is running on the same computer as the
client. This limitation is a very purposeful part of Moosic's design. It has
the advantage of vastly reducing the consequences of any security flaws that
Moosic might have.
If you really, really think that you need the client and the server to run on
separate hosts, then you can run moosicd with the -t option, which tells it to
listen on a TCP/IP socket instead of a Unix domain socket. I recommend
firewalling such a port very carefully.
Regardless of which kind of socket is used by the server, XML-RPC is used as the
data protocol for requests and responses. For an introduction to XML-RPC, see
the XML-RPC homepage <
http://www.xmlrpc.com/> and the XML-RPC HOWTO
http://xmlrpc-c.sourceforge.net/xmlrpc-howto/xmlrpc-howto.html
<
http://xmlrpc-c.sourceforge.net/xmlrpc-howto/xmlrpc-howto.html>. Python
users should note that if the XML-RPC HOWTO tells you that you need to install
a third-party library to use XML-RPC, it is assuming that you are using a
Python version earlier than 2.2. Since version 2.2, Python has included the
xmlrpclib module in its standard library.
In summary, all you need to do to talk to a Moosic server in your own program is
to send XML-RPC requests to the appropriate address. By default, the
appropriate address for contacting moosicd is the file named
"socket" in a directory named ".moosic" in the home
directory of the user that started moosicd (i.e.
"~/.moosic/socket"). If moosicd is started with the -c option, then
the directory that contains "socket" will be the argument provided
to the -c option instead of ~/.moosic. If moosicd is started with the -t
option, then clients will have to address it by using a (host, port) pair
instead of a filename.
Section 3: Valid Moosic Server Methods¶
moosicd's XML-RPC server implements the introspection API mentioned on
http://xmlrpc-c.sourceforge.net/xmlrpc-howto/xmlrpc-howto-api-introspection.html
<
http://xmlrpc-c.sourceforge.net/xmlrpc-howto/xmlrpc-howto-api-introspection.html>,
so the API presented by moosicd is essentially self-documenting. Thus, the
information in this section has been automatically generated by querying a
running Moosic server.
The Moosic API contains the following methods:
- array api_version ()
-
Returns the version number for the API that the server implements.
Arguments: None.
Return value: The version number, which is a 2-element array of
integers. The first element is the major version, and the second
element is the minor version.
- boolean append (array)
-
Adds items to the end of the queue.
Argument: An array of (base64-encoded) strings, representing the items to be
added.
* When adding local filenames to the queue, only absolute pathnames should
be used. Using relative pathnames would be foolish because the server
has no idea what the client's current working directory is.
Return value: Nothing meaningful.
- boolean clear ()
-
Removes all items from the queue.
Arguments: None.
Return value: Nothing meaningful.
- boolean crop (array)
-
Remove all queued items that do not fall within the given range.
Arguments: An array of integers that represents a range.
* If the range contains a single integer, it will represent all members
of the queue whose index is greater than or equal to the value of the
integer.
* If the range contains two integers, it will represent all members of
the queue whose index is greater than or equal to the value of the
first integer and less than the value of the second integer.
* If the range contains more than two integers, an error will occur.
Return value: Nothing meaningful.
- boolean crop_list (array)
-
Removes all items except for those referenced by a list of positions.
Arguments: An array of integers that represents a list of the positions of
the items to be kept.
Return value: Nothing meaningful.
- base64 current ()
-
Returns the name of the currently playing song.
Arguments: None.
Return value: The name of the currently playing song.
- double current_time ()
-
Returns the amount of time that the current song has been playing.
Arguments: None.
Return value: The number of seconds that the current song has been playing.
- boolean cut (array)
-
Remove all queued items that fall within the given range.
Arguments: An array of integers that represents a range.
* If the range contains a single integer, it will represent all members
of the queue whose index is greater than or equal to the value of the
integer.
* If the range contains two integers, it will represent all members of
the queue whose index is greater than or equal to the value of the
first integer and less than the value of the second integer.
* If the range contains more than two integers, an error will occur.
Return value: Nothing meaningful.
- boolean cut_list (array)
-
Removes the items referenced by a list of positions within the queue.
Arguments: An array of integers that represents a list of the positions of
the items to be removed.
Return value: Nothing meaningful.
- boolean die ()
-
Tells the server to terminate itself.
Arguments: None.
Return value: Nothing meaningful.
- boolean filter (base64)
- boolean filter (base64, array)
-
Removes all items that don't match the given regular expression.
Arguments: A regular expression that specifies which items to keep.
* Optionally, an array of integers may be given as a second argument.
This argument represents a range to which the filtering will be
limited.
* If the range contains a single integer, it will represent all members
of the queue whose index is greater than or equal to the value of the
integer.
* If the range contains two integers, it will represent all members of
the queue whose index is greater than or equal to the value of the
first integer and less than the value of the second integer.
* If the range contains more than two integers, an error will occur.
Return value: Nothing meaningful.
- int get_history_limit ()
-
Gets the limit on the size of the history list stored in memory.
Arguments: None.
Return value: The maximum number of history entries that the server will
remember.
- array getconfig ()
-
Returns a list of the server's filetype-player associations.
Arguments: None.
Return value: An array of pairs. The first element of each pair is a
(base64-encoded) string that represents a regular expression pattern,
and the second element is a (base64-encoded) string that represents the
system command that should be used to handle songs that match the
corresponding pattern.
- boolean halt_queue ()
-
Stops any new songs from being played. Use run_queue() to reverse this
state.
Arguments: None.
Return value: Nothing meaningful.
- boolean haltqueue ()
-
Stops any new songs from being played. Use run_queue() to reverse this
state.
Arguments: None.
Return value: Nothing meaningful.
- array history ()
- array history (int)
-
Returns a list of the items that were recently played.
Arguments: If a positive integer argument is given, then no more than that
number of entries will be returned. If a number is not specified, or if
zero is given, then the entire history is returned. The result is
undefined if a negative integer argument is given (but does not raise an
exception).
Return value: An array of triples, each representing a song that was played
along with the times that it started and finished playing.
* The first member of the pair is a (base64-encoded) string which
represents the song that was previously played.
* The second member of the pair is a floating point number which
represents the time that the song started playing in seconds since the
epoch.
* The third member of the pair is a floating point number which
represents the time that the song finished playing in seconds since the
epoch.
- struct indexed_list ()
- struct indexed_list (array)
-
Lists the song queue's contents. If a range is specified, only the
items that fall within that range are listed.
This differs from list() only in its return value, and is useful when you
want to know the starting position of your selected range within the song
queue (which can be different than the starting index of the specified range
if, for example, the starting index is a negative integer).
Arguments: Either none, or an array of integers that represents a range.
* If no range is given, the whole list is returned.
* If the range contains a single integer, it will represent all members
of the queue whose index is greater than or equal to the value of the
integer.
* If the range contains two integers, it will represent all members of
the queue whose index is greater than or equal to the value of the
first integer and less than the value of the second integer.
* If the range contains more than two integers, an error will occur.
Return value: A struct with two elements. This first is "list", an array of
(base64-encoded) strings, representing the selected range from the song
queue's contents. The second is "start", an integer index value that
represents the position of the first item of the returned list in the
song queue.
- boolean insert (array, int)
-
Inserts items at a given position in the queue.
Arguments: The first argument is an array of (base64-encoded) strings,
representing the items to be added.
* The second argument specifies the position in the queue where the items
will be inserted.
* When adding local filenames to the queue, only absolute pathnames should
be used. Using relative pathnames would be foolish because the server
has no idea what the client's current working directory is.
Return value: Nothing meaningful.
- boolean is_looping ()
-
Tells you whether loop mode is on or not.
If loop mode is on, songs are returned to the end of the song queue after
they finish playing. If loop mode is off, songs that have finished playing
are not returned to the queue.
Arguments: None.
Return value: True if loop mode is set, False if it is not.
- boolean is_paused ()
-
Tells you whether the current song is paused or not.
Arguments: None.
Return value: True if the current song is paused, otherwise False.
- boolean is_queue_running ()
-
Tells you whether the queue consumption (advancement) is activated.
Arguments: None.
Return value: True if new songs are going to be played from the queue after
the current song is finished, otherwise False.
- double last_queue_update ()
-
Returns the time at which the song queue was last modified.
This method is intended for use by GUI clients that don't want to waste time
downloading the entire contents of the song queue if it hasn't changed.
Arguments: None.
Return value: A floating-point number that represents time as the number of
seconds since the epoch.
- int length ()
-
Returns the number of items in the song queue.
Arguments: None.
Return value: The number of items in the song queue.
- array list ()
- array list (array)
-
Lists the song queue's contents. If a range is specified, only the
items that fall within that range are listed.
Arguments: Either none, or an array of integers that represents a range.
* If no range is given, the whole list is returned.
* If the range contains a single integer, it will represent all members
of the queue whose index is greater than or equal to the value of the
integer.
* If the range contains two integers, it will represent all members of
the queue whose index is greater than or equal to the value of the
first integer and less than the value of the second integer.
* If the range contains more than two integers, an error will occur.
Return value: An array of (base64-encoded) strings, representing the
selected range from the song queue's contents.
- boolean move (array, int)
-
Moves a range of items to a new position within the queue.
Arguments: The first argument is an array of integers that represents a
range of items to be moved.
* If the range contains a single integer, it will represent all members
of the queue whose index is greater than or equal to the value of the
integer.
* If the range contains two integers, it will represent all members of
the queue whose index is greater than or equal to the value of the
first integer and less than the value of the second integer.
* If the range contains more than two integers, an error will occur.
* The second argument, "destination", specifies the position in the queue
where the items will be moved.
Return value: Nothing meaningful.
- boolean move_list (array, int)
-
Moves the items referenced by a list of positions to a new position.
Arguments: The first argument is an array of integers that represents a
list of the positions of the items to be moved.
* The second argument, "destination", specifies the position in the queue
where the items will be moved.
Return value: Nothing meaningful.
- boolean next ()
- boolean next (int)
-
Stops the current song (if any), and jumps ahead to a song that is
currently in the queue. The skipped songs are recorded in the history as if
they had been played. When called without arguments, this behaves very
much like the skip() method, except that it will have an effect even if
nothing is currently playing.
Arguments: A single integer that tells how far forward into the song queue
to advance. A value of 1 will cause the first song in the queue to play,
2 will cause the second song in the queue to play, and so on. If no
argument is given, a value of 1 is assumed.
Return value: Nothing meaningful.
- boolean no_op ()
-
Does nothing, successfully.
Arguments: None.
Return value: Nothing meaningful.
- boolean pause ()
-
Pauses the currently playing song.
Arguments: None.
Return value: Nothing meaningful.
- boolean prepend (array)
-
Adds items to the beginning of the queue.
Argument: An array of (base64-encoded) strings, representing the items to be
added.
* When adding local filenames to the queue, only absolute pathnames should
be used. Using relative pathnames would be foolish because the server
has no idea what the client's current working directory is.
Return value: Nothing meaningful.
- boolean previous ()
- boolean previous (int)
-
Stops the current song (if any), removes the most recently played song
from the history, and puts these songs at the head of the queue. When loop
mode is on, the songs at the tail of the song queue are used instead of the
most recently played songs in the history.
Arguments: A single integer that tells how far back in the history list to
retreat. A value of 1 will cause the most recent song to play, 2 will
cause the second most recent song to play, and so on. If no argument is
given, a value of 1 is assumed.
Return value: Nothing meaningful.
- boolean putback ()
-
Places the currently playing song at the beginning of the queue.
Arguments: None.
Return value: Nothing meaningful.
- int queue_length ()
-
Returns the number of items in the song queue.
Arguments: None.
Return value: The number of items in the song queue.
- boolean reconfigure ()
-
Tells the server to reread its player configuration file.
Arguments: None.
Return value: Nothing meaningful.
- boolean remove (base64)
- boolean remove (base64, array)
-
Removes all items that match the given regular expression.
Arguments: A regular expression that specifies which items to remove.
* Optionally, an array of integers may be given as a second argument.
This argument represents a range to which the removal will be limited.
* If the range contains a single integer, it will represent all members
of the queue whose index is greater than or equal to the value of the
integer.
* If the range contains two integers, it will represent all members of
the queue whose index is greater than or equal to the value of the
first integer and less than the value of the second integer.
* If the range contains more than two integers, an error will occur.
Return value: Nothing meaningful.
- boolean replace (array)
-
Replaces the contents of the queue with the given items.
This is equivalent to calling clear() and prepend() in succession, except that this
operation is atomic.
Argument: An array of (base64-encoded) strings, representing the items to be
added.
* When adding local filenames to the queue, only absolute pathnames
should be used. Using relative pathnames would be foolish because
the server isn't aware of the client's current working directory.
Return value: Nothing meaningful.
- boolean reverse ()
- boolean reverse (array)
-
Reverses the order of the items in the queue.
Arguments: Either none, or an array of integers that represents a range.
* If no range is given, the whole list is affected.
* If the range contains a single integer, it will represent all members
of the queue whose index is greater than or equal to the value of the
integer.
* If the range contains two integers, it will represent all members of
the queue whose index is greater than or equal to the value of the
first integer and less than the value of the second integer.
* If the range contains more than two integers, an error will occur.
Return value: Nothing meaningful.
- boolean run_queue ()
-
Allows new songs to be played again after halt_queue() has been called.
Arguments: None.
Return value: Nothing meaningful.
- boolean runqueue ()
-
Allows new songs to be played again after halt_queue() has been called.
Arguments: None.
Return value: Nothing meaningful.
- boolean set_history_limit (int)
-
Sets the limit on the size of the history list stored in memory.
This will irrevocably discard history entries if the new limit is lower than
the current size of the history list.
Arguments: The new maximum number of history entries. If this value is
negative, the history limit will be set to zero.
Return value: Nothing meaningful.
- boolean set_loop_mode (boolean)
-
Turns loop mode on or off.
If loop mode is on, songs are returned to the end of the song queue after
they finish playing. If loop mode is off, songs that have finished playing
are not returned to the queue.
Arguments: True if you want to turn loop mode on, False if you want to turn
it off.
Return value: Nothing meaningful.
- base64 showconfig ()
-
Returns a textual description of the server's player configuration.
Arguments: None.
Return value: A (base64-encoded) string that shows which programs will be
used to play the various file-types recognized by the Moosic server.
- boolean shuffle ()
- boolean shuffle (array)
-
Rearrange the contents of the queue into a random order.
Arguments: Either none, or an array of integers that represents a range.
* If no range is given, the whole list is affected.
* If the range contains a single integer, it will represent all members
of the queue whose index is greater than or equal to the value of the
integer.
* If the range contains two integers, it will represent all members of
the queue whose index is greater than or equal to the value of the
first integer and less than the value of the second integer.
* If the range contains more than two integers, an error will occur.
Return value: Nothing meaningful.
- boolean skip ()
-
Skips the rest of the current song to play the next song in the queue.
This only has an effect if there actually is a current song.
Arguments: None.
Return value: Nothing meaningful.
- boolean sort ()
- boolean sort (array)
-
Arranges the contents of the queue into sorted order.
Arguments: Either none, or an array of integers that represents a range.
* If no range is given, the whole list is affected.
* If the range contains a single integer, it will represent all members
of the queue whose index is greater than or equal to the value of the
integer.
* If the range contains two integers, it will represent all members of
the queue whose index is greater than or equal to the value of the
first integer and less than the value of the second integer.
* If the range contains more than two integers, an error will occur.
Return value: Nothing meaningful.
- boolean stop ()
-
Stops playing the current song and stops new songs from playing. The
current song is returned to the head of the song queue and is not recorded
in the history list. If loop mode is on, the current song won't be placed at
the end of the song queue when it is stopped.
Arguments: None.
Return value: Nothing meaningful.
- boolean sub (base64, base64)
- boolean sub (base64, base64, array)
-
Performs a regular expression substitution on the items in the queue.
Arguments: The first is a (base64-encoded) regular expression that specifies
the text to be replaced.
* The second argument is the (base64-encoded) string that will be used to
replace the first occurrence of the regular expression within each queue
item. Any backslash escapes in this string will be processed, including
special character translation (e.g. "\n" to newline) and backreferences
to groups within the match.
* Optionally, an array of integers may be given as a third argument.
This argument represents a range to which the substitution will be
limited. This range is interpreted in the same way as the range argument
in other Moosic methods.
* If performing a replacement changes an item in the queue into the empty
string, then it is removed from the queue.
Return value: Nothing meaningful.
- boolean sub_all (base64, base64)
- boolean sub_all (base64, base64, array)
-
Performs a global regular expression substitution on the items in the queue.
Arguments: The first is a (base64-encoded) regular expression that specifies
the text to be replaced.
* The second argument is the (base64-encoded) string that will be used to
replace all occurrences of the regular expression within each queue
item. Any backslash escapes in this string will be processed, including
special character translation (e.g. "\n" to newline) and backreferences
to the substrings matched by individual groups in the pattern.
* Optionally, an array of integers may be given as a third argument.
This argument represents a range to which the substitution will be
limited. This range is interpreted in the same way as the range argument
in other Moosic methods.
* If performing a replacement changes an item in the queue into the empty
string, then it is removed from the queue.
Return value: Nothing meaningful.
- boolean swap (array, array)
-
Swaps the items contained in one range with the items contained in the
other range.
Return value: Nothing meaningful.
- array system.listMethods ()
-
Return an array of all available XML-RPC methods on this server.
- string system.methodHelp (string)
-
Given the name of a method, return a help string.
- array system.methodSignature (string)
-
Given the name of a method, return an array of legal signatures. Each
signature is an array of strings. The first item of each signature is
the return type, and any others items are parameter types.
- array system.multicall (array)
-
Process an array of calls, and return an array of results. Calls
should be structs of the form {'methodName': string, 'params': array}.
Each result will either be a single-item array containg the result
value, or a struct of the form {'faultCode': int, 'faultString':
string}. This is useful when you need to make lots of small calls
without lots of round trips.
- boolean toggle_loop_mode ()
-
Turns loop mode on if it is off, and turns it off if it is on.
If loop mode is on, songs are returned to the end of the song queue after
they finish playing. If loop mode is off, songs that have finished playing
are not returned to the queue.
Arguments: None.
Return value: Nothing meaningful.
- boolean toggle_pause ()
-
Pauses the current song if it is playing, and unpauses if it is paused.
Arguments: None.
Return value: Nothing meaningful.
- boolean unpause ()
-
Unpauses the current song.
Arguments: None.
Return value: Nothing meaningful.
- string version ()
-
Returns the Moosic server's version string.
Arguments: None.
Return value: The version string for the Moosic server.
Section 4: Writing a Moosic Client in Python¶
As demonstrated in section 0, communicating with a Moosic server is very easy to
do with Python. In this section, I'll merely elaborate on the details that
were omitted from section 0 for the sake of brevity.
First of all, you should know that
LocalMoosicProxy() can be called with
a filename argument to specify the location of the Moosic server's socket
file. This is useful if moosicd was started with the "-c" option.
Refer to the moosic_factory.py module's documentation (moosic_factory.html).
Next, note that many of the Moosic server's methods accept or return special
types of objects from the xmlrpclib module, namely Boolean and Binary. These
object types serve the purpose of bridging the small mismatch between the
data-types supported by XML-RPC and Python's intrinsic data-types. Boolean
objects present no unusual problem, since they evaluate to a correct truth
value without any extra effort. However, you must take care when using the
Moosic methods that accept or return Binary objects. Read the documentation
for the xmlrpclib module for details on how to work with these objects. The
basic technique boils down to wrapping up a string inside a Binary object
before sending it to the server, and using the "data" attribute to
access the string data within the Binary objects returned by the server.
Regular strings can't be used because XML-RPC's normal string data-type can't
handle multiple 8-bit strings within a single request if the strings use
different encodings.
Section 5: Writing a Moosic Client in Another Language¶
If you are not using Python to write your Moosic client, the first issue to deal
with is deciding upon an XML-RPC implementation. For most popular programming
languages, there are multiple XML-RPC implementations available. Most of the
possibilities are listed at
<
http://www.xmlrpc.com/directory/1568/implementations>. Since XML-RPC is
an open specification, you can create your own implementation if you don't
like any of the ones that already exist.
Once you've got an XML-RPC library that you like, the big hurdle to overcome is
to make that library send its RPC calls over a Unix socket instead of an IP
socket. I was able to do this pretty easily with Python's xmlrpclib since it
is designed to allow pluggable transport methods: all I had to do was subclass
my own Transport type and plug it back into the original library's classes.
(If your language and/or library of choice makes this task difficult, then you
may begin to understand why some Python programmers are so smug.)
After you are capable of sending XML-RPC requests through a Unix socket, you can
go ahead and start sending requests to a Moosic server. Refer to the end of
section 2 for information on how to address a Moosic server. Refer to section
3 for a list of valid server requests.
If you can't be bothered to find or hack together an XML-RPC library that works
with Unix sockets, then you can still talk to a Moosic server that is
listening on an IP socket, but this is less than ideal since listening on an
IP socket is not default behavior for most Moosic servers.
Section 6: API Version History (ChangeLog)¶
- •
- 1.8
First implemented in moosicd 1.5.1. The following methods were added:
swap
- •
- 1.7
First implemented by moosicd 1.5.0. The following methods were added:
skip, current_time
The following methods had their behavior significantly changed:
previous, next
Specifically, the previous() method no longer activates queue
advancement if it had been disabled before. This means that calling
previous() no longer necessarily causes a song to start playing.
The next() method was changed to more closely parallel the behavior
of previous(): it takes a single optional integer argument to allow
immediate advancement by more than one song at a time, and it has an
effect even when no song is currently playing. The new skip()
method implements the exact same behavior that was previously exhibited by
next().
Last, and most importantly, the name of the default socket file for
communicating with the server via unix sockets was changed from
$CONFIG_DIR/socket-$HOSTNAME to $CONFIG_DIR/socket. If you are a Python
programmer and you use the updated moosic_factory.py file from Moosic
version 1.5.0, then you don't have to make any changes. Otherwise, you
must change your client's code to connect to the file named
"socket" instead of the file named
"socket-something.example.com". If your client only talks to the
Moosic server through TCP/IP, then you don't have to make any changes, of
course.
- •
- 1.6
First implemented by moosicd 1.4.10. The following methods were added:
getconfig
- •
- 1.5
First implemented by moosicd 1.4.6. The following methods were added:
sub, sub_all, stop
- •
- 1.4
First implemented by moosicd 1.4.5. The following methods were added:
previous
- •
- 1.3
First implemented by moosicd 1.4.4. The following methods were added:
replace, replace_range, last_queue_update
- •
- 1.2
First implemented by moosicd 1.4.2. The following methods were added:
cut_list, crop_list
- •
- 1.1
First implemented by moosicd 1.4.1. The following methods were added:
is_looping, set_loop_mode, toggle_loop_mode
- •
- 1.0
First implemented by moosicd 1.4.0. The following methods were included:
api_version, append, clear, crop, current, cut, die, filter,
get_history_limit, halt_queue, haltqueue, history, indexed_list, insert,
is_paused, is_queue_running, length, list, move, move_list, next, no_op,
pause, prepend, putback, queue_length, reconfigure, remove, reverse,
run_queue, runqueue, set_history_limit, showconfig, shuffle, sort,
system.listMethods, system.methodHelp, system.methodSignature,
system.multicall, toggle_pause, unpause, version