Man Linux: Main Page and Category List

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 Servers 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>.
       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>,
       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