<?xml version='1.0' encoding='UTF-8'?> <!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "docbook/xml-dtd-4.2-1.0-24/docbookx.dtd" []> <article> <title>MPD Protocol</title> <articleinfo> <releaseinfo>Version 0.11.0</releaseinfo> <copyright> <year>2004</year> <holder>Warren Dukes</holder> </copyright> </articleinfo> <sect1> <title>Protocol Outline</title> <para>The MPD Protocol has Three Components: Commands, Responses, and Command Lists. All communication between the client and server uses the UTF-8 character encoding.</para> <sect2> <title>Format of Commands</title> <para>Commands in MPD are specified begginning with the name of the command. The arguments of a command are delimitted by spaces and should be surrounded by double qutotation marks. The end of a command is delimitted by a return character '<literal>\n</literal>'.<programlisting>command "arg1" "arg2"</programlisting></para> </sect2> <sect2> <title>Format of Responses</title> <para>The different response elements of a command are seperated by the return character '<literal>\n</literal>'. The last element of a response begin with either <literal>OK</literal> or <literal>ACK</literal>. Thus, if a command is successful, the end of the response is <literal>OK\n</literal>. If a command is unsuccessful <literal>ACK</literal> terminates the command with the following format:<programlisting>ACK {err#:cmd#} {command} some error message</programlisting><literal>err#</literal> is an integer indicating the specific error that occured and <literal>cmd#</literal> is an integer indicating which command of the command list caused the error (See section 1.3 for more info on Command Lists). <literal>command</literal> gives the name of the command the error occurred on; however, its intended more for debugging persons (for human readability). <literal>some error message</literal> is also not intended to be parsed by clients but is intended more for debugging purposes.</para> <para>The other response elements are data. The data is seperated into a name and value pare by <literal>: </literal>. Thus, a possible command response containing data would be:<programlisting>Name1: Value1 Name2: Value2 OK</programlisting></para> </sect2> <sect2> <title>Command Lists</title> <para>Command lists allow for a fast, effecient, and atomic execution of multiple commands. Command lists are initiated with either <literal>command_list_begin</literal> or <literal>command_list_ok_begin</literal>and are terminated with <literal>command_list_end</literal>.<programlisting>command_list_begin command1 arg1 arg2 command2 arg1 arg2 command3 arg1 arg2 command_list_end</programlisting></para> <para>The responses for command executed with command lists are the same with the exception that an<literal>OK</literal> or <literal>ACK</literal> is not returned for each command. Instead a single <literal>OK</literal> or <literal>ACK</literal> is returned for the entire command list. An <literal>OK</literal> indicates that all the commands in the command list were successfully executed; while an <literal>ACK</literal> error is returned on the first unsuccessful command in the command list and none of the following commands in the command are executed.</para> <para><literal>command_list_ok_begin</literal> responds with <literal>list_OK</literal> after each command is successfully completed. <literal>command_list_begin</literal> does not return anything between each command that is executed.</para> </sect2> </sect1> <sect1> <title>Commands</title> <sect2> <title>DB: Browsing, Searching, and Finding</title> <sect3> <title>Browsing Responses</title> <para>Browsing Responses usually contain groups of several responses. These groups are either begin with <literal>file</literal>, <literal>directory</literal>, or <literal>playlist</literal>. Each of these response groups maybe followed by metadata, which always begin with a capital letter (A-Z). Here's an example of a complete browsing response:<programlisting>file: Directory/file.mp3 Artist: Muscian Album: Record Time: 23 directory: Directory/Subdirectory playlist: Directory/favorites OK</programlisting></para> <para><literal>directory</literal> and <literal>playlist</literal> have no metadata, however future versions of the MPD protocol may add metadata to either. Also, future versions of MPD may add othe response groups for browsing.</para> </sect3> <sect3> <title>Song Info Responses</title> <para>For query information on songs in the db (and the playlist), there is a common response for each song. The first response element is <literal>file</literal>. The remainng elements of the song info are one of the following metadata types: <literal>Artist</literal>, <literal>Album</literal>, <literal>Title</literal>, <literal>Track</literal>, <literal>Name</literal>, or <literal>Time</literal>.</para> </sect3> <sect3> <title> <literal>lsinfo</literal> </title> </sect3> <sect3> <title> <literal>listall</literal> </title> </sect3> <sect3> <title> <literal>search</literal> </title> </sect3> <sect3> <title> <literal>find</literal> </title> </sect3> <sect3> <title> <literal>list</literal> </title> </sect3> </sect2> <sect2> <title>Playlist: Adding, Deleting, and Managment</title> <sect3> <title>Additional Song Metadata</title> </sect3> <sect3> <title>Song ID's vs Playlist Position</title> </sect3> <sect3> <title> <literal>playlistinfo</literal> </title> </sect3> <sect3> <title> <literal>playlistid</literal> </title> </sect3> <sect3> <title> <literal>plchanges</literal> </title> </sect3> <sect3> <title> <literal>deleteid</literal> </title> </sect3> <sect3> <title> <literal>delete</literal> </title> </sect3> <sect3> <title> <literal>add</literal> </title> </sect3> <sect3> <title> <literal>moveid</literal> </title> </sect3> <sect3> <title> <literal>move</literal> </title> </sect3> <sect3> <title> <literal>swapid</literal> </title> </sect3> <sect3> <title> <literal>swap</literal> </title> </sect3> <sect3> <title> <literal>clear</literal> </title> </sect3> <sect3> <title> <literal>save</literal> </title> </sect3> <sect3> <title> <literal>shuffle</literal> </title> </sect3> <sect3> <title> <literal>rm</literal> </title> </sect3> </sect2> <sect2> <title>Status Queries</title> <sect3> <title> <literal>status</literal> </title> </sect3> </sect2> <sect2> <title>Playback: Play, Pause, Stop, and Seek</title> <sect3> <title> <literal>playid</literal> </title> </sect3> <sect3> <title> <literal>play</literal> </title> </sect3> <sect3> <title> <literal>pause</literal> </title> </sect3> <sect3> <title> <literal>stop</literal> </title> </sect3> <sect3> <title> <literal>seekid</literal> </title> </sect3> <sect3> <title> <literal>seek</literal> </title> </sect3> <sect3> <title> <literal>repeat</literal> </title> </sect3> <sect3> <title> <literal>random</literal> </title> </sect3> </sect2> <sect2> <title>Miscellanous Commands</title> <sect3> <title> <literal>password</literal> </title> </sect3> <sect3> <title> <literal>stats</literal> </title> </sect3> <sect3> <title> <literal>kill</literal> </title> </sect3> </sect2> </sect1> <sect1> <title>ACK Errors</title> <sect2> <title>Common Errors</title> </sect2> <sect2> <title>Command Specific</title> </sect2> </sect1> <sect1> <title>Guidelines</title> </sect1> </article>