Using the client library

Introduction

The client library can be used as follows:

client = musicpd.MPDClient()       # create client object
client.connect()                   # use MPD_HOST/MPD_PORT if set else
                                   #   test ${XDG_RUNTIME_DIR}/mpd/socket for existence
                                   #   fallback to localhost:6600
                                   # connect support host/port argument as well
print(client.mpd_version)          # print the mpd protocol version
print(client.cmd('foo', 42))       # print result of the request "cmd foo 42"
                                   # (nb. for actual command, see link to the protocol below)
client.disconnect()                # disconnect from the server

In the example above cmd in not an actual MPD command, for a list of supported commands, their arguments (as MPD currently understands them), and the functions used to parse their responses see Available commands.

See the MPD protocol documentation for more details.

Environment variables

The client honors the following environment variables:

  • MPD_HOST MPD host (FQDN, socket path or abstract socket) and password.

    To define a password set MPD_HOST to “password@host” (password only “password@”)
    For abstract socket use “@” as prefix : “@socket” and then with a password “pass@@socket
    Regular unix socket are set with an absolute path: “/run/mpd/socket
  • MPD_PORT MPD port, relevant for TCP socket only, ie with FQDN defined host

  • MPD_TIMEOUT timeout for connecting to MPD and waiting for MPD’s response in seconds

  • XDG_RUNTIME_DIR path to look for potential socket: ${XDG_RUNTIME_DIR}/mpd/socket

Defaults settings

  • If MPD_HOST is not set, then look for a socket in ${XDG_RUNTIME_DIR}/mpd/socket

  • If there is no socket use localhost

  • If MPD_PORT is not set, then use 6600

  • If MPD_TIMEOUT is not set, then uses musicpd.CONNECTION_TIMEOUT

Command lists

Command lists are also supported using command_list_ok_begin() and command_list_end() :

client.command_list_ok_begin()       # start a command list
client.update()                      # insert the update command into the list
client.status()                      # insert the status command into the list
results = client.command_list_end()  # results will be a list with the results

Ranges

Provide a 2-tuple as argument for command supporting ranges (cf. MPD protocol documentation for more details). Possible ranges are: “START:END”, “START:” and “:” :

# An intelligent clear
# clears played track in the queue, currentsong included
pos = client.currentsong().get('pos', 0)
# the 2-tuple range object accepts str, no need to convert to int
client.delete((0, pos))
# missing end interpreted as highest value possible, pay attention still need a tuple.
client.delete((pos,))  # purge queue from current to the end

A notable case is the rangeid command allowing an empty range specified as a single colon as argument (i.e. sending just “:”):

# sending "rangeid :" to clear the range, play everything
client.rangeid(())  # send an empty tuple

Empty start in range (i.e. “:END”) are not possible and will raise a CommandError.

Iterators

Commands may also return iterators instead of lists if iterate is set to True:

client.iterate = True
for song in client.playlistinfo():
    print song['file']

Idle prefixed commands

Each command have a send_<CMD> and a fetch_<CMD> variant, which allows to send a MPD command and then fetch the result later. This is useful for the idle command:

>>> client.send_idle()
# do something else or use function like select()
# http://docs.python.org/howto/sockets.html#non-blocking-sockets
# ex. select([client], [], [])
>>> events = client.fetch_idle()

# more complex use for example, with glib/gobject:
>>> def callback(source, condition):
>>>    changes = client.fetch_idle()
>>>    print changes
>>>    return False  # removes the IO watcher

>>> client.send_idle()
>>> gobject.io_add_watch(client, gobject.IO_IN, callback)
>>> gobject.MainLoop().run()

Fetching binary content (cover art)

Fetching album covers is possible with albumart, here is an example:

>>> cli = musicpd.MPDClient()
>>> cli.connect()
>>> track = "Steve Reich/1978-Music for 18 Musicians"
>>> aart = cli.albumart(track, 0)
>>> received = int(aart.get('binary'))
>>> size = int(aart.get('size'))
>>> with open('/tmp/cover', 'wb') as cover:
>>>     # aart = {'size': 42, 'binary': 2051, data: bytes(...)}
>>>     cover.write(aart.get('data'))
>>>     while received < size:
>>>         aart = cli.albumart(track, received)
>>>         cover.write(aart.get('data'))
>>>         received += int(aart.get('binary'))
>>>     if received != size:
>>>         print('something went wrong', file=sys.stderr)
>>> cli.disconnect()

A CommandError is raised if the album does not expose a cover.

You can also use readpicture command to fetch embedded picture:

>>> cli = musicpd.MPDClient()
>>> cli.connect()
>>> track = 'muse/Amon Tobin/2011-ISAM/01-Amon Tobin - Journeyman.mp3'
>>> rpict = cli.readpicture(track, 0)
>>> if not rpict:
>>>     print('No embedded picture found', file=sys.stderr)
>>>     sys.exit(1)
>>> size = int(rpict['size'])
>>> done = int(rpict['binary'])
>>> with open('/tmp/cover', 'wb') as cover:
>>>     cover.write(rpict['data'])
>>>     while size > done:
>>>         rpict = cli.readpicture(track, done)
>>>         done += int(rpict['binary'])
>>>         print(f'writing {rpict["binary"]}, done {100*done/size:03.0f}%')
>>>         cover.write(rpict['data'])
>>> cli.disconnect()

Refer to MPD protocol documentation for the meaning of binary, size and data.

Socket timeout

Note

When the timeout is reached it raises a socket.timeout exception. An OSError subclass.

A timeout is used for the initial MPD connection (connect command), then the socket is put in blocking mode with no timeout. Its value is set in musicpd.CONNECTION_TIMEOUT at module level and musicpd.MPDClient.mpd_timeout in MPDClient instances . However it is possible to set socket timeout for all command setting musicpd.MPDClient.socket_timeout attribute to a value in second.

Having socket_timeout enabled can help to detect “half-open connection”. For instance loosing connectivity without the server explicitly closing the connection (switching network interface ethernet/wifi, router down, etc…).

Nota bene: with socket_timeout enabled each command sent to MPD might timeout. A couple of seconds should be enough for commands to complete except for the special case of idle command which by definition “ waits until there is a noteworthy change in one or more of MPD’s subsystems.” (cf. MPD protocol documentation).

Here is a solution to use idle command with socket_timeout:

import musicpd
import select
import socket

cli = musicpd.MPDClient()
try:
    cli.socket_timeout = 10  # seconds
    select_timeout = 5 # second
    cli.connect()
    while True:
        cli.send_idle()  # use send_ API to avoid blocking on read
        _read, _, _ = select.select([cli], [], [], select_timeout)
        if _read:  # tries to read response
            ret = cli.fetch_idle()
            print(', '.join(ret))  # Do something
        else: # cancels idle
            cli.noidle()
except socket.timeout as err:
    print(f'{err} (timeout {cli.socket_timeout})')
except KeyboardInterrupt:
    pass

Some explanations:

  • First launch a non blocking idle command. This call do not wait for a response to avoid socket timeout waiting for an MPD event.

  • select waits for something to read on the socket (the idle response in this case), returns after select_timeout seconds anyway.

  • In case there is something to read read it using fetch_idle

  • Nothing to read, cancel idle with noidle

All three commands in the while loop (send_idle, fetch_idle, noidle) are not triggering a socket timeout unless the connection is actually lost (actually it could also be that MPD took to much time to answer, but MPD taking more than a couple of seconds for these commands should never occur).