# 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).