Callback server

LMSCallbackServer provides a mechanism for subscribing to event notifications from the server and triggering callback functions based on the type of event received.

The server subclasses the python threading so that the server can be run in the background.

Event notifications

The callback server will send a single parameter to the callback function. This parameter is the event payload. Therefore any method that is to be used as a callback function should be able to accept (and handle) this payload.

Notification payload

The payload is a single string and must be parsed by your callback function.

An example payload looks like this:

41:41:41:41:41:41 mixer volume -5

The first part of the payload is the reference of the player, the remaining part is the relevant event.

If you need to check whether the event matches a specific player you can check equivalence via the ref property or just compare the player reference received with the player object. e.g.:

>>>laptop = LMSPlayer("41:41:41:41:41:41", server)
>>>event = "41:41:41:41:41:41 mixer volume -5"
>>>event_player = event.split(" ")[0]
>>>event_player == laptop.ref
True
>>>event_player == laptop
True

Alternatively, the player can check the event itself via the check_event_player or check_event_sync_group methods.

>>>laptop = LMSPlayer("41:41:41:41:41:41", server)
>>>event = "41:41:41:41:41:41 mixer volume -5"
>>>laptop.check_event_player(event)
True

Using the callbackserver

Callbacks can be configured in two different ways:

1. Using decorators
2. Using the add_callback method

Decorators

squeeze = LMSCallbackServer()

@squeeze.event(squeeze.VOLUME_CHANGE)
def volume_event(event=None):
    print "Volume event received: {}".format(event)

squeeze.set_server("192.168.0.1")
squeeze.start()

If you are using decorators inside a class then this will happen before your class has been initialised so you need to provide the callback server with a reference to the class instance.

squeeze = LMSCallbackServer()

class MyClass(object):

    def __init__(self):
        self.squeeze = squeeze
        self.squeeze.set_server("192.168.0.1", parent_class=self)
        self.squeeze.start()

    @squeeze.event(squeeze.VOLUME_CHANGE)
    def volume_event(self, event=None):
        print "Volume event received: {}".format(event)

Multiple events can be added with multiple decorators

@squeeze.event(squeeze.VOLUME_CHANGE)
@squeeze.event(squeeze.PLAY_PAUSE)
def generic_event(event=None):
    print "Event received: {}".format(event)

Or by passing events as a list

@squeeze.event([squeeze.VOLUME_CHANGE, squeeze.PLAY_PAUSE])
def generic_event(event=None):
    print "Event received: {}".format(event)

Using ‘add_callback’ method

def volume_event(event=None):
    print "Volume event received: {}".format(event)

squeeze = LMSCallbackServer("192.168.0.1")
squeeze.add_callback(squeeze.VOLUME_CHANGE, volume_event)
squeeze.start()