losant-mqtt 1.2.1
An MQTT client for Losant
License: MIT
Keywords: MQTT, Losant, IoT

Losant Python MQTT Client
=========================

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The `Losant <https://www.losant.com>`_ MQTT client provides a simple way for
custom things to communicate with the Losant platform over MQTT.  You can authenticate
as a device, publish device state, and listen for device commands.

This client works with both Python 2.7 and 3. It uses the
`Paho MQTT Client <https://github.com/eclipse/paho.mqtt.python>`_ under the
covers for the actual MQTT communication.

Installation
------------

The latest stable version is available in the Python Package Index (PyPi)
and can be installed using

::

    pip install losant-mqtt


Example
-------

Below is a high-level example of using the Losant Python MQTT client to send the value
of a temperature sensor to the Losant platform.

::

    import time
    from losantmqtt import Device

    # Construct device
    device = Device("my-device-id", "my-app-access-key", "my-app-access-secret")

    def on_command(device, command):
        print("Command received.")
        print(command["name"])
        print(command["payload"])

    # Listen for commands.
    device.add_event_observer("command", on_command)

    # Connect to Losant.
    device.connect(blocking=False)

    # Send temperature once every second.
    while True:
        device.loop()
        if device.is_connected():
            temp = call_out_to_your_sensor_here()
            device.send_state({"temperature": temp})
        time.sleep(1)


API Documentation
-----------------

* `Device`_
    * `constructor`_
    * `connect`_
    * `is_connected`_
    * `close`_
    * `send_state`_
    * `loop`_
    * `add_event_observer`_
    * `remove_event_observer`_

Device
******

A device represents a single thing or widget that you'd like to connect to the Losant platform.
A single device can contain many different sensors or other attached peripherals.
Devices can either report state or respond to commands.

A device's state represents a snapshot of the device at some point in time.
If the device has a temperature sensor, it might report state every few seconds
with the temperature. If a device has a button, it might only report state when
the button is pressed. Devices can report state as often as needed by your specific application.

Commands instruct a device to take a specific action. Commands are defined as a
name and an optional payload. For example, if the device is a scrolling marquee,
the command might be "update text" and the payload would include the text to update.

constructor
```````````

::

    Device(device_id, key, secret, secure=True, transport="tcp")

The ``Device()`` constructor takes the following arguments:

device_id
    The device's ID. Obtained by first registering a device using the Losant platform.

key
    The Losant access key.

secret
    The Losant access secret.

secure
    If the client should connect to Losant over SSL - default is true.

transport
    Allowed values are "tcp" and "websockets". Defaults to "tcp", which is a raw TCP connection over
    ports 1883 (insecure) or 8883 (secure). When "websockets" is passed in, connects using MQTT over
    WebSockets, which uses either port 80 (insecure) or port 443 (secure).

Example
.......

::

    from losantmqtt import Device

    device = Device("my-device-id", "my-app-access-key", "my-app-access-secret")

connect
```````

::

    connect(blocking=True)

Connects the device to the Losant platform. Hook the connect event to know when a connection
has been successfully established.  Connect takes the following arguments:

blocking
    If the connect method should block or not.  True is the default, which means that the connect
    call will be a blocking call that will not return until the connection is closed or an error
    occurs - all interaction has to be done through the various event callbacks.  If blocking is
    set to False, the function will only block until the connection is kicked off - after that point
    you must run the network loop yourself, by calling the `loop`_ method periodically.

is_connected
````````````

::

    is_connected()

Returns a boolean indicating whether or not the device is currently connected
to the Losant platform.

close
`````

::

    close()

Closes the device's connection to the Losant platform.

send_state
``````````

::

    send_state(state, time_like=None)

Sends a device state to the Losant platform. In many scenarios, device states will
change rapidly. For example a GPS device will report GPS coordinates once a second or
more. Because of this, sendState is typically the most invoked function. Any state
data sent to Losant is stored and made available in data visualization tools
and workflow triggers.

state
    The state to send as a Dict.

time_like
    When the state occurred - if None or not set, will default to now.

Example
.......

::

    device.send_state({ "voltage": read_analog_in() })

loop
`````

::

    loop(timeout=1)

Loops the network stack for the connection.  Only valid to call when connected in non-blocking mode.
Be sure to call this reasonably frequently when in that model to make sure the underlying
MQTT connection does not get timed out.

timeout
    Max time to block on the socket before continuing - defaults to 1 second.

add_event_observer
``````````````````

::

    add_event_observer(event_name, observer)

Adds an observer to listen for an event on this device.

event_name
    The event to listen for.  Possible events are: "connect" (the device has connected),
    "reconnect" (the device lost its connection and reconnected),
    "close" (the device's connection was closed), and
    "command" (the device has received a command from Losant).

observer
    Callback method to call when the given event fires.  The first argument for all callbacks
    will be the device instance.  Command callbacks have a second argument - the command
    received.


Example
.......

::

    def on_command(device, cmd):
        print(cmd["time"]) # time of the command
        print(cmd["name"]) # name of the command
        print(cmd["payload"]) # payload of the command

    device.add_event_observer("command", on_command)

remove_event_observer
`````````````````````

::

    remove_event_observer(event_name, observer)

Removes an observer from listening for an event on this device.

event_name
    The event to stop listening for.  Same events as `add_event_observer`_.

observer
    Callback method to remove.


Copyright (c) 2024 Losant IoT, Inc

https://www.losant.com