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Setting up your MQTT scenario

Tip

On this documentation page, code blocks can contain helpful annotations in form of a circular plus symbol: 

# try clicking the (+) symbol! (1)

  1. This dialog contains additional information about the code.

If you want to set up your own MQTT scenario, you can use the src/main.py file to add new devices. The most basic MQTT scenario without any devices can be seen here:

from application import App

config = { # (1)
    "host": "localhost",
    "port": 1883,
    "keepalive": 60,
}

app = App(config)
app.run() # Start GUI

# this part runs when the GUI is closed by the user
print("GUI was closed")
  1. This dictionary is used to configure the connection to the MQTT broker. If you use a public one, be sure to edit the hostname and port. Authentication with username and password is currently not supported.

To add a new device, call the Constructor of the device and add it with add_device to the application, as seen in the following code block:

# ...
from device_thermometer import DeviceThermometer, DeviceThermometerView

t = DeviceThermometer(config, "my_house", "living_room", "thermometer") # what do the strings mean? (2)
app.add_device(t, DeviceThermometerView) # caution: (1)
  1. When adding a device, be sure to pass a reference to the view class, not a instance! You can pass a class reference by typing the name of the class without parentheses (), for example DeviceThermometerView.
  2. The strings are used in the MQTT Topic to describe in which house and room the device is located and how the device is called.

If you want to add multiple devices, you can create different variables to store the devices or call the constructor directly in add_device:

h_id = "my_house"
r_id = "living_room"

# create multiple devices in variables ...
w0 = DeviceWindow(config, h_id, r_id, "window0")
w1 = DeviceWindow(config, h_id, r_id, "window1")
app.add_device(w0, DeviceWindowView)
app.add_device(w1, DeviceWindowView)

# ... or add them directly
app.add_device(DeviceLamp(config, h_id, r_id, "lamp0"), DeviceLampView)
app.add_device(DeviceLamp(config, h_id, r_id, "lamp1"), DeviceLampView)

After you've added some devices to the scenario, sensor devices can publish data. However, actuator devices are not able to react to published sensor data. Continue with the next guide to implement interactions between sensor and actuator devices.