Coverage for tutorials/ngsi_v2/e1_virtual_weatherstation/e1_virtual_weatherstation_solution.py: 0%
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« prev ^ index » next coverage.py v7.10.2, created at 2025-08-05 11:07 +0000
1"""
2# # Exercise 1: Virtual Weather-Station
4# Create a virtual IoT device that simulates the ambient temperature and
5# publishes it via MQTT. The simulation function is already predefined.
6# This exercise gives a simple introduction to the communication via MQTT.
8# The input sections are marked with 'ToDo'
10# #### Steps to complete:
11# 1. Set up the missing parameters in the parameter section
12# 2. Create an MQTT client using the paho-mqtt package with mqtt.Client()
13# 3. Define a callback function that will be executed when the client
14# receives message on a subscribed topic. It should decode your message
15# and store the information for later in our history
16# `history_weather_station`
17# 4. Subscribe to the topic that the device will publish to
18# 5. Create a function that publishes the simulated temperature `t_amb` and
19# the corresponding simulation time `t_sim `via MQTT as a JSON
20# 6. Run the simulation and plot
21"""
23# ## Import packages
24import json
25import time
26from urllib.parse import urlparse
27from uuid import uuid4
28import matplotlib.pyplot as plt
29import paho.mqtt.client as mqtt
31# import simulation model
32from tutorials.ngsi_v2.simulation_model import SimulationModel
34# ## Parameters
35# ToDo: Enter your mqtt broker url and port, e.g. mqtt://test.mosquitto.org:1883.
36MQTT_BROKER_URL = "mqtt://test.mosquitto.org:1883"
37# ToDo: If required, enter your username and password.
38MQTT_USER = ""
39MQTT_PW = ""
41# ToDo: Create a unique topic that your weather station will publish on,
42# e.g. by using a uuid.
43UNIQUE_ID = str(uuid4())
44TOPIC_WEATHER_STATION = f"fiware_workshop/{UNIQUE_ID}/weather_station"
46# set parameters for the temperature simulation
47TEMPERATURE_MAX = 10 # maximal ambient temperature
48TEMPERATURE_MIN = -5 # minimal ambient temperature
50T_SIM_START = 0 # simulation start time in seconds
51T_SIM_END = 24 * 60 * 60 # simulation end time in seconds
52COM_STEP = 60 * 60 # 60 min communication step in seconds
54# ## Main script
55if __name__ == "__main__":
56 # instantiate simulation model
57 sim_model = SimulationModel(
58 t_start=T_SIM_START,
59 t_end=T_SIM_END,
60 temp_max=TEMPERATURE_MAX,
61 temp_min=TEMPERATURE_MIN,
62 )
64 # define a list for storing historical data
65 history_weather_station = []
67 # ToDo: Create an MQTTv5 client with paho-mqtt.
68 mqttc = mqtt.Client(
69 protocol=mqtt.MQTTv5, callback_api_version=mqtt.CallbackAPIVersion.VERSION2
70 )
71 # set user data if required
72 mqttc.username_pw_set(username=MQTT_USER, password=MQTT_PW)
74 # ToDo: Define a callback function that will be executed when the client
75 # receives message on a subscribed topic. It should decode your message
76 # and store the information for later in our history.
77 # Note: Do not change the function's signature!
78 def on_message(client, userdata, msg):
79 """
80 Callback function for incoming messages
81 """
82 # decode the payload
83 payload = msg.payload.decode("utf-8")
84 # ToDo: Parse the payload using the `json` package and write it to
85 # the history.
86 history_weather_station.append(json.loads(payload))
88 # add your callback function to the client. You can either use a global
89 # or a topic specific callback with `mqttc.message_callback_add()`
90 mqttc.on_message = on_message
92 # ToDo: Connect to the mqtt broker and subscribe to your topic.
93 mqtt_url = urlparse(MQTT_BROKER_URL)
94 mqttc.connect(
95 host=mqtt_url.hostname,
96 port=mqtt_url.port,
97 keepalive=60,
98 bind_address="",
99 bind_port=0,
100 clean_start=mqtt.MQTT_CLEAN_START_FIRST_ONLY,
101 properties=None,
102 )
104 # ToDo: Print and subscribe to the weather station topic.
105 print(f"WeatherStation topic:\n {TOPIC_WEATHER_STATION}")
106 mqttc.subscribe(topic=TOPIC_WEATHER_STATION)
108 # create a non-blocking thread for mqtt communication
109 mqttc.loop_start()
111 # ToDo: Create a loop that publishes every 0.2 seconds a message to the broker
112 # that holds the simulation time "t_sim" and the corresponding temperature
113 # "t_amb".
114 for t_sim in range(
115 sim_model.t_start, int(sim_model.t_end + COM_STEP), int(COM_STEP)
116 ):
117 # ToDo: Publish the simulated ambient temperature.
118 mqttc.publish(
119 topic=TOPIC_WEATHER_STATION,
120 payload=json.dumps({"t_amb": sim_model.t_amb, "t_sim": sim_model.t_sim}),
121 )
123 # simulation step for next loop
124 sim_model.do_step(int(t_sim + COM_STEP))
125 time.sleep(0.2)
127 # close the mqtt listening thread
128 mqttc.loop_stop()
129 # disconnect the mqtt device
130 mqttc.disconnect()
132 # plot results
133 fig, ax = plt.subplots()
134 t_simulation = [item["t_sim"] / 3600 for item in history_weather_station]
135 temperature = [item["t_amb"] for item in history_weather_station]
136 ax.plot(t_simulation, temperature)
137 ax.set_xlabel("time in h")
138 ax.set_ylabel("ambient temperature in °C")
139 plt.show()