Guide 2: Simulate Sensor Data with Python + MQTT

Introduction

Weather apps, smart farming systems, or IoT-based environmental monitors often depend on a steady stream of sensor data. But what if you don’t have actual sensors yet? No problem. We’ll simulate a weather station that periodically reports temperature, humidity, and pressure via MQTT.

Whether you’re prototyping a dashboard, testing a backend, or learning MQTT for the first time, this guide will help you get your feet wet without needing to touch a single sensor. Let’s roll! 🚀

Prerequisites

pip install paho-mqtt==1.6.1
                

sudo apt update
sudo apt install mosquitto mosquitto-clients
                

brew install mosquitto
brew services start mosquitto
                

"C:\Program Files\mosquitto\mosquitto.exe"
                

Simulate a Weather Station

Let’s simulate a weather station that publishes data every 5 seconds to an MQTT topic weather/station1.

Code: weather_simulator.py

import time
import random
import paho.mqtt.client as mqtt

BROKER = 'localhost'
PORT = 1883
TOPIC = 'weather/station1'

# Create client
client = mqtt.Client()
client.connect(BROKER, PORT, 60)

print("Weather station simulator started. Publishing to MQTT topic...")

while True:
    temperature = round(random.uniform(20.0, 35.0), 2)
    humidity = round(random.uniform(30.0, 70.0), 2)
    pressure = round(random.uniform(990.0, 1025.0), 2)

    message = {
        "temperature": temperature,
        "humidity": humidity,
        "pressure": pressure
    }

    client.publish(TOPIC, str(message))
    print(f"Published: {message}")
    time.sleep(5)
        

Here, we simulate temperature, humidity, and pressure readings, then publish them as a JSON-like string. Replace localhost with your broker IP if needed.

View Your Data

To verify data is arriving using the Mosquitto CLI:

mosquitto_sub -h localhost -t weather/#
        

You should see:

{"temperature": 29.53, "humidity": 55.2, "pressure": 1011.34}
        

Wrap-Up

That’s it! You now have a virtual weather station chirping out sensor readings like a seasoned meteorologist. This simulation is perfect for testing dashboards, logging data, or learning MQTT without hardware.

Next up: subscribe to this topic and store data in a CSV or database. Happy IoT hacking! ☀️☔️