Secure IoT Sensor Data Transmission: Implement MQTT with TLS on ESP32

Implementing MQTT with TLS on the ESP32 using the Arduino IDE

In this tutorial, we will walk through the steps to implement MQTT with TLS on the ESP32 using the Arduino IDE. This setup will enable secure IoT sensor data transmission, ensuring that your data is encrypted during communication. You’ll learn how to prepare your development environment, configure the MQTT client, and establish a secure connection.

Prerequisites

• ESP32 development board
• Arduino IDE installed (version 1.8.13 or later)
• MQTT broker that supports TLS (e.g., Mosquitto, HiveMQ)
• Basic knowledge of C/C++ programming
• Wi-Fi network access

Parts/Tools

• ESP32 Development Board
• USB Cable for programming
• MQTT Broker (configured with TLS)
• Arduino IDE with necessary libraries

Steps

Step 1: Setup the Arduino IDE

1. Open the Arduino IDE.
2. Go to File > Preferences.
3. Add the following URL to the Additional Board Manager URLs field:

https://dl.espressif.com/dl/package_esp32_index.json

4. Go to Tools > Board > Boards Manager.
5. Search for “ESP32” and install the package.

Step 2: Install Required Libraries

1. In the Arduino IDE, go to Sketch > Include Library > Manage Libraries….
2. Search for and install the following libraries:
• Paho MQTT – For MQTT protocol support.
• WiFiClientSecure – For secure communication.

Step 3: Prepare the MQTT Client Code

1. Create a new sketch in Arduino IDE.
2. Include necessary libraries at the top of your sketch:

#include <WiFi.h>
#include <WiFiClientSecure.h>
#include <PubSubClient.h>

3. Define your Wi-Fi and MQTT broker credentials:

const char* ssid = "your_SSID";
const char* password = "your_PASSWORD";
const char* mqtt_server = "your_MQTT_BROKER";
const int mqtt_port = 8883;

Step 4: Establish Wi-Fi Connection

1. In the setup() function, initialize the Serial monitor:

Serial.begin(115200);

2. Connect to Wi-Fi:

WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi...");
}
Serial.println("Connected to WiFi");

Step 5: Configure MQTT Client with TLS

1. Initialize the WiFiClientSecure object:

WiFiClientSecure wifiClient;
wifiClient.setInsecure(); // For testing; use proper certificate for production

2. Initialize the PubSubClient:

PubSubClient client(wifiClient);

3. Set the MQTT server details:

client.setServer(mqtt_server, mqtt_port);

Step 6: Implement MQTT Connection

1. Create a reconnect() function to ensure the client stays connected:

void reconnect() {
    while (!client.connected()) {
        Serial.print("Attempting MQTT connection...");
        if (client.connect("ESP32Client")) {
            Serial.println("connected");
        } else {
            Serial.print("failed, rc=");
            Serial.print(client.state());
            delay(2000);
        }
    }
}

2. Call reconnect() in the loop:

void loop() {
    if (!client.connected()) {
        reconnect();
    }
    client.loop();
}

Step 7: Publish Sensor Data

1. In the loop() function, publish your data:

client.publish("sensor/topic", "sensor_data");

Troubleshooting

• Wi-Fi Connection Issues: Ensure your SSID and password are correct and the ESP32 is within range.
• MQTT Connection Problems: Verify that your MQTT broker is up and running and supports TLS on the specified port.
• Data Not Publishing: Check if your MQTT topic is correctly specified and ensure the client is connected before publishing.
• Secure Connection Errors: Use a valid certificate instead of wifiClient.setInsecure() in production.

Conclusion

In this tutorial, we successfully implemented MQTT with TLS on the ESP32 using the Arduino IDE. You can now securely transmit sensor data over the internet. For production applications, ensure to use proper certificates for secure communication and further refine your MQTT implementation.