Solving the Mystery: Why Your ESP32 MQTT Messages aren’t Reaching RabbitMQ Queue

Are you scratching your head, wondering why your ESP32 device is sending MQTT messages that seem to disappear into thin air, never to be seen again in your RabbitMQ queue? You’re not alone! In this article, we’ll dive into the common pitfalls and provide a step-by-step guide to ensure your messages reach their destination.

The Setup: ESP32, MQTT, and RabbitMQ

Before we begin, let’s assume you have a basic understanding of the technologies involved:

• ESP32: A microcontroller with built-in Wi-Fi and Bluetooth capabilities, perfect for IoT projects.
• MQTT (Message Queuing Telemetry Transport): A lightweight messaging protocol ideal for low-bandwidth, high-latency networks.
• RabbitMQ: A popular open-source message broker that enables scalable, distributed message processing.

The Problem: Messages not reaching RabbitMQ queue

When sending MQTT messages from your ESP32 device, you might observe that they’re not being consumed by RabbitMQ. But, when you use a tool like mosquitto_sub to subscribe to the same topic, the messages are received just fine. What’s going on?

Possible Causes:

Let’s explore some common reasons why your messages might not be reaching RabbitMQ:

• Incorrect MQTT topic or QoS: Double-check that your ESP32 is publishing to the correct topic and using the desired QoS (Quality of Service) level.
• RabbitMQ configuration issues: Ensure that RabbitMQ is properly configured to accept MQTT messages and that the MQTT plugin is enabled.
• Network connectivity problems: Verify that your ESP32 is connected to the same network as RabbitMQ and that there are no firewall rules blocking the communication.
• Authentication and authorization: Make sure that your ESP32 is using the correct credentials and permissions to publish to RabbitMQ.

Troubleshooting and Solution

Let’s go through a series of steps to troubleshoot and solve the issue:

Step 1: Verify ESP32 MQTT Configuration

Review your ESP32 code to ensure that:

• The MQTT library is correctly configured and initialized.
• The device is connected to the same MQTT broker as RabbitMQ.
• The topic, QoS, and other publishing parameters are correct.

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

const char* mqttServer = "mqtt.example.com";
const char* topic = "home/livingRoom/temp";

WiFiClient espClient;
PubSubClient client(espClient);

void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi...");
  }

  Serial.println("Connected to WiFi");
  client.setServer(mqttServer, 1883);
}

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

  // Publish a message to the topic
  client.publish(topic, "Hello from ESP32!");
  delay(5000);
}

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());
      Serial.println(" try again in 5 seconds");
      delay(5000);
    }
  }
}

Step 2: Check RabbitMQ Configuration

Verify that RabbitMQ is properly configured to accept MQTT messages:

• Enable the MQTT plugin in RabbitMQ (e.g., rabbitmq-plugins enable rabbitmq_mqtt).
• Configure the MQTT adapter to listen on the correct port (e.g., 1883).
• Create a new exchange (e.g., mqtt_exchange) and bind it to the MQTT adapter.
• Create a new queue (e.g., mqtt_queue) and bind it to the exchange.

RabbitMQ Configuration	Command
Enable MQTT plugin	rabbitmq-plugins enable rabbitmq_mqtt
Configure MQTT adapter	rabbitmqctl set_listener TCP:1883 mqtt
Create exchange	rabbitmqctl add_exchange mqtt_exchange fanout
Bind exchange to MQTT adapter	rabbitmqctl bind_exchange_queue mqtt_exchange mqtt_queue
Create queue	rabbitmqctl add_queue mqtt_queue
Bind queue to exchange	rabbitmqctl bind_queue mqtt_queue mqtt_exchange "" mqtt_queue

Step 3: Verify Network Connectivity

Ensure that your ESP32 device and RabbitMQ broker are connected to the same network:

• Check that both devices are connected to the same Wi-Fi network or are on the same LAN.
• Verify that there are no firewall rules blocking the communication between the devices.

Step 4: Authenticate and Authorize

Make sure that your ESP32 device is using the correct credentials and permissions to publish to RabbitMQ:

• Verify that the MQTT username and password are correct and match the RabbitMQ configuration.
• Ensure that the ESP32 device has the necessary permissions to publish to the RabbitMQ exchange.

// Update the reconnect function to include MQTT credentials
void reconnect() {
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    if (client.connect("ESP32Client", "mqtt_username", "mqtt_password")) {
      Serial.println(" connected");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      delay(5000);
    }
  }
}

Conclusion

By following these steps, you should be able to identify and resolve the issues preventing your ESP32 MQTT messages from reaching your RabbitMQ queue. Remember to double-check your configuration, network connectivity, and authentication parameters.

Now, you should be able to enjoy seamless message exchange between your ESP32 device and RabbitMQ, unlocking the full potential of your IoT application.

Frequently Asked Question

If you’re having trouble getting messages to reach your RabbitMQ queue when sending them from an ESP32 via MQTT, but can consume them live, don’t worry – we’ve got you covered!