Dryad API - MQTT Sensor Data Integration

Dryad External MQTT Broker

The Dryad External Message Queuing Telemetry Transport (MQTT) broker facilitates the integration of its sensor data with third-party systems. This includes customers and partners who wish to integrate the Dryad cloud platform with their own IT systems, such as command and control systems, and other data analytics platforms. For instance, this integration can be utilized for weather data analysis.

The MQTT is based on publish/subscribe architecture. It consists of an MQTT broker and MQTT clients. The term client refers to both publishers (sensors) and subscribers (third-party systems) for messages.

Dryad sensors, such as wildfire sensors, publish sensor readings to the Dryad external MQTT broker. The MQTT broker keeps track of subscribers who have subscribed to different topics. When the broker receives a message on a specific topic, it distributes the message to all subscribers who subscribe to it.

For example, a wildfire sensor might publish its sensor readings to the topic /sensor/envmon/site1/sensor1. If a subscriber (client) has subscribed to the same topic, it will receive the same message. The message contains a payload (the actual sensor data) and metadata.

Connect

The connection is initiated when the client sends a CONNECT message to the Dryad external MQTT broker. The broker responds with a CONNACK message. Once the connection is established, the broker maintains it until either the client initiates a disconnect command or the connection is interrupted.

The CONNACK message contains a return code indicating whether the connection is successful or not. Please refer to the official MQTT documentation’s Connect Reason Code section to find out the possible return (reason) codes.

Subscribe

To receive messages on topics of interest as a client, you must first send a SUBSCRIBE message to the Dryad external MQTT broker. The SUBSCRIBE message can have a packet identifier and a list of subscriptions. Each subscription contains a topic and a QoS level.

To confirm each subscription, the Dryad MQTT broker sends a SUBACK acknowledgement message to you.

The SUBACK message contains the packet identifier of the original SUBSCRIBE message and a return code. The return code indicates whether the subscription has been granted or rejected. Please refer to the official MQTT documentation's SUBACK payload section to find out the possible return (reason) codes.

After receiving the SUBACK message, you will start receiving messages that match the topics you subscribed to when they were published.

Unsubscribe

If you no longer want to receive messages on a topic, you can send a UNSUBSCRIBE message to the Dryad external MQTT broker. With the UNSUBSCRIBE message, you must include a list of topics you want to unsubscribe from. To confirm the unsubscribe, the Dryad external MQTT broker sends a UNSUBACK acknowledgement message to you.

MQTT Client Configuration

To subscribe to topics and receive messages, you'll need an MQTT client to connect with the Dryad external MQTT broker. You can configure your MQTT client to communicate with the Dryad external MQTT broker based on one of the following options:

Credentials

The site serial ID, username, and password will be provided separately via email with the username and password shared via a 1Password link. The 1Password link is valid for a period of 7 days.

Secure Port

If your client supports Secure Socket Layer (SSL) connection mode, use that mode to communicate with the Dryad eternal MQTT broker whenever possible. The secure port uses SSL certificates generated by Let’s Encrypt. The ISRG Root X1 Certificate Authority (CA) certificate is available here and can be used for a secure connection. You can specify the file location of the isrgrootx1.pem when you connect to the broker with the secure port, 31393.

QoS

Dryad uses the default Quality of Service (QoS) level, which is QoS level 0 (delivery at most once) when publishing messages. So the maximum level of QoS the subscriber can expect is also 0. Read the Eclipse Mosquitto MQTT man page for more information.

Dryad MQTT Topics

This section describes all the Dryad external MQTT topics that you can subscribe to, either insecurely or securely, along with examples:

Receive All Sensor Data from a Site

Use the topic Receive All Sensor Data from a Site to receive messages from all sensors deployed on a site. You will receive one sensor data reading at a time on the same MQTT topic.

/sensor/envmon/<site serial id>/#

For example, to receive all sensor data from the site xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx, the topic is as follows:

/sensor/envmon/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/#

The JSON payload of the message you will receive looks something like this (Please note that every time the payload you receive contains data from a single wildfire sensor):

{
    "siteId": "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx",
    "applicationNSId": "xxxxxxxx-xxxx-xxxx-xxxx-x",
    "sensorNSId": "sn-silvav2nxxx-xxxxxxxx-xxxx-xxxx-xx",
    "time": "2024-03-07T16:54:34.106672Z",
    "fireAlertStatus": 0,
    "temperature": 25.7,
    "humidity": 30,
    "airPressure": 67101.0,
    "latitude": 38.1714972222,
    "longitude": 23.7332222222,
    "batteryPct":98,
    "airQuality":659.0
  }

The table below explains each field in the JSON payload.

MQTT Clients

Dryad supports many commonly used MQTT clients. Currently, instructions for using the following MQTT clients are provided:

• Eclipse Mosquitto

• MQTTx

More to be added.

Eclipse Mosquitto

Eclipse Mosquitto's mosquitto_sub is part of the Mosquitto MQTT broker. With mosquitto_sub, you can subscribe to topics and also unsubscribe from topics.

Subscribe

With mosquitto_sub, the command syntax for subscribing to a topic is as follows:

mosquitto_sub -h <hostname> -p <port> -u <username> -P <password> [-–cafile <path_to_ca_cert.pem>] -t <message-topic> where,

• -h <hostname>: Specifies the MQTT broker's hostname.

• -p <port>: Specifies the MQTT broker's port number.

• -u <username>: Specifies the username for authentication.

• -P <password>: Specifies the password for authentication.

• --cafile <path_to_ca_cert.pem>: [optional, only use with SSL] Specifies the path to the CA certificate file in PEM format.

• -t <message-topic>: Specifies the MQTT topic you want to subscribe to.

For example, to subscribe to the topic /sensor/envmon/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/#, the mosquitto_sub command is as follows:

Non-secure:

mosquitto_sub -h ext.mqtt.dryad.app -p 31383-u username-P password-t /sensor/envmon/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/#

Secure (uses ISRG Root X1 CA certificate):

mosquitto_sub -h ext.mqtt.dryad.app -p 31393 -u username -P password --cafile isrgrootx1.pem -t /sensor/envmon/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/#

You can find more about the command line options in the mosquitto_sub manual.

Unsubscribe

With mosquitto_sub, the command syntax for unsubscribing from a topic is as follows:

mosquitto_sub -h <hostname> -p <port> -u <username> -P <password> [-–cafile <path_to_ca_cert.pem>]-U <unsub-topic>

where,

• -h <hostname>: Specifies the MQTT broker's hostname.

• -p <port>: Specifies the MQTT broker's port number.

• -u <username>: Specifies the username for authentication.

• -P <password>: Specifies the password for authentication.

• --cafile <path_to_ca_cert.pem>: [optional, only use with SSL] Specifies the path to the CA certificate file in PEM format.

• -U <unsub-topic>: Specifies the MQTT topic you want to unsubscribe from.

For example, to unsubscribe from the topic /sensor/envmon/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/#, the mosquitto_sub command is as follows:

Non-secure:

mosquitto_sub -h ext.mqtt.dryad.app -p 31383 -u username -P password -U /sensor/envmon/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/#

Secure (uses ISRG Root X1 CA certificate):

mosquitto_sub -h ext.mqtt.dryad.app -p 31393 -u username -P password --cafile isrgrootx1.pem -U /sensor/envmon/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/#

You can find more about the command line options in the mosquitto_sub manual.

MQTTx

This guide explains how to use MQTTx as an MQTT client to subscribe to sensor data from Dryad's external MQTT broker. MQTTx provides you a GUI for configuring and connecting to any MQTT broker, allowing you to create subscriptions to receive data.

• Download the MQTTx client and install it on your computer. It is available for Windows, Mac, and Linux, and you can also run it inside a Docker container.

• Start MQTTx.

• Click on the + New Connection button.

• Enter the following information in the New window. Here, we focus only on the basic and minimal parameters needed to create a subscription and connect to Dryad's external MQTT broker. Using other advanced parameters is beyond the scope of this example. You may refer to the MQTTx documentation for more information.

• You can connect to the Dryad's external MQTT broker in two ways:

  • Non-secure

  • Secure

• To connect in a non-secure way, enter/configure the following parameters under the General section:

  • Name: Enter any name to identify your subscription.

  • Host: mqtt:// + ext.mqtt.dryad.app

  • Port: 31383

  • Client ID: Auto generated.

  • Username: Username for your site, provided through 1Password

  • Password: Password for your site, provided through 1Password

  • SSL/TLS: Off

• To connect in a secure way, enter/configure the following parameters under the General section:

  • Name: Enter any name to identify your subscription.

  • Host: mqtts:// + ext.mqtt.dryad.app

  • Port: 31393

  • Client ID: Auto generated.

  • Username: Username for your site, provided through 1Password

  • Password: Password for your site, provided through 1Password

  • SSL/TLS: On

  • SSL Secure: On

• After configuring the required parameters, click on the Connect button.

• Once connected, you will see the following window. Click on the + New Subscription button.

• The New Subscription window appears. In the New Subscription window, enter the topic to subscribe to. The format of the topic is as follows.

  • /sensor/envmon/<site_id>/#

• Click on the Confirm button.

• The sensor data from your site will now be displayed in MQTTx as it arrives at the Dryad cloud/application. Make sure to select JSON from the dropdown menu to view the sensor data in a properly formatted way.

• The image below shows the sensor data under a non-secure connection (Port: 31383).

• The image below shows the sensor data under a secure connection (Port: 31393).

For more information, read MQTTx docs.