MQTT Publish

The MQTT Publish Action Component allows you to publish messages to topics within an MQTT PubSub system.

Output Payload	Explanation
cv.Payload	Outputs the output payload of the previous component as is. (Pass through)

Component Properties

Name	Required	Description
Topic	True	MQTT Topic
ClientId	True	MQTT ClientID
QoS	True	QoS value
Retain	True	Retain flag
Timeout	True	Timeout (ms)
MQTT Connection	False	MQTT Connection Settings from the Base Property Profile
URL	True	URL, note, leave the protocol out for unencrypted connections (e.g. test.mosquitto.org) but add ssl:// for encrypted connections
Port	True	Port
Username	False	Username
Password	False	Password
Certificate	False	Certificate
Private Key	False	Private Key
Private Key Passphrase	False	Private Key Passphrase
Root CA	False	Root CA

test.mosquitto.org Example

You can easily test the MQTT function by using the free public "test broker provided by mosquito.org":http://test.mosquitto.org. A sample setup could be that you use the free "MQTTX":https://mqttx.app/ client alongside with Gravio using the following details:

Topic	testtopic/gravio
Client ID	Choose something Unique for Gravio and something different for MQTTX
QoS	0
Timeout	60000
URL	test.mosquitto.org
Port	1883
Username	_blank_
Password	_blank_
Certificate	_blank_
Private Key	_blank_
Private Key Passphrase	_blank_
Root CA	_blank_

Then set the contents to cv.Payload = {"msg": "your test message"}

Triggering the action from Gravio Studio:

You should see something similar to the following in MQTTX:

Note: Ensure that both, MQTTX and Gravio have different Client IDs as the MQTT broker will disconnect the clients if they share the same ID.

Google Cloud MQTT Example

Here is an example of how to publish messages to a Google Cloud MQTT System:

Navigate to your Google Cloud console and create a project:

Navigate to Google Cloud Platform IoT Core

Enable the Google IoT Core API.

Create a Device Registry

Enter the name of your registry, select the region and add the topics (here events and states for example):

Click on "Add Device" in this screen:

And you will see:

Create a certificate that you can paste into the field by entering this command in your command line:

openssl req -x509 -newkey rsa:2048 -keyout rsa_private.pem -nodes -out rsa_cert.pem -subj "/CN=unused"

This will create a file rsa_private.pem and a file called rsa_cert.pem

Copy the contents of the rsa_cert.pem file into the window:

We're now ready to take on messages from Gravio.

Note: The MQTT Publish component will take the variables as payload and make one MQTT publish per variable. And if you use JSON or CSV the variable name will be the key/column.

Typically you can use the CreateRecord component to inject a variable into the MQTTPublish component.

To see how to retrieve MQTT messages, please refer to the "MQTT subscription section"MQTT Configuration of this documentation.