CODEWITHSUNDEEP
ibm-cloudmqttiotnode-red
William 'Bill' Wentworth
William 'Bill' Wentworth

Reputation: 1787

Do Node-RED applications using Bluemix IoT Foundation require separate topics for devices and applications?

For a Node-RED application, I am using MQTT to talk with the device. Do I need to use two "topics"?:

Alternatively, can both the device and Node-RED application post different information (both publishing and subscribing) to the same topic?

For example: If the device is both publishing temperature data and also subscribing to the same topic to get information from Node-RED in Bluemix, will that cause issues? There are two types of data I want to exchange:

Upvotes: 2

Views: 360

Answers (1)

ValerieLampkin
ValerieLampkin

Reputation: 2626

You should use two different topics.
Applications (such as Node-RED) that connect to the IoT Foundation service publish commands to devices and subscribe to device events.

The device would subscribe to the command topic, and the application (Node-RED) to the event topic.

Your device will be publishing events – such as temperature. So the device should publish that event to a topic in the format iot-2/evt/event_id/fmt/format_string and your Node-RED application will be publishing a command to a different topic.

For example... You could publish temperatures like this:

iot-2/evt/temperature/fmt/json { d: { temp: 25 } } and publish commands to the device like this: iot-2/cmd/sendTemperature/fmt/json

The device would subscribe to the command topic, and the application (Node-RED) to the event topic. Specifically, when you are publishing events, you publish to topic iot-2/evt/event_id/fmt/format_string and devices subscribe to commands by subscribing to topic iot-2/cmd/command_id/fmt/format_string

See the online documentation for MQTT and IoT.

Upvotes: 2

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