External clients can send commands to devices by either:

1. writing into device public properties with publish attribute always or changed directly;

2. invoking public methods that writes into properties with publish attribute always or changed indiretcly.

When a public property is written with an API key other than the device key, the written value is automatically sent to the device via MQTT given that property publish attribute is set other than never.

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Attention

If the device is not connected to the broker at the time of writing, the package gets lost. To prevent that happens different QoS levels must be used or a custom feedback mechanism is recommended.

Make sure that property publish attribute is set to always or changed if you want to send the property value to the device.

Note that in some cases you might want to store property values only on the server-side. In such cases set property publish type to never.

Important MQTT Topics

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Property Names in Topics

Property names must be always given in lowercase within the topic paths.

Sending Commands over MQTT

MQTT provides a stateful and bi-directional connection to devices. The same connection can be used both for writing and receiving data to/from the platform.

In order to receive commands from the platform a device should do the following:

1. It should connect to one of the MQTT endpoints using its device id as the client id, device key id as the username and device key secret as the password.

2. Once connected, it should subscribe to connio/data/in/devices/{id}/properties/#or connio/data/in/devices/{id}/properties/{name} and listen for incoming data and commands.