The Hobson MQTT plugin allows external devices (such as sensors) to connect to Hobson via MQTT for sending and/or receiving of data.
When the plugin is installed, Hobson creates a local MQTT server that devices can connect to anonymously. The anonymous connection is used by a device to obtain a device passport from Hobson. This passport allows the device to re-connect securely to Hobson's MQTT server and participate as a normal device within the Hobson system.
The process a device uses to obtain device passport information from Hobson is referred to as bootstrapping.
When a device with no bootstrap information is powered on, it should immediately begin the bootstrapping process.
The bootstrapping process should ideally only performed once. However, there may be circumstances where a device has to go through the process again (for example, if the device is factory reset).
Below is an outline of the steps involved in the bootstrapping process:
The below diagram visually illustrates a successful bootstrapping sequence:
Hobson is always listening on the bootstrap request topic for bootstrap request messages. The topic is of the form:
When a bootstrap request message is received, Hobson will confirm the validity of the request and issue a bootstrap response message (see the Messages section below).
Hobson will publish its bootstrap response message to the bootstrap response topic. The topic is of the form:
where deviceId and nonce are values taken from the bootstrap request message (see the Messages section below).
Note: The only topics that the anonymous MQTT user can subscribe to are bootstrap topics.
There are a few reasons why a device's bootstrapping attempt might fail:
A successfully bootstrapped device will have stored the bootstrap data included in the bootstrap response message. That data is comprised of:
When a successfully bootstrapped device is initialized, it should automatically connect to its identified Hobson MQTT server using its unique credentials. Once connected, it can listen for command messages or send data messages using the appropriate topics.
There may be cases where a Hobson user revokes a device that was previously bootstrapped using the web console or REST API. This may happen, for example, if the device was somehow compromised.
When a device is revoked, its unique MQTT credentials become invalid and any attempt to connect to the MQTT server using them will fail. A device should detect this situation and automatically revert itself to an un-bootstrapped state and begin the bootstrap process again.
When the Hobson Hub is running in secure mode, all MQTT traffic uses SSL/TLS channel encryption and the adding of the device ID to Hobson prior to device bootstrapping is required.
When the Hobson Hub is running in insecure mode (e.g. on a secure network or for testing purposes), MQTT traffic uses no channel encryption and Hobson will always successfully respond to a bootstrap request message.
|deviceId||String||No||The device's unique ID|
|nonce||String||No||A device-generated nonce that will be used as part of the bootstrap response topic (as with any nonce, it should not be re-used)|
|name||String||Yes||The device's name|
|data||Object||Yes||The initial values for all the device's variables|
JSON example (a device that reports temperature and humidity data):
"name": "Sensor 1",
|error||String||A description of the error that occurred (if this is present, the rest of the fields will not be).|
|id||String||The username that should be used for subsequent connections to the MQTT server|
|secret||String||The password that should be used for subsequent connections to the MQTT server|
The topics the sensor should publish and subscribe to
the variable value as a string
JSON example (temperature and humidity data):