80 lines
3.3 KiB
Markdown
80 lines
3.3 KiB
Markdown
MQTT Client Example
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===================
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The MQTT client can be used to:
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* Publish sensor readings to an MQTT broker.
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* Subscribe to a topic and receive commands from an MQTT broker
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The demo will give some visual feedback with a LED (configurable):
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* Very fast blinking: Searching for a network
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* Fast blinking: Connecting to broker
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* Slow, long blinking: Sending a publish message
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This example is known to work with all platforms that support the new button
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API.
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This example can operate in two modes: A default mode to be used with the
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mosquitto MQTT broker and a second mode to be used with the IBM Watson IoT
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platform.
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To enable Watson mode, define `MQTT_CLIENT_CONF_WITH_IBM_WATSON` as 1 in the
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example's `project-conf.h`.
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Publishing
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----------
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By default the example will attempt to publish readings to an MQTT broker
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running on the IPv6 address specified as `MQTT_CLIENT_CONF_BROKER_IP_ADDR` in
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`project-conf.h`. This functionality was tested successfully with
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[mosquitto](http://mosquitto.org/). This define will be ignored in IBM Watson
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mode.
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The publish messages include sensor readings but also some other information,
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such as device uptime in seconds and a message sequence number. The demo will
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publish to topic `iot-2/evt/status/fmt/json`. The device will connect using
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client-id `d:<org-id>:mqtt-client:<device-id>`, where `<device-id>` gets
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constructed from the device's IEEE address. `<org-id>` can be controlled
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through the `MQTT_CLIENT_CONF_ORG_ID` define.
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Subscribing
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-----------
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You can also subscribe to topics and receive commands, but this will only
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work if you use "Org ID" != 'quickstart'. To achieve this, you will need to
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change `MQTT_CLIENT_CONF_ORG_ID` in `project-conf.h`. In this scenario, the
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device will subscribe to:
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`iot-2/cmd/+/fmt/json`
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You can then use this to toggle LEDs. To do this, you can for example
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use mosquitto client to publish to `iot-2/cmd/leds/fmt/json`. So, to change
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the state of an LED, you would do this:
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`mosquitto_pub -h <broker IP> -m "1" -t iot-2/cmd/leds/fmt/json`
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Where `broker IP` should be replaced with the IP address of your mosquitto
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broker (the one where you device has subscribed). Replace `-m "1'` with `-m "0"`
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to turn the LED back off.
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Bear in mind that, even though the topic suggests that messages are of json
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format, they are in fact not. This was done in order to avoid linking a json
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parser into the firmware. This comment only applies to parsing incoming
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messages, outgoing publish messages use proper json payload.
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IBM Quickstart Service
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----------------------
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It is also possible to publish to IBM's quickstart service. To do so, you need
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to enable this mode by setting `MQTT_CLIENT_CONF_WITH_IBM_WATSON` to 1 in
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`project-conf.h`.
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The device will then try to connect to IBM's quickstart over NAT64, so you will
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need a NAT64 gateway in your network to make this work. A guide on how to
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setup NAT64 is out of scope here, but you can find one in the
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[Contiki-NG wiki](https://github.com/contiki-ng/contiki-ng/wiki/NAT64-for-Contiki%E2%80%90NG).
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If you want to use IBM's cloud service with a registered device, you will need
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to set `MQTT_CLIENT_CONF_ORG_ID` and then also to provide the 'Auth Token'
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(`MQTT_CLIENT_CONF_AUTH_TOKEN`), which acts as a 'password'. You will also
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need to configure your Organisation / Registered device on Watson such that
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TLS is optional.
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Note: The token will be transported in cleartext.
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