Manually send MQTT messages
If you're not using Connhex Edge, you'll need to manually exchange data with your Connhex instance - both sending messages and receiving commands. This section describes how to do so with MQTT: all the following steps must be implemented in the physical device's firmware.
You can only connect devices which have already been registered (i.e. provisioned) in Connhex. To read more on how you can provision devices, see here.
Initialization: configuration download
This paragraph assumes the device already has its init_id and init_key. In case of more complex setups, a key exchange will have to happen before the device can communicate: read more here and here.
The first step is to retrieve the device config: make sure you're including the init_key as authorization header. The response includes all the parameters needed to connect via MQTT:
| Parameter | Description |
|---|---|
url | Cloud IoT endpoint URL |
connhex_id | Username |
connhex_key | Password |
connhex_channels | MQTT topics. More on this below. |
client_cert | Client certificate |
client_key | Private client key |
ca_cert | Server certificate |
ca_chain | Certificates chain, also containing authorities for domain verification |
MQTT topics
MQTT topics associated with the device follow this format:
channels/<channel_id>/messages/events/<subtopic_id>
where <channel_id> corresponds to one of the IDs contained in the connhex_channels object from the response and <subtopic_id> can be optionally used to segment data according to any policy. For example, when using the Connhex Message Policy with the following channels:
"connhex_channels": [
{
"id": "4ab1d46b-f6f0-4c24-8598-515945071ea7",
"name": "control channel",
"metadata": {
"type": "control"
}
},
{
"id": "54f12aea-e632-4bcd-a164-c2e73dce964a",
"name": "event channel",
"metadata": {
"type": "event"
}
}
]
data can be sent on any of the following: channels/54f12aea-e632-4bcd-a164-c2e73dce964a/messages/events/<infos|params|data>
Ensure you are using MQTT version 3.1.1 or 3.1 for proper compatibility.
Sending data and receiving commands
Your device should now be able to publish data and subscribe to receive commands: make sure you're using one of the supported message formats.