MQTT

The gateway can publish sensor data to your own MQTT broker, and subscribe to the same topic for commands. It acts as an MQTT client and works with any broker from MQTT 3.1.1 up to MQTT 5.

Repeater networks

In a repeater network, subordinate gateways send their MQTT data to the Main gateway, which is where the broker connection is configured.

Unlike Modbus and OPC UA, MQTT is a push integration: the gateway publishes whenever a sensor updates its data — on its sensor update interval, or whenever a waveform is taken because of an alarm or an on-demand request.

Settings

Configured in the Gateway Admin Console:

Setting	Notes
Protocol	mqtt://, mqtts://, ws:// or wss://, depending on what your broker supports
MQTT server	Hostname or IP of your broker
Port	The port your broker listens on
Username	Optional
Password	Optional
Publish Topic	Where the gateway publishes data and subscribes for commands
Publish QoS	Quality of Service tag. When in doubt, use 0
Append Gateway and serial number as subtopics	Splits the stream per gateway and per sensor
Publish waveforms	See the warning below
Allow Gateway management through MQTT	See the warning below

Waveforms are large

Each complete time waveform is roughly 160 kB, and needs post-processing to render an FFT. Leave Publish waveforms off unless you are actually going to consume them — on a busy site it will dominate your broker traffic.

Gateway management over MQTT

Allow Gateway management through MQTT lets any client connected to the same broker change all gateway and sensor settings. Only enable it on a broker you control and whose clients you trust.

This setting is what unlocks the Management API over MQTT. Leave it off if you only want telemetry.

Pressing Save stores the settings and restarts the gateway. After it restarts it connects to the broker and shows the connection state in the MQTT section at the top of the console. Reset reverts to the previous values.

Message fields

Every published JSON message carries these fields:

Field	Description
dataType	"collection" for vibration time waveforms, "stateupdate" for everything else — including a vibration sensor’s own internal RMS measurement
type	Sensor type
phantomCode	Sensor serial number
gwSerial	Gateway serial number
timestamp	Seconds since 1970, when the measurement was taken
battery	Battery level in volts
batteryType	1 = 1/6D, 2 = AAA, 3 = CR2032, 4 = CR2477
temperature	Sensor internal temperature in °C
version	Firmware version
rssi	Sensor signal strength

Note

Note that timestamp here is seconds since the epoch, while the Management API reports its timestamps in milliseconds. See Data conventions.

Beyond telemetry

Everything above describes the gateway publishing sensor data. The same MQTT connection can also carry the Management API, which lets you read the gateway’s full state and send it commands.

Coexistence

MQTT runs at the same time as any other protocol the gateway supports, including EI Analytic, EI Monitor, OPC UA and Modbus.