MQTT

MQTT (Message Queuing Telemetry Transport) is a lightweight publish/subscribe protocol designed for efficient communication between devices in environments with limited bandwidth or high latency. It is widely used in IoT applications for real-time data exchange between sensors, edge devices, and servers.

DataTalk acts as an MQTT client, subscribing to topics from an external MQTT broker.

Device identification

MQTT devices can be identified in two ways:

ID in payload — the device identifier is part of the message body:

Topic:   sensors
Payload: {"ID": 1, "temperature": 23}

ID in topic — the device identifier is part of the topic path:

Topic:   sensors/1
Payload: {"temperature": 23}

When creating an MQTT connection, specify which method your devices use. DataTalk then uses the unique identifier as the tag address in the Tag Database.

Supported data types

Data type	Description
Buffer	Raw binary data
String	UTF-8 encoded text
Number	32-bit integer
Boolean	True/False
null	Null value

Connection parameters

Parameter	Description
Broker address	Hostname or IP of the MQTT broker. For TLS use mqtts:// prefix, e.g. mqtts://192.168.1.10
Port	Default 1883 (unencrypted) or 8883 (TLS)
Client ID	Unique identifier for this connection on the broker
Username / Password	Credentials if the broker requires authentication
Topic	Topic(s) to subscribe to; supports + (single level) and # (multi-level) wildcards

Tags and UDT

MQTT tags in the Tag Database use the UDT type. To configure log groups, limits, or scaling for MQTT tags, set them first in the UDT section — changes propagate automatically to all tags using that UDT.