What Is MQTT And Which Teltonika Devices Support It

What is MQTT?

MQTT (Message Queuing Telemetry Transport) is a lightweight publish-subscribe messaging protocol built on top of TCP/IP. It is an ISO and OASIS standard (ISO/IEC 20922) and the dominant communication protocol for industrial IoT, machine-to-machine telemetry, and cloud-connected sensor networks. According to the Eclipse Foundation’s 2024 IoT and Embedded Developer Survey, MQTT is the preferred IIoT communication protocol with 56% adoption across the industry.

The protocol was created in 1999 by Andy Stanford-Clark at IBM and Arlen Nipper at Eurotech. Its first application was monitoring crude oil pipelines via satellite link on the SCADA system used by Conoco Phillips. The requirement at the time was a protocol that consumed minimal bandwidth, used little power, and worked reliably over expensive satellite connections with high latency. Those same properties make MQTT the right choice for industrial cellular deployments today.

How MQTT Works

MQTT uses a publish-subscribe model, which is fundamentally different from the request-response model used by HTTP. There are three roles in an MQTT system: publishers, subscribers, and a broker.

A practical example: a temperature sensor on a water treatment plant publishes a reading every 30 seconds to the topic plant/site-a/tank-1/temp. The SCADA server in the control room subscribes to that topic. The broker handles delivery. The sensor never connects directly to the SCADA server. If the network drops temporarily, messages queue at the broker depending on the Quality of Service level selected.

Quality of Service Levels

MQTT defines three QoS levels that control message delivery guarantees.

Why MQTT Outperforms HTTP for IoT Telemetry

HTTP is a request-response protocol. Every data point requires a full request and response cycle, including headers, connection setup, and teardown. An HTTP request can add 2 KB of overhead to a message that contains only 10 bytes of sensor data. MQTT headers are a fixed 2 bytes. For a device sending a reading every 10 seconds over a cellular link with a metered SIM, that difference adds up significantly over time.

MQTT also maintains a persistent connection between device and broker. This reduces reconnection overhead and allows the broker to push commands back to a device without polling. HTTP has no equivalent push mechanism without long-polling or WebSocket extensions.

Why MQTT is the Standard for Industrial IoT

Industrial IoT deployments share common constraints: remote locations, limited bandwidth, variable cellular signal, legacy serial devices, and a requirement that no data is lost. MQTT was built for exactly these conditions.

Key reasons MQTT dominates industrial deployments:

• Low bandwidth consumption. Small fixed headers and compact payloads suit metered cellular SIM cards and narrow-band connections.
• Persistent sessions. If a device loses connectivity, the broker stores messages until the device reconnects (subject to QoS level). No data is silently discarded.
• Decoupled architecture. Publishers and subscribers have no direct connection. Adding a new monitoring application means subscribing to an existing topic, with no changes to the field device.
• Bidirectional communication. A device can publish sensor data and simultaneously subscribe to a control topic, receiving commands from a cloud platform or SCADA system.
• TLS encryption support. MQTT over TLS is the standard for secure cloud connectivity, supported by all major cloud IoT platforms.
• Wide platform support. AWS IoT Core, Azure IoT Hub, Google Cloud IoT, and HiveMQ all use MQTT as their primary device connection protocol.

How Teltonika Routers Implement MQTT

Every Teltonika router and gateway running RutOS includes MQTT support as a standard feature. There are no licence fees or separate modules to purchase. The implementation is built on the open-source Mosquitto broker, which is the most widely deployed MQTT broker in production IoT systems.

A Teltonika router running RutOS can operate in three distinct MQTT roles simultaneously.

The Data to Server Function

RutOS includes a Data to Server service that handles the outbound publishing pipeline. This service collects data from multiple local sources – Modbus readings, I/O states, Bluetooth scanner results, GPS position, and router system metrics – and formats them as JSON or custom text payloads before publishing to a configured MQTT broker. The destination can be the router’s own local broker, AWS IoT Core, Azure IoT Hub, or any custom MQTT endpoint.

Configuration is done through the WebUI with no command-line access required. Teltonika also provides ready-made configuration guides for connecting to AWS IoT, Azure IoT Hub, and other major platforms via the Teltonika wiki.

Why Routers Without Serial Ports Still Support MQTT

A common assumption is that MQTT only matters for routers with RS232 or RS485 ports, because those ports are used to connect serial industrial devices. This is not the case. MQTT support in RutOS is independent of the physical interfaces on the router.

A router with Ethernet ports only, such as the RUT200 or RUTX10, supports MQTT in the following ways:

• Router telemetry publishing. Every RutOS device can publish its own signal metrics, uptime, WAN status, and data usage to any MQTT broker. This is useful for network operations monitoring without any attached sensors.
• Local MQTT broker for LAN devices. Any sensor, PLC, or edge device on the router’s LAN that speaks MQTT can publish to the router’s built-in Mosquitto broker. The router then bridges those messages to a cloud broker over the cellular WAN. This turns the router into a local MQTT concentrator for an entire site.
• Modbus TCP gateway to MQTT. If a Modbus TCP device is connected via Ethernet, the router can poll it as a Modbus TCP master and forward the data via MQTT. Modbus TCP is the IP-based variant of the Modbus protocol and requires no serial port.

Routers that additionally have RS232 or RS485 ports, such as the RUT906, RUT956, TRB142, and TRB145, extend this further. They connect directly to legacy Modbus RTU devices over serial and translate those readings to MQTT in the same pipeline. The Modbus RTU serial gateway function converts RS485 and RS232-connected slave devices into Modbus TCP internally, making their data available to the MQTT gateway in the same way as Ethernet-connected devices.

Connecting Teltonika Routers to Cloud Platforms via MQTT

Teltonika routers connect directly to major cloud IoT platforms using MQTT with TLS. No intermediary server is required. The router handles certificate-based authentication and encrypted transport to the cloud endpoint.

For AWS IoT Core, the router is configured as a thing with an X.509 certificate and private key. Data published via MQTT appears in the AWS IoT rules engine, where it can be routed to DynamoDB, S3, Lambda functions, or Grafana dashboards. Setup is documented in full on the Teltonika wiki.

Azure IoT Hub uses a similar certificate-based approach. The router acts as an IoT device registered in the hub. Data published over MQTT is received by Azure IoT Hub and can be routed to Azure Stream Analytics, Azure Time Series Insights, or Power BI for dashboarding.

For deployments using a fixed IP SIM card, the router can also connect to a self-hosted MQTT broker on a private server, using a static address for the broker endpoint. This suits organisations that want to keep data on-premises rather than in a public cloud. See our fixed IP SIM cards for details on the SIM connectivity required for this architecture.

MQTT Use Cases on Teltonika Routers

Remote Substation and Utility Monitoring

Electricity substations, water pumping stations, and gas pressure reduction stations all contain instrumentation that generates telemetry continuously. A Teltonika router with RS485 reads Modbus RTU registers from meters, pressure sensors, and flow monitors, then publishes the data to an MQTT broker connected to a SCADA system. Operators see live readings from every site on one dashboard. Alerts publish to a separate topic the moment a reading exceeds a threshold.

EV Charge Point Monitoring

OCPP-based charge point management systems often use MQTT for the connection between the charger and the cloud backend. A Teltonika router provides the cellular backhaul for charge points at sites without fixed broadband. The router’s dual SIM support and automatic failover ensure the MQTT connection stays up even if one network drops.

Fleet and Asset Telemetry

Vehicles and mobile assets publish GPS position, engine data, and driver behaviour scores to an MQTT broker via the cellular-connected router. The broker routes position data to a fleet management platform and engine data to a maintenance system simultaneously, with each system subscribing only to the topics it needs. No data is duplicated and no changes are needed at the vehicle if a new subscriber is added.

Industrial Machine Monitoring

Manufacturing plant equipment – CNC machines, compressors, conveyors – exposes operational data via Modbus TCP or Modbus RTU. A Teltonika gateway reads those registers and publishes them via MQTT to an on-premise broker connected to a historian database. Maintenance teams subscribe to machine health topics and receive alerts when vibration, temperature, or cycle counts exceed limits.

Environmental and Agricultural Monitoring

Remote weather stations, soil sensors, and water quality instruments publish readings via MQTT at low frequency. The lightweight protocol suits battery-powered devices on narrow cellular connections. QoS 1 ensures readings are delivered even if the cellular connection is interrupted during a reading cycle.

Building Management Systems

BMS controllers for HVAC, lighting, and access control often support MQTT as an output protocol alongside BACnet and Modbus. A Teltonika router acts as the broker and cellular gateway in a single unit, collecting data from BMS sensors across a site and forwarding it to a cloud-based building analytics platform.

Teltonika Devices That Support MQTT

All Teltonika devices running RutOS support MQTT as standard. The table below covers the full current range, all of which are available from routerstore.com. Call us on 0300 124 6181 to discuss which device best fits your MQTT architecture.

All models support: MQTT broker, MQTT publisher (router telemetry), and Modbus TCP to MQTT gateway. Models with RS232 or RS485 additionally support Modbus RTU serial to MQTT.

Related Products and Further Reading

For RS485 Modbus RTU to MQTT deployments, the Teltonika TRB series IoT gateways are the compact choice. For higher bandwidth sites needing both MQTT and VPN, the Teltonika 4G router range covers RUT and RUTX series. 5G sites can deploy the Teltonika 5G router range for MQTT over high-throughput cellular. For RUTC series deployments requiring Docker-hosted MQTT brokers or custom processing pipelines, see our pages on the RUTC40 and RUTC41. For SIM connectivity, see the IoT SIM connectivity hub.