MQTT Client

Simply connect your systems to MQTT

The MQTT protocol is a widely used protocol in the IoT (Internet of Things). MQTT works according to the publisher/subscriber principle and operates via a central broker. This means that senders and recipients have no direct connection, but the data sources report their data via a publish and all recipients interested in certain messages (identified by the “topic”) receive the data because they have registered as subscribers.
In the industrial environment there are many sensors as publishers and superimposed systems as subscribers. In contrast to OPC UA, the data content of messages remains unspecified and is specified by the publisher. In OPC UA, on the other hand, the structures of the communicated data are predefined.

With the OPC Router as MQTT subscriber you can use data from MQTT Publisher and pass it on to any system via the other plug-ins (OPC UA, SAP, SQL Databases, EmailREST, etc.). As a MQTT publisher the OPC Router can send data from non-MQTT-enabled sources to a broker to provide any MQTT subscriber with data.

New: Step by Step tutorial to connect to the Azure IoT Hub with the MQTT Client Plug-in. Also available as tutorial to connect the AWS IoT Cloud.

Example for an OPC to MQTT Transfer


Achieve More with Combined Systems

Use MQTT to send or receive valuable data to/from MQTT-enabled systems. The MQTT plug-in paves the way to the IoT world.

Industry 4.0 via MQTT

The OPC Router allows you to network your systems graphically. Numerous plug-ins make it the data hub in the industrial environment.

Simple configuration, sophisticated monitoring and robustness distinguish it.

About the OPC Router

The OPC Router offers a visual configuration interface for successful cross-linking of your systems. A high variety of plug-ins turns the OPC Router into a powerful datahub for industrial applications.

Easy configuration, sophisticated monitoring and robustness are main distinguishing features of the OPC Router.

Linking Systems

That’s how easy it is.

Transfer Objects

The MQTT Transfer object allows you to send messages as a publisher. The configuration of the broker is done by instance of the plug-in. The fields Topic and Payload are transferred to the transfer object.
The data is sent to the broker when the transfer is executed and thus transferred to the subscribers.

The plug-ins XPath or JPath can be used very well for structuring the data in the payload.

Trigger Functions

The MQTT plug-in provides an MQTT trigger to trigger connections.

The MQTT trigger is a subscriber for a specific topic (wildcard possible) on a broker. If a message is received, the trigger makes the topic and the payload available in the connection.


Browsing of topics is not provided in the MQTT protocol. For this reason, the plug-in does not offer browsing.

MQTT Plug-in Application-Examples

IoT and Cloud Connection

The IoT lives from intelligent “things” on the one hand, but also from the comprehensive networking of things on the other. This is achieved by the Cloud and IoT platforms. Most of these platforms have the IoT protocol MQTT as one of their primary interfaces. The data to the digital twins of things is exchanged with real things via MQTT. The OPC router with its MQTT client plug-in can serve as a communication partner for these platforms and thus send data from the real world into the platform, but also the way out of the cloud back to the things is possible. What can be regarded as a “thing” from the OPC router’s point of view results from the plug-ins of the OPC router. By combining each of its plug-ins with the MQTT client plug-in, printers, SQL servers, SAP systems and many more can be integrated into the respective IoT platform. Common IoT platforms are for example Amazon AWS IoT (example for the AWS IoT Cloud connection with the OPC Router), Microsoft Azure, IBM Watson, ThingWorks.

MQTT Client
MS SQL Server

Data acquisition from sensors and devices

The MQTT protocol has been specifically designed for low bandwidth devices and networks. Therefore, small and low-power devices and sensors are ideal MQTT data sources. With the OPC Router, the data from these data sources can be received via a broker and then transferred to processing systems such as SQL Server, SAP systems, printers, and others (see plug-ins). Since the MQTT data traffic is bidirectional, data can also be sent to the devices and sensors in this way to make settings or trigger actions.

Example for an OPC to MQTT Transfer

Data collected from an OPC Server via the OPC UA Client Plug-in is converted into a custom JSON string using the JPath Plug-in and sent to the MQTT Broker. The Mosquitto Broker was used for the test.

OPC UA to MQTT Connection

More Plug-ins

How do Transfer Objects, Triggers and Browsing work?

The OPC Router establishes connections between systems that address core functions of the OPC Router.

Functions of the respective plug-ins may vary, due to the different nature of each connected system.

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Transfer Objects

Sources and Destinations

Transfer objects are the sources and destinations inside the OPC Router. They contain data fields with read and write functions. Depending on the respective interconnected system, the possible configuration scope of sources and destinations may vary.

Homegeinity on the Outside – Heterogeinity on the Inside

Inside the OPC Router configuration, the transfer object abstracts the respective system of any connected system into a simple data input and data output block. Thus, the functions can be treated in the same way although each connected system has very individual features.

Trigger Functions

Prompting Connections

Triggers determine execution time of data connections. Various triggers can be used for these connections, independent of transfer object type. Within each connection, several triggers can be used together via AND/OR-connections. Triggers can also be useful as data sources if the prompting event is combined with data reception.


Searching and Finding Data Fields

Easy browsing also makes data field configuration easy when establishing transfer objects in order to establish the respective interface connection. The browsing mechanisms may vary, depending on the system and its available plug-in.

Reading out Structures

Many plug-ins that are available for the OPC Router offer easy search and selection tools for quick identification of respective data fields without the need for specific knowledge about inherent subsystems. The user can easily browse through the data. Data source structures may vary according to the specification of each respective plug-in.