MQTT Client MQTT Client

Simply connect your systems to MQTT

The MQTT protocol (What is MQTT?) 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 UASAPSQL DatabasesEmailREST, 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.

See also our Step by Step tutorials to connect the leading IoT platforms via MQTT:
Connect to the Azure IoT Hub with the MQTT Client
Connect the AWS IoT Cloud via MQTT
Connect the IBM Watson Platform via MQTT
Connecting Siemens MindSphere IoT via MQTT

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Example for an OPC to MQTT Transfer

Data transfer OPC to MQTT

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Connecting Systems

What's Transfer, Trigger and Browsing?

Transfer Objects

The MQTT Client Transfer object allows you to send messages as a publisher. The configuration of the broker is done in the instance of the plug-in. The Topic and Payload fields are transferred to the transfer object.
When the transfer is completed, the data is sent to the broker and thus transferred to the subscribers.
The XPath or JPath plug-ins can be used very well to structure the data in the payload.


The MQTT Client Plug-in provides an MQTT trigger to activate connections.

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


The browsing of topics is not provided in MQTT protocol. For this reason, the MQTT Client Plug-in does not offer browsing.

MQTT Client 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 the 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 point of view of OPC Router results from the plug-ins of 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 (manual for the AWS IoT Cloud connection with MQTT), Microsoft Azure (manual for the connection of Azure IoT Hub with MQTT), IBM Watson, ThingWorx.

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 predestined MQTT data sources. With the OPC Router, data from these data sources can be received via a broker and transferred to processing systems such as SQL servers, 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 OPC to MQTT Transfer

Data collected by an OPC server with an OPC UA Client Plug-in is converted into a user-defined JSON string via JPath Plug-in and sent to the MQTT Broker. The Mosquitto Broker was used for the test.

MQTT to SQL Transfer

Example of an MQTT to SQL Transfer

Data is received from a broker via MQTT client plug-in. The reception activates the trigger. The trigger makes payload available and data is written directly to an SQL table via the MS SQL Server plug-in.

Here you will find further information about OPC Router and Plug-ins.

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