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All IoT communication protocols can be implemented and used on different transmission media via software . Data exchange is performed by explicitly calling functions or function blocks as part of the IEC 61131-3 control application.

With the library concept integrated in CODESYS, such protocols can be easily maintained and passed on as products after their implementation.

In the CODESYS Store, you will find the communication library CODESYS IIoT Libraries along with the corresponding application examples that implement different communication protocols (indicated in brackets).

  • MQTT Client (MQTT)
  • Web Client (http, https)
  • AWS IoT Core Client (MQTT)
  • Azure IoT Hub Client (MQTT, https)
  • Mail Service (POP3, SMTP)
  • SNTP Service (SNTP)
  • SNMP Library (SNMP)
  • SMS Service (SMS)

Auxiliary libraries help you simplify the communication even more, such as

  • JSON Utilities
  • XML Utility

For more libraries, also from third-party-suppliers, that implement IIoT protocols or connections, please refer to the CODESYS Store at Communication.

CODESYS does not yet support the protocol you need?

The CODESYS Development System is a powerful and modern programming tool. Use it to implement proprietary or standardized communication protocols yourself. In the free basic library network.library you will find the sub-library CAA NetBaseServices.library, which provides you with important basic services. Products created in this way can also be made available to other users in the CODESYS Store free of charge or for a fee (with complete licensing).

CODESYS does not yet support the protocol you need?

How can you purchase and use IIoT libraries for CODESYS?

  • Use controllers with adequate communication interfaces. Millions of CODESYS-compatible single devices and over 1,000 different device types from more than 500 manufacturers offer you a large range of hardware for your automation projects. CODESYS Inside offers a selection of manufacturers that offer CODESYS-compatible devices. Alternatively, you can use the CODESYS Control SoftPLC systems from the CODESYS Store and install them on standard device platforms. Download CODESYS IIoT Libraries from the CODESYS Store and install the software package in the CODESYS Development System.
    Or you can develop your own protocol libraries, which you can make available to other users in the CODESYS Store. Have experienced specialists advise and support you in architecture design and implementation. Further information at CODESYS User Services.
  • You are a manufacturer of programmable devices: Implement the required communication components of the CODESYS Runtime Toolkit in your devices, as well as the possibility to license libraries per device.


CODESYS offers seamlessly integrated communication protocols for a wide variety of interfaces and requirements.

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OPC Server

Standard Interface to access the IEC 61131-3 process data of a controller via Open Platform Communications.

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Standard Interface for Communication in Smart Factory and Industry 4.0 Systems

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Compact software interface (API) for easy access to the PLC variables in CODESYS controllers from external systems

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Configurator and protocol stack fully integrated in the IEC 61131-3 Development System

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Serial interfaces

Although today almost every industrial controller has an Ethernet connection, serial interfaces are still installed in many industrial devices. This allows, for example, for the connection of appropriately equipped sensors and actuators or extensions.

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Standard Ethernet

How does CODESYS communicate via Ethernet? How can I send and receive data from a CODESYS-compatible PLC via TCP or UDP? How can I realize data exchange from the PLC application?

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Fieldbus systems and Industrial Ethernet

Sensors and actuators/actuators for processing control tasks can be separated from the controller via fieldbus and Ethernet systems with industrial communication protocols.

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Other communication options

If a physical port is available on a controller, communication protocols can usually be implemented simply via software, either as part of the IEC 61131-3 control application or as separate library modules. Data exchange is performed by explicitly calling functions or function blocks as part of the logic control.

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Proprietary communication protocols

CODESYS supports the most common standard communication protocols for data exchange between controllers, such as OPC UA. In addition, Ethernet-based fieldbus systems such as PROFINET or EtherNet/IP™ make it easy to exchange data between controllers by implementing master and slave functions.

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