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Today, almost every industrial controller has an Ethernet connection. It is usually used for programming the device and exchanging data with other systems. The physical interface can be used with different protocols.

For communication with I/O systems, motors, or intelligent units of the control architecture, Industrial Ethernet protocols are commonly used. For more information, please click here.

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Ethernet with TCP/IP is used in CODESYS not only for programming, but also for communication with CODESYS Visualizations, e.g. with CODESYS HMI or CODESYS WebVisu.

From the IEC 61131-3 logic application, users can also exchange dedicated data. The free network.library is based on the library CAA Net Base Services and is included in the scope of delivery of the CODESYS Development System. This library provides a convenient interface for socket communication from the controller to other systems via TCP/IP and UDP.

The functions of the free RPC.library can also be used to address or release the client/server procedures on the controller ("Remote Procedure Calls").

How can you use Ethernet in CODESYS?

You are a system integrator or a user in the machine/plant construction sector or the like:

  • Program CODESYS-compatible controllers or standard device platforms that are equipped with integrated Ethernet interfaces.
  • Connect additional visualization devices, e.g. operating panels equipped with CODESYS HMI or HTML5 browsers that display the CODESYS WebVisu.
  • Send and receive controller data from the IEC 61131-3 logic application via the available function blocks of the network.library.

You are a manufacturer of programmable devices:

  • Implement in your devices the required communication components of the CODESYS Runtime Toolkit, 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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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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IIoT libraries

All IoT communication protocols can be implemented and used on different transmission media via software.

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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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