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

Access to the PLC Data in the Controller Application

The CODESYS PLCHandler is an easy-to-use software interface (API) for the communication between CODESYS controllers and external client systems. An external client like a visualization or a service panel can access the IEC 61131-3 variables and the online services of the controller using this API.

Functionality of the CODESYS PLCHandler (excerpt)

  • Establishing or terminating a controller connection
  • Reading the variable list of the controller
  • Cyclical reading of variable values from the controller
  • Synchronous exchange of variable values (read/write) with the controller
  • Instantiability for the simultaneous communication with several controllers
  • Automatic reconnection to the controller after connection failure
  • Automatic reconnection after a program download from CODESYS to the controller
  • Transfer of data to and from the controller
  • Callback functions for different events

The CODESYS PLCHandler has been implemented as a C++ class and is delivered in form of a Software Development Kit (SDK). Above that, the PLCHandler also offers a plain C interface and is available as an ActiveX component for Microsoft Windows. Apart from platform-specific files for example for Windows, Linux® or VxWorks® the SDK also contains trial clients in source code for different platforms.


The PLCHandler is purchased by companies who want to establish a connection between an external system and CODESYS.

  • Manufacturers of programmable devices or vendors of third-party systems such as visualizations, operating panels etc.:
    Company license to access CODESYS controllers with the “CODESYS PLCHandler for device manufacturers” from a certain platform
  • System integrators and users for example from the machine or plant building industry: If you want to establish a connection to a third-party system, please contact your system/device supplier or us. 
  • For more information or an offer please contact our sales department under

CODESYS brochures and information material

CODESYS - One software. All applications. Your Automation Solution.
Version: 10/2023
pdf 2 MB
CODESYS - One software. Any field of application. Your automation platform.
Version: 10/2023
pdf 2 MB
Various suppliers present CODESYS-compatible devices and exciting solutions that can be useful for your automation tasks. (Only available in german language.)
Version: 11/2022
pdf 3 MB