FAQ - frequently asked questions PLCcom for Modbus

You have a question relating to PLCcom for Modbus?
Then you are exactly right to be in our FAQ section. We are gradually building up for you here a catalogue with the frequently asked questions of our customers.

If you cannot solve a problem using our FAQ, you have the option in the contact section to personally contact us with your request. We are available to you with pleasure, with our advice and expertise.

Which system components require the PLCcom?

Here is an overview of the recommended system components:

  • Microsoft .NET Framework 4.7.2 (.Net Version) or higher 
  • Microsoft .NET Core 3.1 (.Net Version) or higher 
  • Microsoft .NET Standard 2.1 (.Net Version) or higher 
  • Microsoft .NET 5.0 (.Net Version) or higher 
  • Microsoft .NET Compact Framework 3.5 (CE Version) or
  • Java SDK (openJDK) 1.8 / JRE (openJRE) 8 or newer (Java-Version)


To run the attached program examples you need the following programming tools:

  • Visual Studio 2019 or newer (.Net-Version)
  • Visual Studio 2008 (CE Version)
  • Netbeans 8 or newer (Java)
  • Eclipse Oxigen or newer (Java)

Which files do I need to refer in my software?

To use the .Net / WinCE-component you have to refer to the PLCcomMB.dll.

To use the Java-component you have to refer to the PLCComModBus.jar and jssc.jar.
Best practice: copy the files to your java home dictionary [jdk HOME]/jre/lib/ext or [jre HOME]/lib/ext.

Does PLCcom for Modbus also runs in 32-Bit- and 64-Bit-environments?

Yes, PLCcom runs in 32-Bit- and 64-Bit-environment.

Are OS-API calls necessary to operate PLCcom for Modbus?

The libraries are, depending on the version, to 100% Java or .Net code.
You can embed the driver directly as a link; API calls are not necessary.
It is no problem to use the component in 32- or 64-Bit-environments, as well as across platforms.

Where can I find code examples and the documentation?

In the download package, extensive programming example objects, as well as a HTML documentation are included.

Download current version of documentation:

.Net http://www.plccom.de/help_modbus/Net/help/index.html

Java http://www.plccom.de/help_modbus/Java/javadoc/index.html

What should be considered when using PLCcom in a network?

The network participants must be able to connect with the network. The Connection and ports must not be interrupted by a firewall or similar.

What is the basic principle of the PLCcom license model?

The license model of PLCcom is kept as simple as possible.
All licenses are made available as developer licenses.
The fee-based professional license entitles a developer for industrial/commercial development of individual software (definition see EULA) with the PLCcom component.

Can I use PLCcom commercially free of charge, for example for teaching purposes at a university or for domestic use?

If you need a free license for schools or universities please contact us.

How can I get the licenses?

To get the licenses you have the following possibilities:

  • on our website
  • by sending an email to info@indi-systems.de
  • by phone at +49 421 989703-30
  • by fax to +49 421 989703-39

How is the license within the PLCcom Runtime to install?

You must transfer the submitted license key within your software to the PLCcom entity.

In our company the number of employees who work on a project keeps changing. Therefore, the number of licenses required changes. Is there a possibility for a flat-rate licensing?

Please contact us in this case. We will then create an offer for a company license.

Is the passing of the license to my clients possible?

No, if your customer wants to make a further development of your software, the customer needs an own license.

What type of PLC and devices can I connect with PLCcom?

PLCCom is compatible with all Modbus devices that support the specification of Modbus Organization.

What happens to my data after registration?

The data entered by you will be kept confidential in accordance with the Federal Data Protection Act.
A processing of the data occur only for internal purposes, such as the management of licenses, newsletter etc. A disclosure to third parties is excluded.

What are multiple listeners?

Slave-component whit multiple listeners; that means it is possible to make any numbers of accesses to a Modbus Slave available at the same time e.g. TCP Port502, TCP Port503, UDP Port 502, etc.