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PLCcom for Modbus - Downloads and resources

Here you will find the latest versions of PLCcom for Modbus for .NET and Java, as well as key resources including downloads, documentation, changelogs, data sheets and sample projects.

Evaluation mode: If the licence details – username and serial number – are left blank, the library will run with full functionality for 15 minutes during a debug session – long enough to establish a connection and test functions. This allows you to try out the library before you register.
To ensure you can work without interruption, you can generate a free 14-day trial licence – right here, alongside the relevant download.

.NET Version

PLCcom for Modbus

for comfortable creation of your own Modbus communication applications using .NET

Current version: 9.2.1

Upload date: 11.08.2026

9.2.1

Integrate PLCcom for Modbus directly into your .NET project via NuGet.

<itemgroup>
  <packagereference include="PLCcomModbus" version="{version}" />
</itemgroup>

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Java Version

PLCcom for Modbus

for comfortably creating your own Modbus communication applications using Java

Current version: 9.2.1

Upload date: 11.08.2026

9.2.1

Integrate PLCcom for Modbus directly into your Java project via Maven.

<dependency>
  <groupid>com.indi-an.plccom</groupid>
  <artifactid>plccom-for-modbus</artifactid>
  <version>{version}</version>
</dependency>

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PLCcom Modbus Master Test-App

Free test app

for testing Modbus master connections and initial access to Modbus slaves

Current version: 9.2.1

Upload date: 11.08.2026

PLCcom Modbus Slave Test-App

Free test app

for simulating a Modbus slave and for testing with Modbus master applications

Current version: 9.2.1

Upload date: 11.08.2026

SDK – Informations

EU Compliance (CRA)

Cyber Resilience Act (EU 2024/2847)

Data Sheet

All the functions PLCcom for Modbus can be found here:

Functions:

integrated Modbus Master components
integrated Modbus Slave components
Access via TCP, UDP, RTU or ASCII
Modbus Master: supports function codes 1,2,3,4,5,6,7,8,11,12,15,16,17,22,23,43/MEI13 and self-defined function codes
Modbus Slave: supports function codes 1,2,3,4,5,6,8,15,16,23
Read Coils, Discrete Inputs, Holding Register, Input Register
Write Coils and Holding Register via Modbus Master
Write Coils, Discrete Inputs, Holding Register, Input Register via Modbus Slave
optional 32-Bit Register Modus to plotting 32-Bit-Numbers in a Register (Usually other tool only provide 16Bit-Register)
Combining several read operations into one optimized read call (read collections), the Modbus accesses required for this are reduced to the logical minimum
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.
automatic selection of the Modbus function code for write accesses on request
selectable number coding for reading and writing registers
implemented high-performance access
internal auxiliary and conversion functions for easy reading and writing of certain data types
Read and write operations for following data types (depends on target region)
- Bit
- Byte
- Short
- UShort
- Integer
- UInteger
- Long
- Ulong
- Float
- Double
- PLC_Word
- PLC_DWord
- LWord
- PLC_INT
- PLC_DINT
- PLC_LINT
- 16Bit BCD
- 32Bit BCD
- String
extensive sample programs and simulation software support you in creating your software
and much more

Changelog PLCcom for Modbus

Version 9.1.5

Secure Modbus TCP has been added as a new communication method.
TLS-secured Modbus communication with a preference for TLS 1.3 has been introduced.
TLS 1.2 is supported as a compatibility mode for existing devices.
PKI store updated with custom, trusted, issued and rejected certificates.
Supports the automatic generation of custom SecureTCP certificates.
Standardised certificate verification has been supplemented with Trusted, Issuer and Rejected sections.
Custom certificate validation has been introduced for proprietary trust models.
Role-based SecureTCP authorisation for slave requests has been added.
Certificate events are provided for applications and the Certificate Manager.
Added 64-bit register mode for compatible 64-bit data types.
Byte order processing for 32-bit and 64-bit values has been extended.
Improved validation of invalid data type combinations in register mode.
Waiting time after connection establishment added via DelayAfterConnect.
Telegram logging for ReadCollection has been expanded.
Master and slave test applications for SecureTCP and certificate management have been expanded.
Certificate Manager has been added to the complete sample applications.
Workshops and sample projects have been restructured and revised.
Examples of public workshops prepared for GitHub.
Support has been extended to include the latest target platforms up to .NET 10 and Java 26.
Release build, signing and package creation have been adapted to the current generation of PLCcom.
API and product documentation have been completely revised.
Package description and product documentation updated.
Automatic tests and release checks have been expanded.

Version 8.3.8

Bugfix: If a Modbus slave sends an error code to the master due to a write command, a NullPointer exception was triggered in the response

Version 8.3.6

Bugfix: When using non-optimized ReadRequestCollections, the SlaveId 1 is always transferred
internal adjustments and improvements

Version 8.3.3 ( .Net version only)

Support for .net7 and .net8
Reference upgrade System.Io.Ports to version 8 (.Net version only)
internal adjustments and improvements

Version 8.2.2

Bugfix: Problem writing with Mask Write Register function (FC22)

Version 8.2.1 (.Net version only)

Bugfix: No connection (Modbus Master) under .Net Core 3.1
.Net Core code examples added

Version 8.1.1

Support .Net 6 (only .Net version)
Reference upgrade System.Io.Ports to version 6 (only .Net version)
Support Java version 17 or openJDK17 (Java version only)
Unlocking function codes 65 to 127 for user-defined functions
Bugfix: Possible aborts of TCP connections when using .Net 5
internal adjustments and improvements

Version 7.3.3 (.Net version only)

Bugfix: Problems creating a TCP connection using .Net 5

Version 7.3.2

Optimization of the timeout behavior in the event of connection interruptions
Bugfix: Problems that may occur when TCP/IP packets are transmitted in split form
various internal adjustments

Version 7.2.6 (.Net version only)

Reference upgrade System.Io.Ports to version 5

Version 7.2.5

Fix problem when using a non-optimized ReadCollection

Version 7.2.1

Fix problem possibly high memory usage Modbus Slave

Version 7.1.1

Support of the .Net 5.0 framework
JRE/JDK at least version 8 or higher
Fix problem fast simultaneous TCP request over multiple ports may cause problems and disconnections
Fix problem possible connection aborts with asynchronous TCP transmission
Nuget package available
Framework Version mindestes 4.2
internal improvements and revisions

Version 6.6.1

Definition of the minimum period in milliseconds between two characters for RTU master instances
Improvement of the TCP / IP connection stability

Version 6.5.1

Specification of the slave ID now possible up to 255, before max. 247
internal optimizations

Version 6.4.1

get STRING datatype with byte order
.Net version, new data type SByte (signed byte)
Java version, new data type UByte (unsigned byte)
Bugfix: Optimized internal speed

Version 6.3.1

Bugfix: When writing individual coils, the following coil could also be written under certain circumstances

Version 6.2.1 (Java version only)

Extension of the enum eFlowcontrol by the members RTSCTS, XONXOFF and RTSCTS_XONXOFF, in order to be able to transfer the handshake more comfortably when using a serail port

Version 6.1.2

new Communication type RTU_over_TCP
(.Net only) 'Readtimeout' property is deprecated, replaced by 'OperationTimeout'.
(.Net only) property 'Connecttimeout' is deprecated, replaced by 'ConnectTimeout' (misspelling)
(.Net only) CRC / LCR check can be enabled and disabled with the property 'CRCCheckEnabled
(Java only) function getReadtimeout() is deprecated, please use function getOperationTimeout() instead
(Java only) method setReadtimeout() is deprecated, please use method setOperationTimeout() instead
(Java only) function getConnecttimeout () is deprecated because of misspelling, please use function getConnectTimeout () instead
(Java only) method setConnecttimeout () is deprecated because of misspelling, please use method setConnectTimeout () instead
(Java only) CRC / LCR check can be switched off on request for the Modbus master with new method/function boolean getCRCCheckEnabled() and setCRCCheckEnabled(boolean value)