Modbus Organization

Modbus Technical Resources

• Modbus Specifications
  Download the current versions of Modbus specifications and implementation guides.
• Modbus TCP Toolkit
  Learn about the valuable resources available on the Modbus Organization Modbus-TCP Toolkit, free to corporate members and also available to purchase.
• Modbus Conformance Test Program
  Read about the Modbus Conformance Test Program, through which suppliers of Modbus devices can establish their conformance with Modbus specifications.

White Papers

• No White Papers available at present.

Offsite Links

The following links to third party sites will let you leave this site. The linked sites are not under the control of the Modbus Organization and we are not responsible for the contents of any linked site or any link contained in a linked site, or any changes or updates to such sites. We provide these links to you as a convenience only, and the inclusion of any link does not imply endorsement of the site by the Modbus Organization or imply approval of any content, recommendation or application information found on that site. So there.

• ModLink
  ModLink is a set of native VCL components that allows you to integrate the ability of communication via Modbus protocol over a variety of networks into your applications created using Borland Delphi. For the extensive list of all currently supported features please refer to that site.
• MBServer - Free ActiveX Modbus Master
  Mbserver is FREEWARE an out-process ActiveX automation server intended to communicate with PLCs or other industrial equipment that use Modbus (RTU/ASCII) protocol or Modbus TCP protocol.
• LibModbus - Linux dynamic library
  A Modbus library for Linux, Mac OS X, FreeBSD, QNX and Win32 A free software library to send/receive data according to the Modbus protocol. This library is written in C and supports RTU (serial) and TCP (Ethernet) communications. The license of libmodbus is LGPL v3 and the licence of programs in the tests directory is GPL v3.
• Jamod - Java Modbus implementation
  Java Modbus Library. This library was implemented by Dieter Wimberger.
• Paul McCrae - code examples
  Example C, VB and Visual C++ code for Linux Modbus RTU communication.
• MODBUS Serial RTU Simulator
  Modbus serial RTU simulator. Compiles with Visual C++ 6.0, and runs on Windows 2000 and probably 95/98.
• Modpoll Modbus Polling Tool
  The FieldTalk(tm) utility modpoll is a command line based Modbus master simulator and test utility. modpoll runs on Linux kernel 2.2.0 or later, QNX RTOS 6.0.0 or later, QNX 4.23A and QNX TCP/IP 4.22 or later and Win32. Other platforms on request.
• Modbus RTU and TCP ActiveX controls
  ActiveX control that provides a way to communicate with Modbus/RTU server devices connected to the PC's serial port.
• Triangle MicroWorks' Communication Protocol Test Harness
  Triangle MicroWorks' Communication Protocol Test Harness is a Windows application that acts like a typical Client or Server Device. It can be configured through a graphical user interface (GUI) and Tcl/Tk scripts to provide automated testing or simulation of your device. Tcl/Tk scripts are available to perform the conformance test procedures published by the technical committees of each protocol. The company also provides communication protocol software libraries, protocol gateways, and OPC drivers for industry-standard communication protocols such as Modbus, DNP3 and IEC 60870-5.
• Modicon SA85 Linux kernel driver
  This is a Linux kernel (2.2.19+, 2.4.7+) driver for both the Modicon ISA SA85 and PCI-85 cards. It is licensed under the BSD license. It includes source for the driver and an example client.
• "Modbus Poll" for Windows 95/98/ME/2000/XP
  A shareware program, "Modbus Poll" for Windows 95/98/ME/2000/XP, is designed primarily to help developers of Modbus server devices or others that want to test an instrumentation device. With the multiple document interface you can monitor several Modbus servers and/or data areas at the same time.
• Modbus Client and Server ActiveX Controls
  ActiveX Controls for Modbus Client and Server communications via Modbus/TCP, RTU, ASCII, and Plus. Powerful, fully-functioning HMI example application and source code are included with free trial version. No nag screens, hourly runtime limits, etc. You can completely develop and test your application(s) using the trial version, then switch to purchased verion without requiring a code modification. After 30 days, the ActiveX Controls stop communicating and return a result indicating that trial has expired. Trial period can be extended by calling Automated Solutions (+1 707-575-9631).
• Modbus Client OPC Server
  The MatrikonOPC Modbus Interface provides connectivity to Modbus compliant devices such as any PLC, RTU, DCS, etc. This server connects to multiple devices using one or more protocols at the same time. Each read/write with the devices is optimized to maximize throughput. It is a fully functioning application that can be used for 30 days after which time it must be licensed.
• uModbus 0.5.0
  uModbus or (μModbus) is a pure Python implementation of the Modbus protocol as described in the MODBUS Application Protocol Specification V1.1b3. uModbus implements both a Modbus client and a Modbus server.
• FreeModbus
  Portable Modbus ASCII/RTU implementation for microcontrollers. Ports exist for AVR, ARM7 and Coldfire processors. The license is LGPL (permits commercial usage) for the stack and GPL for the demo applications.
• NModbus
  NModbus is a C# 2.0 implementation of the Modbus protocol. It provides connectivity to Modbus server compatible devices and applications. Supports serial ASCII, serial RTU, and TCP/IP protocols. Bugs can be submitted through the project's Issue tracker.
• Modbus Constructor
  Modbus Constructor is a solution for testing and setting up the Modbus devices. Evaluation copies are available for free download. Modbus Constructor comes with a special utility, Modbus Reader, which operates using the model created with Modbus Constructor to interact with your device. Modbus Reader is a freeware program.
• MODBUS applications for the Mac OS X operating system
  ModBusProbe has been developed by Matthew Butch of Volitans Software and Rudy Boonstra of R Engineering Inc. to provide one of the necessary tools to use the Apple Mac OS X platform for industrial control. Additionally, the framework ModBusKit was released to encourage further software development.
• MBServer
  MBServer is a collection of programs and libraries offering both client and server Modbus TCP functionality. This includes both stand-alone servers and clients, as well as command line utilities and libraries which may be incorporated in your own application. The software is compatible with both Linux and MS-Windows and is licensed under the GPL as Free Software.
• Free Modbus Simulator
  Modbus RTU and TCP/IP simulator intended as a client-tester and for users commissioning HMI/SCADA applications. Well featured, emulates multiple servers at once; C++ sources available.
• PHP library for Modbus UDP Master
  This is an implementation of the basic functionality of the Modbus UDP based protocol using PHP. Implemented features include UDP Modbus master, FC3, FC16, FC23.
• ModbusPal
  ModbusPal is an on-going Java project to create a realistic Modbus server simulator. Register values are generated dynamically thanks to predefined math functions and/or Python scripts. In the future releases, ModbusPal will improve its support of Modbus standards and offer more automation mechanisms. ModbusPal relies on RxTx for Serial communication, and Jython for script support.
• Modbus Test Kit
  Modbus Tesk Kit is an implementation of the modbus protocol in Python and supports Modbus RTU and TCP for writing clients and servers. It makes the development of Modbus-capable applications as easy as possible thanks to Python. (The Python language is very flexible and easy to learn and to use.)
• Modbus4J
  A high-performance and easy-to-use implementation of the Modbus protocol written in Java by Serotonin Software. Supports ASCII, RTU, TCP, and UDP transports as server or client, automatic request partitioning, response data type parsing, and node scanning.
• Mango M2M
  Mango is browser-based, Ajax-enabled M2M software that enables users to access and control electronic sensors, devices, and machines over multiple protocols (including Modbus) simultaneously. Easy to download and install on many platforms, Mango provides an interface with which diverse data sources can be created and configured while providing downstream management of user access, alerts, data logging, and automation.
• Wireshark
  Wireshark® is a popular network protocol analyzer. It has a powerful feature set and runs on most computing platforms including Windows, OS X, Linux, and UNIX. It is freely available as open source, and is released under the GNU General Public License version 2.
• simple-modbus
  SimpleModbus is a collection of Arduino libraries that enables you to communicate serially using the Modicon Modbus RTU protocol. Both SimpleModbusMaster & SimpleModbusSlave implements function 3 and 16 in addition SimpleModbusMaster implements function 1, 2, 4 and 15.
• Open-source Modbus Library in C#
  Open-source Modbus library (client/server) for Modbus ASCII, Modbus RTU, Modbus TCP, and Modbus UDP. Written in C#, the code library is designed for implementation in .NET projects.
• Open Source ModbusTCP Library for Delphi
  A set of Delphi components to communicate with a Modbus PLC over TCP/IP. The library provides components to implement both a Modbus client and a Modbus server, and is based on the Indy component set (both Indy 9 and 10 are supported).
• RModBus
  RModbus is a free Ruby implementation of the Modbus protocol. It supports Modbus RTU and Modbus TCP as client or server. For the extensive list of all currently supported features please refer to the web site.
• Modbus TCP, RTU, and ASCII Master Drivers for .NET
  Automated Solutions ASComm.NET is a fully-managed .NET component that delivers communications connectivity between .NET applications and a broad range of industrial devices/protocols including Modbus TCP, RTU, ASCII. ASComm.NET also supports Ethernet communications with A-B Logix Family, PLC5, SLC500, MicroLogix, and GE SRTP compatible controllers. ASComm.NET supports advanced features such as visual design (can be configured programmatically or visually), background scanning of data items at specified rates, data change and error events, and serialization. Free 30-day, fully-functioning trial available for download.
• CAS Modbus RTU Parser
  Analyze Modbus Messages. Type in a string of hex bytes and the parser will break the message out for you showing you destination, function, data.
• CAS Modbus Explorer
  Attempts to connect to RTU devices using various permutations of Baud, Data and Stop and data point until it makes a connection for you.
• CAS Modbus TCP Parser
  A Utility to retrieve coils, inputs, holding registers, and input registers from a Modbus-TCP-enabled device.
• Open-source multi-platform Modbus libraries for .Net
  Cet Electronics offers a series of open-source Modbus libraries written in C#. They support RTU (binary only), TCP and UDP, both client and server. The libraries target .Net Micro Framework, Windows Phone, and standard .Net (incoming). High abstraction for easy pluggability, and extensibility. Multi-threading and C# 5 are supported. Very easy to use.
• Go Modbus
  Fault-tolerant, fail-fast implementation of Modbus protocol in Go language. Incubating - do not use in production yet (more testing needed).
• Updated Free Modbus Simulator
  Free Windows Modbus RTU and TCP/IP server simulator that supports the full range of Modbus addresses for all four Modbus types (0xxxxx, 1xxxx, 3xxxx, & 4xxxx addresses). Diagnostics include complete traffic byte capture and logging capability with human readable decode descriptions. Multiple Device IDs can be simulated at one time. Supports CSV loading and a scripting environment for testing purposes as well as HTML custom displays. Written in Visual Studio C++ 2010 with full source code available. Extensive help is available by using the built-in key. This is a fork/extension of the "Free Modbus Simulator" also listed here.
• JLibModbus
  JLibModbus is an implementation of the Modbus protocol in java language. jSSC and RXTX are used to communicate via serial port. This library is an actively tested and improved project.
• Unserver CE
  Unserver is a new way to communicate to Modbus devices. It allows developers to organize Modbus addresses into logical groups (tags) and get/update values via HTTP RESTful API with support for caching, polling, data type conversion and logging. It can run as a console application or as a background service. The free version is fully featured, but the duration of one working session is limited.
• MSS Modbus TCP Server Simulator
  MSS is free Modbus Server Simulation software. It enables users to prepare any scale of simulations from scratch. It supports Class-1 Functions, 64K addressing and Bit, Int/UInt8, Int/UInt16, Int/UInt32, Int64, Single and Double Data-Types in all four data-endianess. With MSS, user can map registers and assign data to them without struggling with hex values, data-lengths or endianess. Users can also connect other TCP Servers to copy register mapping along with register data. MSS is a small and portable application that runs on Windows version XP and above.
• CAS Modbus Scanner
  A Utility to retrieve coils, inputs, holding registers, and input registers from a Modbus-enabled device.