ModbusMaster

Standalone Windows app supporting Modbus RTU , TCP , UDP , RTUoverTCP , RTUoverUDP , ASCIIoverRTU , ASCIIoverTCP and ASCIIoverUDP protocols.

Also included are its Mono versions for Linux and Mac OS X, these are VB Net versions so:

• For Linux you will have to install mono-complete and mono-vbnc packages
• Mac might be different depending on the OS X version, maybe install mono and mono-basic packages

If a firewall is enabled then it might prompt you to allow this app to communicate on the network:

• Normally it should be allowed to communicate on the private network otherwise it might not work properly
  • Do not allow public access unless you know what you are doing
• Once the testing is done then remember to remove this app from the firewall's list of allowed apps

The app is designed to allow running multiple instances of the app at the same time, for example:

• Use the same protocol for each instance but with different port numbers, similar to:
  • IP 127.0.0.1 TCP Port 501 and IP 127.0.0.1 TCP Port 502
• Use a mix of different protocols with help of other tools (like com0com for RTU protocol on Windows)

This is all based on modified nModbus .NET 3.5 libraries, Copyright (c) 2006 Scott Alexander:

• These are included as a resource for Windows version but are separate for Mono version

Intended to be used as a quick testing tool:

• Can be tested with its counterpart ModbusSlaveSimulation (check the video further below)

An easy alternative to use instead would be the AdvancedHMI software since it is highly functional and free.

Screenshot

Functionality

• Read the comments inside the form and also hover the mouse over the labels for hints.
• No Offset Addressing (where xxxxx goes from 00000 up to 65534):
  • Coils = 0xxxxx
  • Discrete Inputs = 1xxxxx
  • Input Registers = 3xxxxx
  • Holding Registers = 4xxxxx
• Apart from Int16, which is register adress only without modifier, this app also supports:
  • U, F, L, UL and S modifiers ( which are used for UInt16, Float32, Int32, UInt32, String )
• A support for 64-bit values was added - Float64, signed and unsigned Integer64:
  • Use FQ, LQ and UQ modifiers ( where Q stands for Quad Word )
• An experimental support for 128-bit values was added - signed and unsigned Integer128:
  • Use LO and UO modifiers ( where O stands for Octa Word )
• It also supports bit/character Reading/Writing:
  • select either consecutive bits/characters within a single element or the exact individual bit/character from each of the multiple elements
  • either a single value or the exact number of comma separated values will be required for writing if Points number > 1
• For RTU based protocols, on a single PC, this app can use the help of:
  • The com0com Windows program to provide virtual serial port pairs
  • Additional TextBox allows manual input of the serial port, intended for Linux so tty0tty virtual port pairs, like /dev/tnt0 <=> /dev/tnt1, could be accessed
    • This box was removed in the Mac Mono version
• The library supports Masked Bit Write, function code 22 (0x16H or FC22)
• The app also includes the built-in code for slave devices that don't support FC22:
  • This entails read-modify-write process which can take a little time and could overwrite values that changed during its running

IMPORTANT: Exercise caution when attempting to write any value to the PLC.

Usage

-> For Windows

• Either use the Windows executable files from the exe folder or follow the instructions below to build it yourself:
  • Download and install Visual Studio community edition (ideally 2019)
  • Download and extract the zip file of this project
  • Open this as an existing project in Visual Studio and, on the menu, do:
    • Build/Build Solution (or press Ctrl-Shift-B)
    • Debug/Start Debugging (or press F5) to run the app
  • Locate created EXE file in the /bin/Debug folder and copy it over to your preferred folder or the Desktop

-> For Mono

• Make sure that Mono is installed on your computer:
  • Both mono-complete and mono-vbnc packages for Linux
  • For Mac you might need to experiment, maybe install mono and mono-basic packages
• Download and extract the zip file of this project and locate the Mono zip archive in the Mono folder
• Extract 4 files and potentially rename the newly created folder and/or exe file to something shorter if you wish, just to make the terminal navigation quicker
• Open the terminal, navigate to the folder and type: sudo mono ModbusMaster.exe:
  • On Mac you might need to switch to the superuser su account
• For testing RTU protocols, on Linux you can possibly install and use tty0tty virtual port pairs while on Mac the later OS X versions seem to have pseudo terminals - pairs of devices such as /dev/ptyp3 <=> /dev/ttyp3

Note for Mac users: this was tested on an old iMac G5 PowerPC computer with Mono v2.10.2. Some odd behaviour was present in a sense that the app was loosing focus thus disrupting TCP communication in Auto Read mode. There is a text box with red X that you can click to try to maintain focus (if you do something else afterwards then click it again). Since I cannot test it in any other way then it is left for you to experiment.

Video

Modbus.TCP.Communication.mp4

License

Licensed under MIT license - see the README.txt file inside the Resources folder.

Trademarks

Any and all trademarks, either directly or indirectly mentioned in this project, belong to their respective owners.

Useful Resources

The AdvancedHMI website forum, which is another open source project.