ModbusSlaveSimulation

Standalone Windows app supporting Modbus RTU, TCP, UDP and ASCIIoverRTU protocols for simulation.

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)

The app should service requests for any valid Modbus slave ID.

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 ModbusMaster (check the video further below)
• Or maybe use the AdvancedHMI software instead since it is highly functional and free.

Screenshot

Functionality

• All values can be set before the connection is established - Coils, Discrete Inputs, Input Registers, Holding Registers.
• The Data Grid View is set to initially show 20 rows of addresses but can be changed within the Row Count dropdown to show more or all rows if necessary.
• In the Data Grid View, selected with the I/O Address Range dropdown, double-click the value to change it:
  • Boolean values will flip between 0 and 1
  • Uint16 values require unsigned integer value between 0 and 65535
• Discrete Inputs and Input Registers provide read-only access to the Master application:
  • MODBUS device designated as Master can ONLY send requests to read these values
  • These values should be manipulated by the user directly in the simulator otherwise they will not be changing
• Coils and Holding Registers provide read/write access to the Master application:
  • MODBUS device designated as Master can send requests to read these values as well as send requests to have these values be modified
  • These values can also be manipulated by the user directly in the simulator if necessary
• For RTU and ASCIIoverRTU protocols, on a single PC, this simulator can use the help of:
  • com0com program for Windows to provide virtual serial port pairs
  • tty0tty program for Linux to provide virtual serial port pairs
• Additional TextBox allows manual input of the serial port:
  • Mainly intended for Linux so those tty0tty virtual port pairs, like /dev/tnt0 <=> /dev/tnt1, could be accessed
  • This box was removed in the Mac Mono version
• The library also supports Masked Bit Write, function code 22 (0x16H or FC22).

Usage

-> For Windows

• Either use 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 Desktop
• For testing RTU protocols use com0com to create virtual serial ports

-> 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 mono and mono-basic packages
• Download and extract the zip file of this project and locate Mono 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 ModbusSlaveSimulation.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 ports while on Mac the later OS X versions seem to have pseudo terminals - pairs of devices such as /dev/ptyp3 and /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 continuous TCP communication. 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 also 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.