Modsak - Modbus diagnostic program

Modsak is a versatile Modbus diagnostic program. It will be of interest to device manufacturers, software developers, system integrators and field service engineers. Modsak can be used to test or simulate almost any device or system that uses the Modbus protocol: slave devices, PLC's, HMI's, MMI's, DCS's, RTU's, SCADA systems, bridges, gateways, device servers, etc.

If you are a device manufacturer, you can connect Modsak to the device you are developing to test its handling of the Modbus protocol and also its general operation. Software developers can use Modsak to simulate the environment (Modbus masters, slaves and bridges) in which their software has to operate. System integrators can plug Modsak into a system to temporarily replace Modbus components they don't yet have; or when components refuse to talk to each other Modsak can be used to try out different configuration settings. Modsak running on a portable computer will be a valuable tool for field service engineers, enabling them to monitor the communications between system components, or to send their own requests to the Modbus slaves in the system.

Modsak's main features are:

  • Can be configured to run in one of four modes:
    • Manual master mode, where the user can send individual requests to a Modbus slave.
    • Automatic master mode, where it continually polls (sends read and write requests to) a Modbus slave.
    • Slave mode, where it simulates a Modbus device.
    • Monitor mode, where it relays messages between a Modbus master and a Modbus slave. In monitor mode, Modsak may be used like a breakout box or protocol analyzer to observe the messages being exchanged between a master and a slave. Monitor mode also allows Modsak to be used as a gateway or bridge.
  • Full support for coils, discrete inputs, input registers and holding registers, using commands 1, 2, 3, 4, 5, 6, 7, 8, 11, 15, 16, 17, 22 and 23.
  • Supports network and serial (RS232/RS422/RS485) interfaces using the Modbus/TCP, RTU and ASCII protocol variants.
  • Cross-platform: runs on any system that supports Java 1.4 or later - including Windows, Linux, Solaris and AIX.
  • All known extensions of the Modbus protocol for handling 32-bit and 64-bit integers and floating-point numbers are supported (including Enron/Daniels Modbus).
  • Can transfer a mixture of integers and floats, of different sizes, in a single message.
  • Flexible address mapping allows separate or overlaid address spaces (for coils, discrete inputs, input registers, and holding registers) with arbitrary bases.
  • Registers are individually configurable for type (integer or float), size (8/16/32/64-bit), and radix (binary, octal, decimal, or hex).
  • Supports broadcast requests (slave ID 0) in both master and slave modes.
  • Full support for 0x0A ("Gateway Path Unavailable") and 0x0B ("Target Device Failed To Respond") exception responses.
  • Informative interpreted trace of all Modbus messages sent and received.
  • All configuration settings may be saved to and restored from a file, in XML format.
  • Online manual/troubleshooting/HOWTO facility.

Modsak main window

The Modsak demonstration lets you try out Modsak's user interface using your browser.

Better still, you can download the complete version of Modsak for a FREE 3-DAY EVALUATION PERIOD - read on for details.

Downloading and installing Modsak

Since Modsak is written in Java, you will need a copy of the Java JRE (version 1.4 or later) in order to run it.

To install Modsak simply download the file modsak1.36.jar from the products page, and put it in any convenient directory/folder.

To run Modsak, use the command:

java -jar modsak1.36.jar

You will, of course, need to use the full pathname for modsak1.36.jar if it's not in your current directory/folder. You will probably want to create a shortcut, launcher, shell script, or whatever to save you having to keep typing the above command.

If you get an error from the "java -jar modsak1.36.jar" command, try the command:

java -version

If you get an error from this command, then you do not have the JRE installed, and you will have to download it (see Getting Java).

Before you can use Modsak you will need to get a registration key.

Problems?

If you have any problems setting up the Java environment, installing Modsak, getting a registration key, or using Modsak, please email us at support@wingpath.co.uk and we will do our best to help.

If you are reporting a bug, please give a full description of what you were doing and what went wrong. Include all the information displayed in the Help->About dialog, and also any output that was sent to the command window.