Modsak - Modbus diagnostic program

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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 other main features are:

  • Can be configured to run in one of three modes:
    • Master mode, where requests can be sent to a Modbus slave. The user can send individual requests, and Modsak can also continually poll (send read and write requests to) the 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, or as a simple protocol converter that converts between Modbus protocol variants.
  • Cross-platform: runs on any system that supports Java 1.5 or later - including Windows, Linux, Solaris and AIX.
  • Manual and troubleshooting guide.
  • Command (and command sequence) definitions may be saved for re-use.
  • Informative interpreted trace of all Modbus messages sent and received.
  • Logging of all register reads and writes.
  • All configuration settings may be saved to and restored from files, in XML format.
  • Register definitions may be imported/exported in CSV format.
  • Full support for coils, discrete inputs, input registers and holding registers, using the following commands:
    • 1 Read Coils
    • 2 Read Discrete Inputs
    • 3 Read Holding Registers
    • 4 Read Input Registers
    • 5 Write Single Coil
    • 6 Write Single Holding Register
    • 7 Read Exception Status
    • 8 Diagnostics
    • 11 Get Comm Event Counter
    • 15 Write Multiple Coils
    • 16 Write Multiple Holding Registers
    • 17 Report Slave ID
    • 22 Mask Write Holding Register
    • 23 Read/Write Multiple Holding Registers
    • 43/14 Read Device Identification
    • Custom commands
    • Invalid commands - for testing the slave's error handling
  • Supports network and serial (RS232/RS422/RS485) interfaces using the following protocol variants:
    • Modbus TCP (also known as Modbus TCP/IP)
    • Modbus RTU
    • Modbus ASCII
    • Modbus RTU encapsulated in TCP
    • Modbus ASCII encapsulated in TCP
    • Modbus UDP (also known as Modbus TCP encapsulated in UDP)
    • Modbus RTU encapsulated in UDP
    • Modbus ASCII encapsulated in UDP
  • All known extensions of the Modbus protocol for handling 32-bit and 64-bit integers and floating-point numbers are supported (including Enron/Daniel 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 (1/8/16/32/64-bit), radix (binary, octal, signed decimal, unsigned decimal, hex, or char), and scale/offset.
  • Supports broadcast requests (slave ID 0) in both master and slave modes.
  • Full support for exception responses 10/0x0A ("Gateway Path Unavailable") and 11/0x0B ("Target Device Failed To Respond").

You can download the complete version of Modsak for a free 3-day evaluation period.

Screenshot

Modsak main window