Modsak Manual v3.10 - 1.1. Overview
Modsak is a versatile Modbus diagnostic program that can be used to test or simulate almost any device or system that uses the Modbus protocol.
Modsak can be configured to run in one of three modes:
Master mode, where requests can be sent to a Modbus slave.
Modsak provides two ways of sending commands to a Modbus slave:
Slave mode, where it simulates a Modbus device, receiving requests from a Modbus master (or masters) and responding to those requests. In this role Modsak provides storage and retrieval of values in registers, but does not provide any logic to operate on those values.
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.