Download of ModbusServer 4.03 for Mac was on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The software lies within Design & Photo Tools, more precisely Presentation Tools.
This free software works fine with Mac OS X 10.6 or later. The most popular versions of ModbusServer for Mac are 3.1 and 1.0.
According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software. This free software for Mac OS X was originally created by Control Technologies Pty Ltd.
From the developer:
Modbus TCP Server simulates Modbus Holding, Input and Output registers 0 to 65535 according to Modbus specification 1.1b. Simulate Modbus devices to facilitate software development and observe the raw data exchange between server and client.
You may want to check out more software for Mac, such as NeoRemote, Soundslides or Motion Backgrounds, which might be related to ModbusServer.