Issue
Many Modbus Tester software packages do not support testing a Modbus RTU connection over Ethernet, where the packet passes directly through a hardware Ethernet connection to an RS-485 level converter (not a protocol translator).
Product Line
Devices with EtherGate functionality
Environment
Windows
Cause
The Modbus tester tool is coded to use TCP port 502. When testing a TCP connection, the port settings cannot be modified such that other protocols could be tested. The EtherGate protocol uses different TCP ports and therefore Tester would not be able to establish communication with the downstream Modbus RTU device.
Resolution
This article describes how to test an EtherGate connection using the MBMaster program:
A command line program developed by Schneider Electric to help troubleshoot Modbus TCP, Modbus RTU (serial) and Modbus RTU over TCP connections.

Attached is a customizable batch file used to run and configure the MBMaster program. The installation steps are shown below:

• Unzip and copy the MBMaster folder to your C:\   (root directory)
• Right click on the MBMasterConfig.bat file and select edit¹.
• Follow the editing instructions that are contained in the file.
• Save & close the file (replace the old one if needed).
• Double click on the MBMasterConfig to execute the program.
• The program will run for about 10-30 seconds and display the requested data registers if successful.
• A .txt file will be saved in the MBMaster folder containing the results of the executed operation².

Example of a successful response



Example of a bad response

​

Notes,
1 - MBMasterConfig.bat file can be copied & pasted to the desktop if you find it easier to execute from there instead of in the MBMaster folder. However, the folder needs to be located in the C:/ directory.
2 - The .txt file is named Modbus by default, but it can be renamed using MBMasterConfig batch file.