Hi mischaivchenko,

Three things I would consider trying are,

What happens if you use Mango's tools on the Modbus Data Source page to read these registers? Do you get better feedback, or output to the log file? The point locator test tool uses the same method you are using. Can you attach a debugger? Modbus4J is open source and as far as gaining knowledge in Java goes, you should be able to attach a debugger in your IDE and step into the code. Get a log4j configuration that will output the various log statements from TcpMaster and pass that into your program as a command line argument.