Modbus Simulator & Tester
Modbus Poll - Witte Software (ModbusTools)
Modbus Poll is a Modbus master simulator designed primarily to help developers of Modbus slave devices or others that want to test and simulate the Modbus protocol. With the multiple document interface you can monitor several Modbus slaves and/or data areas at the same time. For each window you simply specify the Modbus slave ID, function, address, size and poll rate.