Modbus scan software


I have a problem when using modbus scan software such as modscan32 or mdbus when connecting to PLC through serial link all is ok however through ethernet I got the error modbus/TCP connection failed!

Any idea of what could be the problem?

Thank you!

CAS Modbus Scanner is a utility to retrieve coils, inputs, holding registers, and input registers from a Modbus-enabled device. Values retrieved from the device can be viewed in many different formats, including Binary, HEX, Uint16, Int16, Uint32, Int32, and Float32.