Never had problems with plc simulator. Probably you need to check the plc simulator configuration, or to check with a sniffer what packets you are sending and receiving.There are some videos on youtube on how to use wireshark, if you are using modbus tcp.
I ve been trying to get data from an SMA sunnyboy solar inverter with the Modbus TCP protocol for some time now.Theare are lots of libraries for modbus serial both master and slave as well as modbus tcp server/slave. However I was unable to locate a library for modbus tcp working as a client/master. 2b1af7f3a8