Does your PLC work via Ethernet or com port ? Can you make a log of Wireshark or monitoring program for COM port and put on the file exchanger ?
With the exact model of PLC ? and the type of exchange Protocol ?
Sure, it is an Allen Bradley Compactlogix L33ER EtherNet/IP. The used protocol is OPC. Here is the Wireshark Log, of course some of the parcels shown here were inexistent before installing the OPC server.