I have already written two blogs about Ethernet/IP. The first one described the features of the protocol as well as the proprietary services that Rockwell uses to communicate with its devices (Micro, CompactLogix, and ControlLogix class PLCs). The second one dealt with the practical configuration of communication with PLCs of the CompactLogix and ControlLogix classes.
This is a companion discussion topic for the original entry at https://d2000.ipesoft.com/blog/communication-ethernetip-and-encapsulated-pccc/