The OMRON TCP/IP device communication enabler communicates using FINS commands over Ethernet. The FINS commands are exchanged between the computer running a Proficy CIMPLICITY project and the controllers in UDP packets. UDP packets are called datagrams. Datagram communication is termed connectionless communications in contrast to TCP, which is connection oriented communications. With datagram communications, the controllers can communicate with more devices since they do not need to maintain a separate and distinct connection for each device.
UDP datagram service does not guarantee packet delivery, as does TCP. The communication enabler always expects a response for each issued read or write command. If a response is not received within a time-out period you configure, it will retry the command for the number of retries you configure before concluding that the device is "down" or unreachable at the designated address.
UDP datagrams are sent and received over abstractions called sockets, which can be likened to serial communication ports. Multiple sockets can be opened for a given Ethernet interface; hence, the OMRON TCP/IP communication enabler can "share" the Ethernet port with other applications running on the same computer.
OMRON TCP/IP application notes.