Oh good. I was just about to ask about an issue involving VFDs that don't see a missing master (client) as a problem when using explicit messaging. ABB mentions something about that not being a part of the EtherNet/IP spec and has a parameter to force the drive to fault if no messages come in after it was told to run. But I am not playing with an ABB drive.
The Yaskawa will fault if it loses the connection from an implicit controller, but not from Do-more/BRX explicit messages loss (unless the patch cable from the Ethernet switch to the VFD is unplugged, which is a very limited cause.) Modbus/TCP master loss WOULD fault it, but that's a different card.
So, in the meantime, is there any way to make a server(slave) device know it lost a connection and not that it was closed? The browser web page for the Yaskawa SI-EN3 doesn't even show a connection in the network status even though the BRX is sending it read/writes 135 times per second. A connection from a CompactLogix shows up just fine.