Hi,
This behavior does not surprise me. I used to have many serial modbus devices via Ethernet-to-serial device servers. Whenever one of the units of a particular serial port went down, Lookout would cripple itself trying to get data on that dead or non-responsive device, messsing up all the other devices, especially ones on the same port. A long time ago, there was a request (mine included) to add functionality to all serial devices in lookout, but especially Modbus and Ascii devices, to allow switching each Lookout device/port on and off (add enable/disable data member) to mitigate this problem.
The way I was able to circumvent this issue was with an Ethernet Modbus Gateway from Moxa (MB3480 in my case). With this device, Lookout does not see loss of a serial device or even an entire port on the Modbus Gateway as a loss of port communications (it is the port comms that messes up Lookout as far as I can tell, not the device comms exactly). Instead, the Gateway handles all the "port" comms for Lookout and an offline device's or port's "no response" is handled just as it should be. Of course the other advantage of using TCP-to-serial gateway is that more than one Lookout server can access the serial devices at the same time. This makes for better redundancy and failover.
Unfortunately, it seems each TCP Modbus device is handled as it's own "port" in Lookout, so unless Lookout fundamentally changes how bad ports are handled, you are going to be out of luck I would guess. Hopefully Ryan can come up with a workaround for you.
This is an area that Lookout has needed improvement in for a very long time, and the lack of improvements has kept me away from TCP-modbus device comms. Instead, I've stuck with RS-485 device comms and coupled them with TCP/Serial gateways.
Cheers,
Ed
Message Edited by erblock on 01-14-2009 04:47 PM
