Why does UDP Read only work sometimes?

[psu256]

I am having a heck of a time getting UDP read to work on my PXI system. The system has two PXI-8231s installed, and I have two VI's running, each of them sitting in a while loop calling UDP read for each of the cards. I'm not simply missing a packet or two, it is a wholesale yes or no whether or not any data gets to me. I can see the packets come in on ethereal... seemingly random acts such as minimizing the vi's front panel will make a vi that didn't see any traffic suddenly spring to life! I am totally baffled... and I really need to get these vi's to receive data.

Any suggestions on how to troubleshoot this??

Angela

[SimonH]

Angela,

Have you tried just running one loop and one card to see if the problem is related to the parallel loops/multiple cards?

What do you have set for the timeouts of the UDP read VIs?  Also does every parallel loop in your application have a wait statement or some other way to ensure that one loop doesn't starve the others of processor time?  Another thing you could check is your processor usage while the VIs are running -- this would give you some indication of whether or not your application has any loops that aren't playing nicely with the others.

Regards,

Simon H
Applications Engineer
National Instruments

[psu256]

Well, I think I may or may not have found a clue... we have two devices, the PXI rack being one of them, that we configured to use the same IP address, since only one of them will ever be on the network at the same time. So in theory we could swap between them with minimal effort. I noticed that even though the switch we were plugged into had been powered off and reset, still has a destination that has the other device's MAC address. I don't know if this is the issue or not, but it has me highly suspicious.