TCP Write Error

[Hemagopal]

Hello

I use LabVIEW 2009 SP1. I use TCP VI s to do Modbus TCP communication. I get Error 61 which says Serial Port Parity Error, The System could not allocate the necessary memory. Is it because of the TCP stack overflow. Or should there be some amount of time delay between TCP Write and TCP Read. Please let me know. Thank you.

- Hema

[mikeporter]

What were the circumstances surrounding the error? Does it happen all the time? What does you code look like? Can the two computers ping each other?

Mike...

[Hemagopal]

Hello Mike, The error 61 occurs randomly. We ping the device with its IP address every second and also read the registers thru TCP. For an hour everything runs OK. But then the error occurs sometimes after an hour, sometimes after two hours, randomly. About the code, I will be sending what exactly is done in TCP. We read the registers in LabVIEW similiar to Modbus poll. 

Thank you.

[JÞB]

although I'm not finding the right link today, I seam to recall that this bug has been reported before.  (random inability to establish a TCP connection if planets allign just right)

Supposedly this is fixed in some version of LabVIEW later than 2009 (was it 2011 or 2012? I'm not finding it in the release notes)

The network itself is sometimes a problem.  Noise and such those eye diagrams only really tell you how uncommon a bad transmission is not how often they occur- the eye will close sometimes.

In the past of had to code in retries to aliviate problematic TCP connections.

[mikeporter]

Yes, Jeff has a good suggestion. For intermittent problems like this, after each try, check for this specific error and is if occurs, reconnect and try again. If the error is still there after a couple tries or so, then report it.

Obviously, if you get any other error stop immediately.

Also, how far apart are these computers? Is there anything between them other than wire (routers, switches, etc...)?

Mike...