LabVIEW 7.1 & Windows Server 2003 strange network behaviour

[_EMG_]

Hello,

I know that Windows Server OS is not directly supported by LabVIEW, but we have an application with this constellation:

The system was working now for about 2 years without problems. The App is for a measurement system and has three separate network connections:

- The first connections is a client wich connects to a PLC (wich is server) using Modbus TCP (NI library)

- The other two connections are implementet as TCP Server and the line PLC connects as client using TCP/IP protocol

Now the probem, when one of the line PLC clients connects the Modbus connection hangs up for about 15..20 seconds. The connections is not interrupted, just no more telegrams

are send or recieved. After this time everything is normal again.

I've seen that in the moment the line PLC connects to the Listener the other connection "takes a break", when the listener loop is left everything is normal.

This behavior happend after an update of the LabVIEW application (well, my first thougth was the update was problem, too!), but when I start the previous version wich didn't had that behavior, it now have the same problems.

What might be this ?!?! Any help?!

[DianaS]

Hi,

what did change on your system? Which Labview version did you have before?

Are there any windows updates?

How do you know your problem did not occur in the version before?

Did you change any firewall or network settings?

[_EMG_]

Hello Diana,

thanks for your answer.

The LabVIEW version is still 7.1, it hasn't changed. The only change was the EXE file of the application.

The "automatic windows update" is turned off, also the Windows firewall.

I can see in historical data that the charts don't have unvalid data in the time when line PLC connects to

the server.

The only change is that the customer had installed a firewall, but the PC and line PLCs are installed behind the firewall.....

[DianaS]

Hi,

is the example from the modbus-library working there?

Can you try this?

You find the master and slave TCP example like in the attached screenshot.