Mitsubishi Q Series Connection issues

Hello everyone,

I am setting up a new Cell Assembly line and everything on the line is currently using Q-Series PLCs (I am not a fan of these based off past experiences in other MES systems).

I am using Ignitions native OPC server since it would be great to not need Kepware/MX OPC. I have the latest ignition 8.1.33 installed and the latest Mitsubishi module. I am having an issue where we get connected successfully to all of the devices, but anytime I restart Ignition, the OPC module, or lose a connection, the PLCs (most of the time) don't come back online in the gateway and sit at reconnect/Wait. I can ping the PLC without issue, but no connection to Ignition. Doing a reset on the PLC itself will resolve the issue temporarily.

Working on this with IA support, they believe the PLC network card is not freeing the port up (port 1025) after a disconnect and then closing ignition out of the next TCP request. I reached out to controls, and they state that the PLC is online and the settings in GXworks is all correct according to the ignition documents.

I ran Wireshark capture from the firewall and the switch port connecting to one of the PLCs (.30) while I had it disconnected from the ignition.

Looking at the captures for some other PLCs (.33 for example) I can see TCP connection requests from the ignition server being constantly rejected by the PLC on port 1025.

I am not sure what to do from here. I am tempted to just set up Kepware and see if the issue occurs there as well since I don't fully trust the new Mitsubishi drivers. I have no window into the PLC world here so I can only take their word for it before trying to get Mitsubishi themselves involved for support. Any other thoughts?

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Only tangentially related, but...

restarting the OPC module shouldn't be a regular occurrence. There is no reason to be doing this.

The Mitsubishi PLCs are finicky about TCP connections. They allow one per configuration entry. If the connection isn't closed properly, or something prevents the PLC from thinking it's closed properly, then it's going to behave exactly like you're seeing until the socket/connection times out in the PLC software stack.

edit: also make sure you don't have some other Ignition gateway connected to the same PLCs, like e.g. a development gateway, or a Kepware instance, or literally anything else that might use that one configuration entry.

Thanks for that information. The behavior comes from more than just restarting the gateway or the OPC module. We have had the issue occur when adding devices, adding or updating tags, etc.

Can I assume that the controls engineers can ensure the connection is closed or reset properly? Maybe they adjust the connection timeout?

I'm not sure what configuration options are available on the PLC side.

Ignition will only give up a connection to the PLC when you edit/save that device entry, when you restart the OPC UA module, or when you restart the Ignition Gateway. You can look at Wireshark when this happens and verify that Ignition is sending a TCP FIN to close the connection.

In any other case you lost the connection due to something on your network or PLC side and it's external to Ignition.

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