Modbus connection error

Hi, I have a PLC connected through Modbus ethernet and all is working fine but sometimes I was disconnected and get errors in the console, this happen mostly when I continued my work the next day. The solution for now is reset the gateway and works again.

Here is some screenshot:




The first error is the Modbus device closing the connection. This typically happens after 10-15 seconds of inactivity. If you haven’t setup and subscribed to any tags yet then this isn’t surprising.

I have setup some tags and all works perfectly, I had that error when I turn on my computer after has been shut down all night.

My question is: Ignition is closing the port? or is my plc?

The way I solve this is resetting the gateway, but I can’t tell that to my client every time it happen.


It’s always the PLC that closes the port.

You have to be subscribed to tags - not just have them mapped in the gateway. If you haven’t created any tags in Ignition yet after creating that mapping you’ll still see the periodic disconnects.

I have the tags in Ignition working, displayed en diferent windows, in transaction groups writing to database etc. and still get that error.


What rate are you subscribed to the tags at? These tags are from the 192.168.2.5 device, right?

The tags are in default rate, 1000ms, the tags are from the 192.168.2.5 device.

Hmm. Not really sure what the cause is then. The only thing I can tell you is that message means the device closed the connection.

When you said that the plc close the connection because inactivity, What happen if I shut down my PC, the plc close the connection as well?

When I get this errors in the console, if I reboot my PLC it doesn’t work either, That is why I think Ignition has the problem because if I reset the gateway all works fine again.