Jump to content

OPC UA will not reconnect


Recommended Posts


my system : USP-104-X10 with B10

I have 3 PLC's (all same model and firmware (1.33.161)) communicating via OPC UA server with Kepware

Everything is working perfectly.....until I stop my Kepware (to do some upgrading or other stuff)

When I shutdown my Kepware I see following OPC-AU diagnostics differences :






You see the difference in the current session of current subscription count -> PLC A is 0 and on PLC B it stays on 1....

When I restart my Kepware, I'm able to reconnect on PLC A, but not on B !

My Kepware gives me following error



The PLC B is actually refusing the communication

The only thing is to give a cold boot on the PLC B to restart my communication...

I checked (several times already 😒😒😒) all parameters (on PLC side and on KEPWARE) but all are the same...

any suggestions ?


Link to comment
Share on other sites

Hi @pascal,
I can see when you shutdown
Kepware PLC B "Current Session Count" stays on 1. 
If i understand you, no other clients are connected to the PLC, and it should be 0 when Kepware is down. (Like PLC A)
It means the PLC server doesn't recognize the client is down, and when you try to connect again you get refused because of unclean exit.
I tried to simulate with UaExpert client and two OPC-UA server PLC's,  but in my set-up everything works.

To be able to help you more please open a ticket on Unitronics "Help center" at https://support.unitronics.com/index.php the Support team will assist.

Link to comment
Share on other sites


with UaExpert, when disconnecting the server, my counters goes from 2 to 1 (because kepware is also connected)...

But ....

today I was trying some more things on my kepware and everything is working fine now.

The thing is, I didn't changed anything. Not on my PLC and not on my Kepware...

(altough I deleted on PLC side some  not used communication protocols ( on CPU, deleted 1 UDP port I didn't used anymore and 1 TCP server with 16 number of connections, also didn't used))

Last friday this hadn't brought me a solution.

When I started checking on monday again, suddenly it worked ???????


I still have to check some things with our IT department to know why it works (now).....

I'm not accusing somebody, but most of my communication problems are IT related 😁😁😁(and they never never did something) 


When I had al the trouble (last week) and I disconnected Kepware and my UaExpert, the number of connected clients went from 2 to 1(unclean exit Kepware and clean exit of UAexpert), but after the not clean disconnection of Kepware I couldn't even connect again with UaExpert....

I'll keep you all informed of my situation.....



Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...