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Wrong value of "General -> VNC Number Of Connections"


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General.VNC Number Of Connections INT32 on a Unistream 15.6" is linked to an HMI numerical display and the "connection counter" seems to be cumulative instead of real time. Right now it is showing "D#6" and there is absolutely NO WAY there are  six active sessions at this instant in time. UniL version 1.19 rev 19. Have noticed this for about a year. This in no way inhibits crucial functionality of the process control, just a nuisance to me. In short the VNC connection counter seems to get STUCK. A reboot will zero it back out. Sometimes it works as expected; ie showing zero, then 1 when I connect VNC and back to zero when I disconnect.

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5 hours ago, NoamM said:

checking the issue. Will update ASAP.

Great, not sure if it will present in a LAN environment or not. All VNC clients are on WAN side. Router is DMZ to PLC (panel) IP. My only theory is when multiple clients connect at the same time (which can happen) and then disconnect in random sequence that (perhaps) PLC not detecting disconnect. Not really sure of the mechanics of a VNC session disconnect on host side. I know at 2am that six clients are not still connected. Mobile devices are mostly iphones, if that helps. Operators spot check panel when they get a text msg alarm. Doubtful anyone is staying on 24/7 via their cell phone. Thanks for looking into it?

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  • 11 months later...

Hi hotwires,
This is just the way TCP works. A connection can remain established for days or even weeks without a single packet being exchanged. The disconnection should be detected as soon as the connected side tries to send data. A disconnected device can't send any data, so there's no way to  know that it's disconnected until it fails to respond to a query.
In general, the only way to detect a disconnected device is to try to send data to it. If you don't ever send any data, you're simply not assured of detecting it.

      When the server regains connectivity (back on the net) it will automatically update the number of connections value.

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