Lost connections

I am still evaluating this SCADA system. The connections was working fine 2 weeks ago. But since last week, I could not see live tags from RSOPC server though I could still see the PLC. While trying to solve that problem yesterday, something happened, I lost all connections. Please see the screen copy for the alarm I got from connection test. In fact, this happened many times in the last few weeks but it recovered after I reboot the PC. However this trick doesn’t work any more. Connection to MySQL is fine still.

So, please help.

So what you’re testing there is the connection from the FactorySQL frontend to the service. Basically, FactorySQL runs in 2 parts: the service, which does all of the work, and the frontend, which connects to the service, where the configuration and all the graphical stuff is done.

Looks like you’ve probably accidentally changed something related to the connection to the service. That error message is the network telling your the port you specified isn’t open.

When the frontend isn’t connected to a service, all of the settings in the “settings” menu reflect the local system. Therefore, you can go to Settings->Service Settings to see what port the service is running on. The default is 5505. Back on the Connection Settings screen, change your connect to go to localhost and that port.

If you still can’t connect, let us know and we can go from there.


Following your instructions. The port was set as 6666 instead of 5505. So I just tried both. It shows a different warning with 5505: “Unable to Connect! Error verifying connection: No connection could be made because the target machine actively refused it”.


Ok… and you confirmed that 5505 is what was set under Service Settings?

Next things to check:

  1. It could be that the FactorySQL service just isn’t running. To check, go to Control Panel->Administrative Tools->Services, and look for “FactorySQL service”. Is it started? If not, go ahead and start it. If it is started, click stop… and then start. This will restart it, but my goal here is to make the next step easier…

  2. In the frontend, go to Help->Log Viewer. After a restart of the service, you should see 8 green check boxes. You may have to hit the refresh button a number of times, if you happen to be looking at it while the service is actually starting.

If there are any red Xs, click on them and post the pertinent details here, especially any error messages regarding starting the “remote communication system”.

If you get the green checks, try connecting again.

Finally, make sure windows firewall isn’t turned on and blocking the app. I know you said that it was previously working, but sometimes various windows updates can happen and turn things back on without any notification.

Hope this helps,

I checked the service, it was not running. I started it manually. I also turned off firewall and reboot the PC just in case. Now the error message changed to:“Error verifying connection: Tcp channel protocol violation: expecting preamble”.
And the error message in log viewer is here.


Ah, ok, so right now there’s some other application that already has that port open.

It could be the FactorySQL Tray Application, who will take over and run if the service isn’t started, or it could be a different application.

Try the following:

  1. Stop the FSQL service.

  2. Open Windows Task Manager (CTRL-ALT-Del, or right click on the task bar), go to “Processes”, make sure the “show processes from all users” is selected, and then sort the processes by name. End anything starting with “FactorySQL” (well, you don’t have to end the frontend, so basically any instances of “FactorySQL Tray Application.exe”)

  3. Restart the service. Check the error log- in this case it will probably be easier if you de-select both the “merge repeat events” and “group by category”. If you’re still getting that error (“only one use of port permitted”) then some other application is using 5505. If not, you should be good.

IF something else is using the port: In the FSQL frontend, go to Service Settings. Change the port to something else, like 5503. Make a similar change in your connection under “Connection Settings”. Restart the service. It should now be using the new port.

Hope this helps!

Great. After reboot PC, start and stop the service many times, the connection is established on port 5503. However, I can not see tags in the PLC still. Here is what I see now in FactorySQL front end.

Thanks a lot!

Normally in RSLinx there is a Topic node, under which there are “Online” and “Offline” nodes. Under “Online” you then find your processor’s memory space.

It looks like something may be wrong with your RSLinx topic setup. Is it possible that the device isn’t connected/is unavailable/isn’t there? I would go to Linx and see if it shows up as connected, and check the config in general.

Once connected, hit the “refresh OPC servers” button on the FactorySQL toolbar to refresh the server list. You should ultimately be able to browse down to “Online” and beyond to find your tags.

Hope this helps,

Hi Colby,
You are absolutily right. It’s all working now.

Thank you for the help.