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Version: 5.5

OPC-DA connections

We are currently not aware of any sources of error that restrict access to local OPC servers. However, accessing distributed OPC servers can present some pitfalls.

Connection cannot be established – remote only​

The "OPC Server" property returns <error browsing="" opc-servers="">.

Error Browsing OPC Servers

Check whether the DCOM configuration is correct:

  • Is the configuration environment running under the same user who has DCOM access to the OPC server?
  • Are both the OPC Enum and OPC Server components enabled for the user on the target computer?
  • Is DCOM enabled on the target computer in general?
  • Are the local firewalls on the computers involved disabled?
  • Of course, the target computer is turned on and accessible!

Connection is established, but the OPC connection does not appear in the OPC transfer object.​

The OPC server could be connected in the configuration, but the OPC connection does not appear in the connection project planning in the OPC transfer object, or an error is returned.

  • You must save the OPC connection using the "OK" button before it is available.

Tag browser cannot connect to the OPC server.​

If the OPC connection could be configured without any problems, check whether the OPC server has just been manually shut down or is being reinitialized.

  • Is the computer with the OPC server switched on and accessible?

No data transfer takes place at runtime​

The connection could be established without any problems at design time. No transfer takes place at runtime. Open the log file via the tray icon. Look for the error message at the end of the file. Does the error message look like this?

16.07.16 14:49:06.194 [Error:OPCConnectionManager] 
   The item <item\> could not be registered (E_INVALID_ITEM_NAME)
  • You have probably spelled the item name incorrectly, or your OPC server is not evaluating the Access Path property stored in the OPC connection correctly. Select the item using the tag browser and/or configure a connection without Access Path for testing purposes. Check whether your OPC server is running correctly.

Error message in log file:

07/16/16 3:19:34.886 p.m. [Error:NoChannel] Timeout connect OPC Server!
  • In distributed systems: Is the computer with the OPC server turned on and accessible?

Error message in log file:

07/16/16 3:16:24.694 p.m. [Error:OPCConnectionManager] The connection to the OPC server
    <opc-server\>at <ip\> could not be established.
  (Message: CoCreateInstanceEx: Access denied)
  • If the connection works during design time, the router configuration is probably running under the correct user, but the router service is not. Check whether the router service running under the user has DCOM permission on the OPC computer.