OPC UA connections
If an OPC UA client connection fails to establish or if data points remain without a valid value, check the following points. If the flow does not reach the transfer stage at all, first follow the steps in “” (“Transfer Does Not Run”) .
This page applies to OPC UA. Troubleshooting for OPC Classic (OPC DA) can be found at OPC Classic Connections ; the topics covered there—DCOM configuration, item names, and service permissions—do not apply to OPC UA.
Check the connection
The OPC UA connection includes its own test: In the plug-in configuration, use the “Check connection” button to establish an initial connection.
The test is successful only if the same security level is set on both sides and all other prerequisites are met—for example, that the client and server certificates to be exchanged are classified as trusted. See OPC UA .
The endpoint is accessed via its IP address
When using certificates, the endpoint must be addressed exactly as specified in the certificate. For example, if the certificate lists Server.domain.local, the connection must not be established via the IP address—otherwise, the OPC server’s certificate will be rejected. See Connection.
The server certificate is not accepted
In the "" tab under "Security" (), you can specify which server certificates the OPC Router trusts: all, only those maintained in the OPC Router, or only those from the Windows certificate store. This section also specifies whether the server certificate’s validity is checked and whether the server’s application URI is validated against the configured URI.
If certificate validation is disabled, the OPC Router no longer checks the server certificate for validity—even incorrect server names and expired certificates are then accepted.
If the router obtains its certificates from a Global Discovery Server, the server’s own states are also taken into account—see OPC UA GDS .
The connection is established, but data points are not returning any usable values
OPC UA reports a status code for each data point. Among other things, it distinguishes whether the node is unknown to the server, there is no connection to the data source, initial values are not yet available, or authorization is missing. The typical codes and their meanings can be found at Typical Status Codes .
If not all expected data points are displayed in the tag browser, check the connection’s access path: If it is set, the browser will display only the data points from the selected folder.
The connection unexpectedly switches servers
If a redundant server is configured, the connection automatically switches to it if the primary server is unavailable or—if configured—if the primary server’s lifetime cannot be read or returns the value “0.” See Redundancy .