OPC UA troubleshooting

Narrow down the cause

Find the step that failed. The examples’ error texts start with the step: discover failed, connect failed, activate failed, read failed. Failures during discovery are address, port or path problems; failures while connecting are usually security and certificate problems.
Tell the kind of error. Is it a C ABI status, an OPC UA StatusCode or a security error name? Look it up in the StatusCode catalog.
Separate the service result from item results. As in service=0x00000000 status=0x803b0000, the service can succeed while one item fails.
Reproduce the case with the simulator. Its action record and the server’s audit record show which side refused; see Timeouts and diagnostics.

Error text	Cause and fix
`OPC UA I/O: connection refused (os error 61)`	The server isn’t running, or the port differs. The error number depends on the operating system.
`OPC UA status: 0x80830000`	The endpoint URL path doesn’t match the server (BadTcpEndpointUrlInvalid).
`Requested OPC UA endpoint not advertised`	The server doesn’t advertise the requested security policy and mode; pick a combination from the discovery result.
`OPC UA security CertificateUntrusted`	The client doesn’t trust the server certificate; see Certificate problems.
`OPC UA status: 0x80130000`	The server doesn’t trust the client certificate (BadSecurityChecksFailed).
`OPC UA security CertificateHostInvalid`	The server certificate doesn’t contain the URL’s host name.
`OPC UA security CertificateUriInvalid`	The certificate’s URI differs from the ApplicationUri.
`OPC UA status BadUserAccessDenied (0x801F0000)`	The user name or password is wrong, or repeated failures locked the client out.
`status=0x801f0000`	An anonymous session accessed a variable for authenticated users only.
`status=0x803b0000`	A write to a read-only variable (BadNotWritable).
`status=0x80340000`	The node doesn’t exist (BadNodeIdUnknown).
`OPC UA timeout`, `Timeout (client connection closed)`	No response arrived within the timeout.
`create failed (SDK status 5): OPC UA I/O: address in use (os error 48)`	Another process uses the server’s listen address; use another port or stop that process.

Error	Cause and fix
CMake `Set PDCOMM_OPCUA_SDK to the extracted SDK root`	The examples couldn’t find the SDK; pass `-DPDCOMM_OPCUA_SDK=<SDK root>`.
CMake `This SDK profile does not contain the Qt helper`	You turned on the Qt example in the `native` package, which has no Qt helper; use the `qt` package.
.NET `Set PdcommOpcUaSdk to the extracted PDComm OPC UA SDK root.`	The `-p:PdcommOpcUaSdk` path is wrong.