--- title: Troubleshooting OPC-UA connections slug: how-tos/Rou3-troubleshooting-opc-ua-connections docTags: UDglSYuzCeqYsFuKMx-fS createdAt: 2025-09-01T12:17:30.147Z --- ## Common connection issues | Error | What it Means | How to Fix | | ------------------------------------------------ | ------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------- | | TCP connection timeout or TCP connection refused | Network/firewall issue | Check network path and firewall.
Windows: `test-netconnection -port `
Linux: `telnet ` | | TCP connection refused | OPC-UA server not listening on this address/port | Verify the address and port in the OPC-UA server settings and/or check the logs of the OPC-UA server | | StatusBadTCPEndpointURLInvalid (0x80830000) | Wrong endpoint address | Check and correct the endpoint in server vs. client | | Failed to find suitable endpoint | Security settings mismatch | Adjust SecurityMode/Policy in client or server | | StatusBadIdentityTokenInvalid (0x80200000) | Wrong username/password or credentials not needed | Enter correct credentials, or remove them if not needed | | EOF / BadSecurityChecksFailed (0x80130000) | Certificate not accepted yet | Accept the client certificate on the server | | Unstable (collector health) | Multiple consecutive read requests failed | Check the specific issue in the collector logs | ## Other connection issues - **Time difference:** If clocks are too much out of sync (hours, not seconds), security tokens may expire too soon. Sync all clocks with NTP. ## Common OPC-UA status codes When collecting data from an OPC-UA server, each value comes with a status code that tells you if the data is reliable (Good) or if there is a problem with it. Here are some common status codes and what they mean. | Status Code | Meaning | What to Do | | ---------------------------------------------------------- | ---------------------------------------------------------------- | -------------------------------------------------------------------------------------------- | | Bad (0x80000000) | Unspecified issue with the data | Check the data at the source | | BadNodeIDUnknown (0x80340000) | The NodeID is unknown to the server | Browse the server to find the correct NodeID | | BadNodeIDUnknown (0x80340000), but only for monitored data | The namespace is incorrect | Try another namespace, e.g. ns=2 instead of ns=3 or vice versa | | BadTooManyOperations (0x80100000) | Too many operations in one request | Lower the `MaxNodesPerRegister` and/or `MaxNodesPerRead` setting | | BadTooManyMonitoredItems (0x80DB0000) | Too many monitored items for the server | Adjust server limits or split over multiple collectors
Sometimes: clean up old sessions | | GoodOverload (0x002F0000) | Server can't keep up with requested rate | Lower the update rate or increase server resources | | BadTimeout (0x800A0000) | Server couldn't provide a value in time | Check network, device status and server resources | | BadNothingToDo (0x800F0000) | Client requested an action that does not change anything (no-op) | Nothing | | BadOutOfMemory (0x80030000) | Server cannot complete the request due to RAM limitations | Lower the update rate or increase server resources | For a full list of OPC-UA status codes, see the [official list](https://github.com/OPCFoundation/UA-Nodeset/blob/latest/Schema/StatusCode.csv). ## Factry status codes Factry has added a few of our own status codes to highlight specific issues. | Status Code | Meaning | What to Do | | -------------------------------------------------------------------- | ----------------------------------------------------------- | ---------------------------------------------------------------- | | BadInvalidNodeID | The NodeID in your settings contains syntax errors | Enter a valid NodeID | | BadFactryOPCUARegisterNodesFailed | Collector failed to register nodes (often too many at once) | Lower the `MaxNodesPerRegister` and/or `MaxNodesPerRead` setting | | BadFactryMonitorError / Error from subscription notification channel | Collector failed to monitor nodes (often too many at once) | Lower the `MaxNodesPerMonitor` setting | | BadNoValueAtArrayIndex | Array index out of bounds or missing value | Check the `ArrayIndex` setting | | BadFactryOPCUATooManyOpenReadRequests | New read requests open faster than they are processed | Check network, device status and server resources | | UnknownStatusCode\_0xXXX | Status code outside OPC-UA spec | Check server docs | | BadFactryInvalidDataForDatatype | Data can't be parsed to the requested type | Check the `Datatype` setting | ## Other data collection issues ### Value for monitored measurement after reconnect Whether monitored measurements receive a value after a reconnect depends on the implementation of the OPC-UA server. There are 3 options: - The server does not send a value - The server sends the latest value with its original timestamp - The server sends the latest value with the current timestamp Depending on the behavior, a monitored measurement can keep a bad quality for a while after reconnect. Since the quality is only updated when points come in, the bad quality will remain until new Good data arrives. ### x509: invalid basic constraints The log `Error attempting to reconnect to OPC-UA server: x509: invalid basic constraints`indicates that the OPC-UA server certificate is not valid. Update the collector to [v2.0.3](https://docs.factry.io/changelog/opc-ua-collector#v203) or higher or contact your OPC-UA server vendor to update the server certificate to a valid one if the issue persists. ### Kepware For issues specific to Kepware, have a look at [Kepware troubleshooting](docId\:B5Nu0JEkqROHMcG7xfU3C). ### Low-level debugging If necessary, low-level OPC-UA logging can be enabled to debug connection issues. To do so, set the [LogLevel](docId\:im-7Bhp1Lmte9WPvndn_Y) to 'trace'. If that option is not available, [update the collector](docId\:g3adOd9UPOm4AlSlqULWR) to [v2.1.0](https://docs.factry.io/changelog/opc-ua-collector#v210) or higher or follow the steps described [here](docId\:HCpRRBDF014CY4o9r3w1i).