---
title: "FAQ"
description: "Frequently asked questions about the Data Layer of the LumiScan apps - platforms, broker, addresses, handshake, execute, streams, status codes and OPC UA."
product: "LumiScan Keryx"
component: "lumiscan-keryx"
version: "1.0.0"
display_version: "1.0.0.7"
latest_version: true
language: "en"
url: "https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/faq.html"
---

# FAQ – LumiScan Keryx

Short answers to common questions about the Data Layer. Each entry links to the page with the details. Problems and error messages are described in [Troubleshooting](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html).

> [!TIP]
> Each entry has a fixed anchor (for example `#faq-start-broker`). To find an error message, search the [Troubleshooting](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html) page for it.

## Platforms and broker

### Do I have to change my program when I move from ctrlX OS to a PC? {#faq-same-interface}

- **Answer:** No, not the node addresses, types or call patterns: they are the same on the ctrlX Data Layer and LumiScan Keryx. What changes is the connection (a PLC on ctrlX OS, the OPC UA Connector on a PC), the tools, and the names of the method results.
- **More:** [ctrlX Data Layer and LumiScan Keryx](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/platforms.html)

### Do I have to start the broker on a PC? {#faq-start-broker}

- **Answer:** No. When an app starts and no broker answers on the PC, it starts one at `tcp://127.0.0.1:5555`. The broker keeps running when the apps end. Only the OPC UA Connector never starts one: start it after the apps.
- **More:** [The broker](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/keryx.html#broker)

### How do I look at the nodes? {#faq-see-nodes}

- **Answer:** On Windows on the Keryx page `http://127.0.0.1:7555/`, in **LumiScan Keryx Utilities**, or with `krxclient`. On Ubuntu with `krxclient`. On ctrlX OS in the Data Layer view of the ctrlX OS web interface.
- **More:** [Tools](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/tools.html)

## Calling functions

### Should I use the handshake or the execute method? {#faq-handshake-or-execute}

- **Answer:** Use the execute method for operations within about 1 s when your program can wait. Use the handshake for longer operations - the Cam Driver’s `connect-camera`, `disconnect-camera` and `reset` are handshakes only - or when your program must not block. Use a stream for continuous processing.
- **More:** [Choosing a Pattern](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/calling-functions.html)

## Streams

### How does a PLC read stream results? {#faq-stream-plc}

- **Answer:** Stream results are FlatBuffers records. Switch on `keep-latest-output` in the module whose result you need and read its plain output nodes, or subscribe to Calibration’s `plain-points`.
- **More:** [Keep latest output](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/streams.html#keep-latest)

## OPC UA

### Can the OPC UA Connector use encryption or user names? {#faq-opcua-security}

- **Answer:** No. It accepts anonymous, unencrypted clients only. Run it on a trusted machine network, open port 4840 for the PLC only, and give observing clients a `--read-only` instance.
- **More:** [Security](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/opc-ua.html#security)

## Troubleshooting {#troubleshooting}

Problems and error messages are described step by step in [Troubleshooting](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html):

- [An app waits for the broker (PC)](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#no-broker)
- [An app or a module is missing from the tree](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#app-missing)
- [A node is "not found"](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#node-not-found)
- [A method call is refused](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#refused)
- [Status `-5` (`restartRequired`), or `ResourceUnavailable` on every call](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#faq-restart-required)
- [The execute call answers `Ok` (`DL_OK`), but nothing happened](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#faq-write-ok-but-failed)
- [A handshake does not finish, or shows the wrong outcome](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#handshake-stuck)
- [A stream delivers nothing](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#stream-nothing)
- [Stream results are old or mixed](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#ts-stream-results-mixed)
- [An OPC UA client cannot connect](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#ts-opcua-cannot-connect)
- [The connector window closes at once](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#ts-opcua-window-closes)
- [`Objects` is empty or has no `hdvisionsystems`](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#ts-opcua-objects-empty)
- [`BadNodeIdUnknown`](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#ts-opcua-bad-node-id)
- [`BadTypeMismatch` on a write](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#faq-opcua-type-mismatch)
- [A subscription gets only one value, or misses results](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#ts-opcua-subscription)
- [Notifications stop after the connector or an app restarts](https://docs.hdvisionsystems.com/en/lumiscan-keryx/1.0.0/troubleshooting.html#ts-opcua-notifications-stop)

## Support

### Where do I get help? {#faq-support}

- **Answer:** See the site-wide [LumiScan FAQ](https://docs.hdvisionsystems.com/en/faq.html), or contact [customer.success@hdvisionsystems.com](mailto:customer.success@hdvisionsystems.com), +49 6221 6721905. For licences: [licenses@hdvisionsystems.com](mailto:licenses@hdvisionsystems.com).