AlOPCUAServer
Overview
AlOPCUAServer is a process, that can be implemented on Windows or embedded in a target with Windows or Linux operating system.
Every server can connect to many PLC runtimes and can publish all the symbols defined by the PLC application.
It can be accessed from the server IP, with default port 48020.
Configuration: Server Side
The configuration of the OPCUA Server can be done with the simple configuration XML AlOPCUAServer.conf, here an example:
<?xml version="1.0"?>
<opcuacfg>
<instance
name="PLC Local"
protocol="gdb"
params="127.0.0.1:5000"
maxArrayElems="10"
maxMatrixElems="5"
/>
<instance
name="PLC Remote"
protocol="gdb"
params="10.0.0.91:5000"
maxArrayElems="10"
maxMatrixElems="5"
/>
</opcuacfg>
This simple configuration file specifies the server to connect to two PLC runtimes, with protocol GDB, that is Axel's default.
The field name specifies the name of the root node for that PLC in the OPCUA namespace.
The field params specifies protocol specific params: in this example the TCP/IP and Port on which runtimes are listening for the GDB connections.
The last two fields maxArrayElems and maxMatrixElems are constraints about automatic array and matrix expansions feature:
under any array or matrix node, in the OPCUA namespace, the server will publish a node for each element of the array.
These two constraints limits the amount of elements that are automatically created.
Configuration: LogicLab side
To configure the OPCUA server within LogicLab, navigate to the Resources tool window and locate the OPCUA Server node. Within this server configuration, you will find a branch specifically named Allowed Symbols. This section plays a critical role in data visibility and security: while an unconfigured or empty list might leave all defined project symbols completely transparent to an OPCUA client, the Allowed Symbols branch allows you to selectively filter and explicitly define which specific variables are exposed and accessible for external client communication.
The Enable Allow List setting serves as a vital security and filtering switch for your OPCUA server configuration. By toggling this field to enabled, you activate a strict access rule: instead of exposing every single variable in your project to external clients by default, the server restricts access and only shares data that has been explicitly approved. This gives you complete control over your automation system's data privacy, ensuring that internal diagnostic tags or sensitive process parameters remain safely hidden from external networks.
Once the allow list is active, you can use the Add and Remove management options to handpick the exact variables you want to share. Through this interface, you can select PLC Type as individual Variable or Variable Group to be published from your PLC application to any connected OPCUA client. This capability allows external monitoring software to safely and efficiently read only the operational data they actually need, keeping your communication network clean, organized, and secure.
If you select Variable as your target type, the configuration interface simplifies your workflow by providing a direct dropdown menu in the Name field. Instead of manually typing out complex variable paths, you can simply choose the exact tag you need straight from a comprehensive list of all active variables available in your project, which helps prevent spelling errors and broken references.
Alternatively, if you select Variable Group as your type, the system allows you to choose from pre-defined groups that you have already organized within your PLC project. This is an efficient approach for structured programming, as it enables you to bundle related data such as all status flags or recipe parameters for a specific machine station, into a single logical set and publish the entire block together, keeping your OPCUA mapping clean and easy to maintain.