---
title: "OPC UA Server | Configuration | N3uron KB V1.22"
slug: "opc-ua-server-configuration"
description: "OPC UA Server is a N3uron module designed to expose the data collected through any other data acquisition module within the platform to third-party systems…"
updated: 2026-08-05T12:23:09Z
published: 2026-08-05T12:23:09Z
canonical: "docs.n3uron.com/opc-ua-server-configuration"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.n3uron.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Configuration

> [!NOTE]
> **Note:**
> 
> Before starting configuration, a new module instance must first be created. [**Click here for more information about creating Module instances**](/v122/docs/platform-create-new-module-instance).

## Module Configuration

Once a new **OPC UA Server** module instance is created, users can configure different parameters to establish how connections to the server should be made. Below you will find a brief explanation of what each of these parameters mean and how to configure them:

| **Setting** | **Description** |
| --- | --- |
| Network interface | Specifies which network interface cards will be permitted for incoming connections. For example: - **127.0.0.1** or **localhost** only allows connections from local applications. - It's also possible to select the network interface by either entering its specific IP address or clicking on the button to the right of the **Network interface** field. |
| TCP Port | Specifies the port number for incoming connections. The valid range is **1** to **65535**. The default value is **3005**. > [!NOTE] > **Note:** > > Make sure that the port number is not used by any other application. |
| Alternate host | Specifies one or more alternate hosts to use during the initial handshake as a comma-separated list of hosts. Usually, the public IP address is used if the server is behind a firewall to avoid authentication problems for the client. |
| Allow anonymous user | When set to **True**, users can login anonymously with all permissions. |
| Disable discovery | Enables or disables discovery for this endpoint. The default value is **Disabled**. |
| Security policies | Specifies which security mechanism should be used. Supported algorithms are as follows: - **None** - **Basic 128 & Rsa 15** (deprecated since **OPC UA Specification Version 1.04**) - **Basic 256** (deprecated since **OPC UA Specification Version 1.04**) - **Basic 256 & Sha 256** |

### **Server**

| **Setting** | **Description** |
| --- | --- |
| Separator | Specifies which character will act as a separator for tag names. The default is "**.**". |
| Maximum number of connections | Maximum number of connections per endpoint. The default value is **20**. |
| Include tag properties | Determines whether to include tag properties (such as full path, source name, engineering units, etc.) as part of the address space. The default value is **Disabled**. > [!NOTE] > **Note:** > > When enabled, the RAM usage of the module will increase substantially. |

### **Server capabilities**

| **Setting** | **Description** |
| --- | --- |
| Maximum number of sessions | Maximum number of active sessions in the server. The default value is **20**. |
| Minimum supported sample rate | Minimum sampling rate for tag events that the server will support, displayed in milliseconds. The default value is **500ms**. |

### **Store & Forward**

| **Setting** | **Description** |
| --- | --- |
| Enabled | When **Enabled**, all data flowing from remote nodes via [**Links**](/v122/docs/platform-links) will be halted and data will be stored in the remote nodes whenever there are no active OPC Clients consuming this data. As soon as at least one OPC Client starts consuming data from a remote node, the data flow from this node will be resumed. > [!NOTE] > **Note:** > > If **Store & Forward** is enabled and there are no OPC Clients currently consuming data, Store & Forward mode will be activated and data values coming from remote nodes will not be updated. |
| Buffer size | Defines the maximum number of events to store before sending a halt command to the source link. The default value is **100**. |

> [!WARNING]
> **IMPORTANT:**
> 
> **Store & Forward** should **only** be **enabled when** the **OPC UA client** **consumes all events received** **through the Link**. Do not use Store & Forward on the OPC UA Server if the client is subscribed to only a subset of the available tags.

![](https://cdn.document360.io/54093ab5-6b22-4542-a265-04377931f11a/Images/Documentation/image(221).png)

### **Additional endpoints**

**Additional endpoints** lets you expose the OPC UA Server through more than one listening endpoint, each with its own network binding and security configuration. This is useful when the same server needs to be reached over different network interfaces or ports — for example, an insecure endpoint on localhost for local tools and a secured endpoint on a public interface for remote clients — without running a second module instance.

To add one, click on the button to the right of **Additional endpoints** and select **New Endpoint**. Each endpoint is configured independently and offers the same connection parameters as the main endpoint:

| **Setting** | **Description** |
| --- | --- |
| Network interface | Specifies the network interface card permitted for incoming connections on this endpoint. Enter **0.0.0.0** to listen on all interfaces, or a specific IP address. The default value is **0.0.0.0**. |
| TCP port | Specifies the port number for incoming connections on this endpoint. The valid range is **1** to **65535**. > [!NOTE] > **Note:** > > Each endpoint must use a port that is not already in use by another application or by another endpoint of this module. |
| Alternate host | Specifies one or more alternate hosts to use during the initial handshake as a comma-separated list of hosts. Usually, the public IP address is used if the server is behind a firewall to avoid authentication problems for the client. |
| Allow anonymous user | When set to **True**, clients can connect to this endpoint anonymously with all permissions. |
| Disable discovery | Enables or disables discovery for this endpoint. The default value is **Disabled**. |
| Security policies | Specifies which security mechanisms are accepted on this endpoint. Each policy is independently set to a security mode (**None**, **Sign**, or **Sign & Encrypt**). Supported algorithms are as follows: - **None** - **Basic 128 & Rsa 15** (deprecated since **OPC UA Specification Version 1.04**) - **Basic 256** (deprecated since **OPC UA Specification Version 1.04**) - **Basic 256 & Sha 256** |

## Access

In this area, you will assign the corresponding permissions to the Roles previously created in the [**Roles**](/v122/docs/platform-security-users-and-roles) section.

![OPC UA Server Access permissions](https://cdn.document360.io/54093ab5-6b22-4542-a265-04377931f11a/Images/Documentation/Figure%203%20-%20Access%202.png)

Parameters:

| **Setting** | **Description** |
| --- | --- |
| Enabled | Specifies whether or not an authentication attempt will be blocked. |

### **Node permissions**

| **Setting** | **Description** |
| --- | --- |
| Browse | Enables browsing of the _Node object. |
| Read role permissions | Allows reading of role permissions in the _Node object. |
| Write attribute | Allows attributes to be written in the _Node object. |
| Read | Allows reading of values in the _Node object. |
| Write | Allows values to be written in the _Node object. |
| Read history | Allows reading of historic values in the _Node object. |
| Receive events | Allows node events to be received from the _Node object. |
| Call method | Allows calling of node methods in the _Node object. |

### **Tag permissions**

| **Setting** | **Description** |
| --- | --- |
| Browse | Allows tag browsing. |
| Read role permissions | Allows reading of tag role permissions. |
| Write attribute | Allows attributes to be written to tags. |
| Read | Allows reading of tag values. |
| Write | Allows writing of tag values. |
| Read history | Allows reading of tag history. |
| Receive events | Allows OPCUA events to be received from tag objects. |
| Call method | Allows calling of tag methods. |

### **Tag access**

> [!WARNING]
> **Note:**
> 
> It is mandatory to add a filter even when the whole model is going to be exposed.

| **Setting** | **Description** |
| --- | --- |
| Mode | Selects whether the filter must include or exclude tags. > [!NOTE] > **Note:** > > Include filters are applied first and exclude filters are applied to the result of the include filters. |
| Path | Specifies the path of the tag or group of tags to be filtered. |
| Regex pattern | This is a regular expression for filtering which tags will be included. By default, it is set to **.***, which means that no filter is applied. Readers can find further information about regular expressions at [RegExr](https://regexr.com/). |

## Certificates

Once the module is running, whenever a client connects with a secure connection (different from **None/None**), the server will receive the client's certificate. By default, any certificate received is **Rejected** in **N3uron** and therefore, must be manually trusted in order to be able to establish the connection. For those clients that by default reject certificates sent by the server, manual approval of the certificate on the client side will also be necessary.

![Trusting an OPC UA client certificate in N3uron](https://cdn.document360.io/54093ab5-6b22-4542-a265-04377931f11a/Images/Documentation/Figure%207.2%20-%20Trust.png)

## Methods

The OPC UA Server module allows users to define methods along with their input and output arguments. These methods enable users to execute custom logic in the **N3uron** node by calling a script previously created in [**Scripting**](/v122/docs/scripting-introduction). Each method can have zero or more input and output parameters, which support a variety of data types and value ranks. When a method is defined, it will be available in the **_Node/Methods/METHOD_NAME** node of the OPC UA **Address Space**.

> [!NOTE]
> **Note:**
> 
> In order to use Methods, it is necessary to run both a **Scripting** module and at least one external script that will be invoked by the method.

> [!NOTE]
> **Note:**
> 
> The return value of the script has to be an object whose keys are the names of the output arguments and its values are the output values. The value type must be coherent with the OPC UA types declared in the method definition.

### **Creating a method**

To create a new method, expand the **OPC UA Server** module instance menu and select **Methods**. From the **Model** panel burger menu, select **New Method**.

**N3uron version <1.22.4**

![Creating a new method in the OPC UA Server module](https://cdn.document360.io/54093ab5-6b22-4542-a265-04377931f11a/Images/Documentation/Figure%20-%20Method%201.png)

**N3uron version >=1.22.4** ![](https://cdn.document360.io/54093ab5-6b22-4542-a265-04377931f11a/Images/Documentation/image(223).png)

The method configuration settings contain the following options:

| **Setting** | **Description** |
| --- | --- |
| Enabled | Enables and disables the corresponding method. |
| Scripting instance | Selects the corresponding **Scripting** module instance, which contains the script that will be executed when the method is called. |
| Script name | Name of the script that will be executed when the method is called. It is possible to either enter the path manually or click on the button to the right of the **Script name** field and use the browser to select it, providing that the Scripting module instance is running. |
| Description | Method description. |

**N3uron version <1.22.4**

![Method configuration settings](https://cdn.document360.io/54093ab5-6b22-4542-a265-04377931f11a/Images/Documentation/Figure%20-%20Method%202.png)

![Selecting the script for a method](https://cdn.document360.io/54093ab5-6b22-4542-a265-04377931f11a/Images/Documentation/Figure%20-%20Method%203.png)

Once the corresponding script has been selected, the **Input** and **Output arguments** can be created if necessary. To do this, click either on the buttons to the right of **Input arguments** or **Output arguments** to add them, enter a description if you like, and select the corresponding settings for both the **Data type** and the **Value rank** fields.

![Method Input arguments configuration](https://cdn.document360.io/54093ab5-6b22-4542-a265-04377931f11a/Images/Documentation/Figure%20-%20Input%20arguments.png)

![Method Output arguments configuration](https://cdn.document360.io/54093ab5-6b22-4542-a265-04377931f11a/Images/Documentation/Figure%20-%20Output%20arguments.png)

> [!WARNING]
> **Note:**
> 
> The **Method** group (**Module instance** and **Method name**) is available from **N3uron** version **1.22.4**. It generalizes the previous **Scripting instance** and **Script name** fields so that a method can target any compatible module instance. Existing method configurations remain fully compatible.

From version **1.22.4**, the target method is configured under a **Method** group with the following fields:

| **Setting** | **Description** |
| --- | --- |
| Module instance | Selects the target module instance that contains the method that will be invoked. |
| Method name | Name of the method that will be invoked when this OPC UA method is called. |

The **Input** and **Outputs** arguments each expose a **Description**, a **Data type** (for example **JSON String**), and a **Value rank** (for example **Scalar**).

**N3uron version >=1.22.4** ![](https://cdn.document360.io/54093ab5-6b22-4542-a265-04377931f11a/Images/Documentation/image(224).png)

### **Method groups**

> [!WARNING]
> **Note:**
> 
> Method groups are available from **N3uron** version **1.22.4**.

Methods can be organized into **method groups** (folders). Method groups let you group related methods together, creating a more organized and navigable method hierarchy within the OPC UA **Address Space**. To create one, expand the **Methods** menu in the **Model** panel and select **New MethodGroup**. Methods created inside a group are exposed under the corresponding folder in the **_Node/Methods** node.

### **Browse methods**

> [!WARNING]
> **Note:**
> 
> The **Browse methods** action is available from **N3uron** version **1.22.4**.

The **Browse methods** action lets you discover and inspect the methods available in this node and automatically create the corresponding OPC UA method definitions, instead of adding each one manually. Expand the **Methods** menu in the **Model** panel and select **Browse methods** to open the **Select methods** dialog.

> [!NOTE]
> **Note:**
> 
> For a script to appear in the **Select methods** dialog, the **Scripting** module instance must expose it as a named method. From **N3uron** version **1.22.4**, external scripts in the **Scripting** module are exposed as named **Methods**: in the script Task, add an Action and set its **Type** to **Method** (**Actions → Type → Method**). Each script in that Task is then published as a named method (for example, **ops_summary_daily** or **system_audit_node**) that can be browsed and imported here.

![](https://cdn.document360.io/54093ab5-6b22-4542-a265-04377931f11a/Images/Documentation/gifMethodOpc.gif)

In the **Select methods** dialog, the methods exposed by the running **Scripting** module instances are listed and organized by their group hierarchy. Select the check box next to each method you want to expose; the right-hand panel shows the selected method's details, including its **Write** flag and its **Input** and **Output** types. Click **Apply** to automatically create a method definition for each selected method.

> [!WARNING]
> **Note:**
> 
> Browse methods auto-creation handles the full **Scripting** type matrix, so all supported input and output argument types are correctly mapped when the methods are automatically generated.

Each generated method keeps the same group hierarchy it had in the **Scripting** module and is created with its **Module instance**, **Method name**, and **Input** and **Output** arguments already populated with the correct **Data type** and **Value rank**. After applying, remember to **Save** the configuration.

[Embedded content](https://www.youtube.com/embed/YVsQgRDs524)