Connect IoT - OPC UA Driver#

OPC Unified Architecture (OPC UA) is a machine to machine communication protocol for industrial automation developed by the OPC Foundation. Distinguishing characteristics are:

• Focus on communicating with industrial equipment and systems for data collection and control
• Open - freely available and implementable without restrictions or fees
• Cross-platform - not tied to one operating system or programming language
• Service-oriented architecture (SOA)
• Robust security

Data Types#

These are the supported specific data types:

Table: OPC UA specific data types

Protocol Parameters#

The protocol supports the following parameters:

Table: OPC UA specific parameters

Extended Parameters#

As with other protocol drivers, some extra parameters are necessary to provide more context to the behavior expected.

Property#

Event#

EventProperty#

Command#

Command Parameter#

Driver Extensions#

This protocol driver provides a set of extension that allow the customization to perform actions that are independent of the Driver Definitions associated. This means you can, using customization, get/set node values without needing to describe them.

• This is particularly useful when accessing equipment data that is shared/too complex to access using the regular mechanisms. Also useful when needing to access data whose naming convention may vary from device to device.
• To use these extensions you can either implement your own task or use the supplied Tasks Send Notification to Driver and Subscribe in Driver.

Objects#

The objects are structures that are either passed as parameters or returned as result values.

Event#

Property#

PropertyValue#

PropertyValuePair#

RegisterHandler#

UnregisterHandler#

Methods#

Get Properties Values#

Requests the server for the values of one or more properties (Nodes/Tags)

PropertyValue[] connect.iot.driver.opcua.getPropertiesValues(request Property[])

Example#

Request connect.iot.driver.opcua.getPropertiesValues

[
  {
    "name": "stringValue",
    "deviceId": "ns=2;s=Demo.Static.Scalar.String",
    "originalValue": "String"
  },
  {
    "name": "integerValue",
    "deviceId": "ns=2;s=Demo.Static.Scalar.Int16",
    "dataType": "Integer"
  }
]

Reply:

[
  {
    "propertyName": "stringValue",
    "originalValue": {
      "dataType": "String",
      "arrayType": "Scalar",
      "value": "Hello World",
    },
    "value": "Hello World",
  },
  {
    "propertyName": "integerValue",
    "originalValue": {
      "dataType": "Int16",
      "arrayType": "Scalar",
      "value": 123,
    },
    "value": 123,
  }
]

Set Property Values#

Requests the server to define the values of one or more properties (Nodes/Tags).

boolean connect.iot.driver.opcua.setPropertiesValues(request PropertyValuePair[])

Example#

Request connect.iot.driver.opcua.setPropertiesValues

[
  {
    "property": {
      "name": "stringValue",
      "deviceId": "ns=2;s=Demo.Static.Scalar.String",
      "deviceType": "String"
    },
    "value": "Hello World"
  },
  {
    "property": {
      "name": "integerValue",
      "deviceId": "ns=2;s=Demo.Static.Scalar.Int16",
      "deviceType": "Int16"
    },
    "value": 123
  }
]

Reply:

true

Register Event#

Notifies the protocol driver to raise the occurrences of a specific event when it occurs.

void connect.iot.driver.opcua.registerEvent(data: RegisterHandler)

Example#

{
   "event":{
      "name":"CustomEvent",
      "isEnabled":true,
      "properties":[
         {
            "name":"humidity",
            "deviceId":"ns=2;s=Demo.Static.Scalar.Double",
            "dataType":"Decimal",
            "deviceType":"Double",
            "extendedData":{
               "isTrigger":true
            }
         }
      ]
   }
}

Unregister Event#

Notifies the protocol driver to stop raising the occurrences of a specific event when they occur.

void connect.iot.driver.opcua.unregisterEvent(data: UnregisterHandler)

Example#

{
   "event":{
      "name":"CustomEvent"
   }
}

Send Command#

Will be implemented in a future version.

Remarks/Behavior#

• When an event has more than one property with the isTrigger flag:
  • It will be triggered every time any of the properties value changes.
  • The value of the other properties will be requested at that time.
  • It is possible to have multiple triggers with the same set values (because they have not changed). If this behavior is not intended, separate into multiple events each one with it's own trigger set.
• When an event has no property with the isTrigger flag, it will never be triggered.
• When using events of type Event the property device id must follow the format <Namespace>:<name> (ex: 2:Temperature)
• When it´s necessary to convert a value from Int64/UInt64 to Long, Integer or Decimal, a warning is displayed stating that a conversion was made on the value, that could cause a loss in the accuracy. When the accurate value is needed, the RawValue should be used to be processed.
• To store OPC UA certificates (trusted, rejected, and own) in a custom location, set the NODEOPCUA_PKI environment variable. This overrides the default directory and ensures the driver uses a consistent PKI path across all environments.
  • Example: export NODEOPCUA_PKI=/opt/iot/opcua-pki

Transparent Redundancy#

This driver only supports transparent redundancy.

In transparent redundancy, failover between servers is invisible to the client. If a server becomes unavailable, the client is not notified and does not need to take any action.

Servers in a transparent redundancy group appear as a single OPC UA server. They typically share the same Server URI and Endpoint URL, often exposed through a virtual IP address or a network load balancer. From the client’s perspective, there is only one server connection, and no special failover logic is required.

Failover is handled by the underlying infrastructure or cluster. When the primary server fails, the system automatically directs client communications to a standby server, allowing data exchange to continue without interruption.

Because this approach shifts complexity to the server and network layers, it requires a robust clustering setup. This usually includes a virtual IP address or network load balancer in front of multiple servers, as well as mechanisms to keep servers’ state in sync.