OPC UA

Connection String Options

Name Value Description

Code

opcua

Name

OPC UA

Maven Dependency

<dependency>
  <groupId>org.apache.plc4x</groupId>
  <artifactId>plc4j-driver-opcua</artifactId>
  <version>{current-last-released-version}</version>
</dependency>

Default Transport:

 tcp

Compatible Transports:

  • tcp (Default Port: 4840)

Supported Operations

read

The read interface allows for reading the full range of supported PLC4X data types in single and bulk requests

write

The write interface allows for writing the full range of supported PLC4X data types in single and bulk requests

subscribe

Subscriptions are possible with events on event- and cyclic-basis

Options

discovery

Controls the feature of the discovery endpoint of an OPC UA server which every server will propagate over an '<address>/discovery' endpoint. The most common issue here is that most servers are not correctly configured and propagate the wrong external IP or URL address. If that is the case you can disable the discovery by configuring it with a false value.

Connection String

The OPC UA drivers uses the connection string

opcua:{transport}://{ip-address}:{port}?{options}

An example of this connection string would be:-

opcua:tcp://127.0.0.1:12686?discovery=true

Note the transport, port and options fields are optional.

Address Format

To read, write and subscribe to data, the OPC UA driver uses the variable declaration string of the OPC UA server it is connecting to. It includes the namespace(ns) of the hierarchy tree followed by the type of identifier string(s), numeric(i), binary(b) or guid(g) and its address. The Data Type is an optional field, if it is not included a default data type is selected based on the datatype of the returned value. For Unsigned data types it needs to be included otherwise.

ns={namespace-index};[s|i|g|b]={Identifier}:{Data Type}

Data Types

The following data types are supported

  • BOOL (boolean)

  • SINT (int 8)

  • USINT (uint 8)

  • BYTE (uint 8)

  • INT (int 16)

  • UINT (uint 16)

  • WORD (uint 16)

  • DINT (int 32)

  • UDINT (uint 32)

  • DWORD (uint 32)

  • LINT (int 64)

  • ULINT (uint 64)

  • LWORD (uint 64)

  • REAL (float)

  • LREAL (double)

  • CHAR (char)

  • WCHAR (2 byte char)

  • STRING (utf-8)

  • WSTRING (utf-16)

Example of a valid OPC UA address:

The following are examples of valid addresses

String address:

ns=2;s=HelloWorld/ScalarTypes/Boolean
ns=2;s=HelloWorld/ScalarTypes/Boolean:BOOL

Numeric address

ns=1;i=1337
ns=1;i=1337:DINT

GUID address:

ns=2;g=09087e75-8e5e-499b-954f-f2a8624db28a
ns=2;g=09087e75-8e5e-499b-954f-f2a8624db28a:REAL

Note the Identifiers s,i,b and g specify the format of the address not the data type of the returned value.

Some useful tips

The namespace (e.g. ns=2) within the address is specific to the server you are connecting to.

More details on OPC UA

OPC UA The OPC Unified Architecture (UA), released in 2008, is a platform independent service-oriented architecture that integrates all the functionality of the individual OPC Classic specifications into one extensible framework.

This multi-layered approach accomplishes the original design specification goals of:

  • Functional equivalence: all COM OPC Classic specifications are mapped to UA

  • Platform independence: from an embedded micro-controller to cloud-based infrastructure

  • Secure: encryption, authentication, and auditing

  • Extensible: ability to add new features without affecting existing applications

  • Comprehensive information modeling: for defining complex information

More details

The client SDK within the Eclipse Milo project is used as the basis for the PLC4X OPC UA driver.