OPC UA Route

OPC UA Overview

The OPCUA route enables communication with OPC UA servers, providing a standardized, cross-platform protocol for industrial automation. It supports multiple authentication modes, security policies, and both NodeId and BrowsePath addressing.

OPC UA is vendor-neutral and widely supported by modern industrial equipment. Use it when you need secure, standardized communication across different manufacturer’s devices.

Basic Syntax

DEFINE ROUTE OPCServer WITH TYPE OPCUA
    ADD OPCUA_CONFIG
        WITH ENDPOINT_URL "opc.tcp://192.168.1.100:4840"
        WITH AUTH_MODE 0
        WITH AUTO_ACCEPT_UNTRUSTED_CERTIFICATES "true"
    ADD MAPPING ProcessData
        WITH EVERY 1 SECOND
        ADD TAG Temperature
            WITH ADDRESS "ns=2;s=Channel1.Device1.Temperature"
            WITH DATA_TYPE "FLOAT"
            WITH SOURCE_TOPIC "opcua/temperature"

Connection Configuration

OPCUA_CONFIG Parameters

string

required

OPC UA server endpoint URL (e.g., opc.tcp://localhost:4840).

integer

Authentication mode:

0 - Anonymous (no authentication)
1 - Username/Password
2 - Certificate

Default: 0.

string

Username for authentication (required if AUTH_MODE is 1).

string

Password for authentication (required if AUTH_MODE is 1).

boolean

Enable security mode. Default: false.

integer

Security policy level:

0 - None
1 - Basic128Rsa15
2 - Basic256
3 - Basic256Sha256
4 - Aes128_Sha256_RsaOaep
5 - Aes256_Sha256_RsaPss

Default: 0.

integer

Message security mode:

0 - None
1 - Sign
2 - SignAndEncrypt

Default: 0.

boolean

Automatically accept untrusted server certificates. Default: false.

boolean

Suppress nonce validation errors. Default: false.

integer

Connection timeout in milliseconds. Default: 90000.

Security Configuration

Anonymous (No Security)
Username/Password
Certificate Authentication

For development or trusted networks:

ADD OPCUA_CONFIG
    WITH ENDPOINT_URL "opc.tcp://192.168.1.100:4840"
    WITH AUTH_MODE 0
    WITH USE_SECURITY "false"
    WITH AUTO_ACCEPT_UNTRUSTED_CERTIFICATES "true"

Basic authentication:

ADD OPCUA_CONFIG
    WITH ENDPOINT_URL "opc.tcp://192.168.1.100:4840"
    WITH AUTH_MODE 1
    WITH USERNAME "opcuser"
    WITH PASSWORD "secure_password"
    WITH USE_SECURITY "true"
    WITH SECURITY_POLICY 3
    WITH MESSAGE_SECURITY 2

For high-security environments:

ADD OPCUA_CONFIG
    WITH ENDPOINT_URL "opc.tcp://192.168.1.100:4840"
    WITH AUTH_MODE 2
    WITH USE_SECURITY "true"
    WITH SECURITY_POLICY 5
    WITH MESSAGE_SECURITY 2

Certificate-based authentication (Mode 2) is currently in development. Use Anonymous (Mode 0) or Username/Password (Mode 1) for production deployments.

NodeId Addressing

OPC UA uses NodeIds to identify variables. The format is: ns=<namespace>;s=<identifier> or ns=<namespace>;i=<numeric_id>

Format	Example	Description
String identifier	`ns=2;s=Channel1.Device1.Tag1`	Most common, human-readable
Numeric identifier	`ns=2;i=1234`	More efficient, used by some servers
GUID identifier	`ns=2;g=12345678-1234-1234-1234-123456789012`	Globally unique identifiers

Finding NodeIds

Use an OPC UA browser tool (like UaExpert, Prosys OPC UA Browser, or similar) to explore the server’s address space and find the correct NodeIds.

BrowsePath Mode

For servers that support it, you can use symbolic paths instead of NodeIds:

boolean

Enable BrowsePath mode - treat all TAG addresses as browse paths instead of NodeIds.

string

Root path for browsing when USE_BROWSE_PATH is enabled. Default: Objects.

BrowsePath Example

ADD OPCUA_CONFIG
    WITH ENDPOINT_URL "opc.tcp://192.168.1.100:4840"
    WITH USE_BROWSE_PATH "true"
    WITH BROWSE_ROOT_PATH "Objects"
ADD MAPPING Tags
    WITH EVERY 1 SECOND
    ADD TAG Temperature
        WITH ADDRESS "Aliases/MyDevice/Temperature"
        WITH DATA_TYPE "FLOAT"
        WITH SOURCE_TOPIC "opcua/temperature"

Data Types

Data Type	OPC UA Type	Description
`BOOLEAN` / `BOOL`	Boolean	True/False value
`SBYTE` / `SINT`	SByte	Signed 8-bit integer
`BYTE` / `USINT`	Byte	Unsigned 8-bit integer
`INT16` / `INT` / `WORD`	Int16	16-bit integer
`UINT16` / `UINT`	UInt16	Unsigned 16-bit integer
`INT32` / `DINT`	Int32	Signed 32-bit integer
`UINT32` / `UDINT` / `DWORD`	UInt32	Unsigned 32-bit integer
`INT64` / `LINT`	Int64	Signed 64-bit integer
`UINT64` / `ULINT` / `LWORD`	UInt64	Unsigned 64-bit integer
`FLOAT` / `FLOAT32` / `REAL`	Float	32-bit floating point
`DOUBLE` / `FLOAT64` / `LREAL`	Double	64-bit floating point
`CHAR`	Char	Single character
`WCHAR`	WChar	Wide character
`TIME`	Time	Time duration
`DATE`	Date	Date value
`TOD`	TimeOfDay	Time of day
`STRING`	String	Unicode string (configurable `STRING_SIZE`)

TAG Configuration

Complete TAG Example

ADD TAG ProcessTemperature
    WITH ADDRESS "ns=2;s=Process.Temperature"
    WITH DATA_TYPE "FLOAT"
    WITH SOURCE_TOPIC "opcua/process/temperature"
    WITH SCALING 1
    WITH OFFSET 0
    WITH UNIT "°C"
    WITH DECIMAL_PLACES 2
    WITH MIN_VALUE -50
    WITH MAX_VALUE 500
    WITH DEADBAND 0.5
    WITH PUBLISH_MODE "JSON"
    WITH WRITABLE "true"
    WITH DESTINATION_TOPIC "opcua/process/temperature/set"
    WITH IS_ARRAY "false"
    WITH DESCRIPTION "Main process temperature sensor"

TAG Parameters

Address Configuration

string

required

OPC UA NodeId (e.g., ns=2;s=MyVariable or ns=2;i=1234) or BrowsePath if USE_BROWSE_PATH is enabled.

string

required

OPC UA data type: BOOLEAN, BYTE, INT16, UINT16, INT32, UINT32, INT64, UINT64, FLOAT, DOUBLE, STRING.

boolean

Indicates if the value is an array. Default: false.

Value Transformation

double

Multiplier for value transformation. Default: 1.0.

double

Offset added after scaling. Default: 0.0.

integer

Decimal places in output. Default: 2.

Filtering

double

Minimum allowed value.

double

Maximum allowed value.

double

Minimum change to trigger publish. Default: 0.0.

Publishing

string

Topic where PLC values are published. Subscribe here to receive sensor data.

string

Output format: VALUE_ONLY or JSON. Default: VALUE_ONLY.

string

Engineering unit for documentation.

string

Human-readable description.

Write Configuration

boolean

Allow writing to this node. Default: false.

string

Topic to send write commands. Publish a value here to write it to the PLC.

Event-Based Operations

For on-demand OPC UA operations (not polling), use the EVENT syntax. Publish a message to SOURCE_TOPIC to trigger the operation; the route executes it and publishes the result to DESTINATION_TOPIC.

Supported Operations

Operation	Description	Query Parameters
`READ`	Read a node value on demand	`node_id`, `data_type`
`WRITE`	Write a value to a node	`node_id`, `data_type`, `value`

Query Parameters

Parameter	Description	Example
`operation`	Operation type: `READ` or `WRITE`	`READ`
`node_id`	OPC UA NodeId (string or numeric)	`ns=2;i=2`, `ns=2;s=Process.Temp`
`data_type`	OPC UA data type	`INT32`, `FLOAT`, `DOUBLE`, `STRING`
`value`	Value to write (WRITE only)	`42`, `23.5`, `"hello"`

Read Example

Read a node value on demand:

ADD EVENT ReadOnDemand
    WITH SOURCE_TOPIC "opcua/commands/read"
    WITH DESTINATION_TOPIC "opcua/responses/read"
    WITH QUERY "{operation: READ, node_id: ns=2;i=2, data_type: INT32}"

Write Example

Write a FLOAT value to a node on demand:

ADD EVENT WriteSetpoint
    WITH SOURCE_TOPIC "opcua/commands/write"
    WITH DESTINATION_TOPIC "opcua/responses/write"
    WITH QUERY "{operation: WRITE, node_id: ns=2;s=Process.Setpoint, data_type: FLOAT, value: 75.0}"

Complete Examples

Simple OPC UA connection with anonymous access:

DEFINE ROUTE OPCServer WITH TYPE OPCUA
    ADD OPCUA_CONFIG
        WITH ENDPOINT_URL "opc.tcp://192.168.1.100:4840"
        WITH AUTH_MODE 0
        WITH AUTO_ACCEPT_UNTRUSTED_CERTIFICATES "true"
    ADD MAPPING ProcessData
        WITH EVERY 1 SECOND
        ADD TAG Temperature
            WITH ADDRESS "ns=2;s=Channel1.Device1.Temperature"
            WITH DATA_TYPE "FLOAT"
            WITH SOURCE_TOPIC "opcua/temperature"
            WITH UNIT "°C"
        ADD TAG Pressure
            WITH ADDRESS "ns=2;s=Channel1.Device1.Pressure"
            WITH DATA_TYPE "FLOAT"
            WITH SOURCE_TOPIC "opcua/pressure"
            WITH UNIT "bar"
        ADD TAG Status
            WITH ADDRESS "ns=2;s=Channel1.Device1.Status"
            WITH DATA_TYPE "INT32"
            WITH SOURCE_TOPIC "opcua/status"

Production setup with encryption:

DEFINE ROUTE SecureOPC WITH TYPE OPCUA
    ADD OPCUA_CONFIG
        WITH ENDPOINT_URL "opc.tcp://192.168.1.100:4840"
        WITH AUTH_MODE 1
        WITH USERNAME "operator"
        WITH PASSWORD "secure_password_here"
        WITH USE_SECURITY "true"
        WITH SECURITY_POLICY 3
        WITH MESSAGE_SECURITY 2
        WITH TIMEOUT 30000
    ADD MAPPING SecureData
        WITH EVERY 500 MILLISECONDS
        ADD TAG CriticalValue
            WITH ADDRESS "ns=2;s=Safety.CriticalValue"
            WITH DATA_TYPE "FLOAT"
            WITH SOURCE_TOPIC "secure/critical"
            WITH PUBLISH_MODE "JSON"

Using symbolic paths:

DEFINE ROUTE BrowsePathOPC WITH TYPE OPCUA
    ADD OPCUA_CONFIG
        WITH ENDPOINT_URL "opc.tcp://192.168.1.100:4840"
        WITH AUTH_MODE 0
        WITH USE_BROWSE_PATH "true"
        WITH BROWSE_ROOT_PATH "Objects"
        WITH AUTO_ACCEPT_UNTRUSTED_CERTIFICATES "true"
    ADD MAPPING ProcessTags
        WITH EVERY 1 SECOND
        ADD TAG Temperature
            WITH ADDRESS "DataAccess/AnalogItems/Temperature"
            WITH DATA_TYPE "DOUBLE"
            WITH SOURCE_TOPIC "opcua/temperature"
        ADD TAG Setpoint
            WITH ADDRESS "DataAccess/AnalogItems/Setpoint"
            WITH DATA_TYPE "DOUBLE"
            WITH SOURCE_TOPIC "opcua/setpoint"
            WITH WRITABLE "true"
            WITH DESTINATION_TOPIC "opcua/setpoint/write"

Reading array data:

DEFINE ROUTE ArrayOPC WITH TYPE OPCUA
    ADD OPCUA_CONFIG
        WITH ENDPOINT_URL "opc.tcp://192.168.1.100:4840"
        WITH AUTH_MODE 0
        WITH AUTO_ACCEPT_UNTRUSTED_CERTIFICATES "true"
    ADD MAPPING ArrayData
        WITH EVERY 1 SECOND
        ADD TAG TemperatureArray
            WITH ADDRESS "ns=2;s=Process.TemperatureArray"
            WITH DATA_TYPE "FLOAT"
            WITH IS_ARRAY "true"
            WITH SOURCE_TOPIC "opcua/temperatures"
            WITH PUBLISH_MODE "JSON"
        ADD TAG StatusBits
            WITH ADDRESS "ns=2;s=Process.StatusBits"
            WITH DATA_TYPE "BOOLEAN"
            WITH IS_ARRAY "true"
            WITH SOURCE_TOPIC "opcua/status/bits"

Connecting to Kepware OPC UA server:

DEFINE ROUTE KepwareServer WITH TYPE OPCUA
    ADD OPCUA_CONFIG
        WITH ENDPOINT_URL "opc.tcp://192.168.1.50:49320"
        WITH AUTH_MODE 0
        WITH AUTO_ACCEPT_UNTRUSTED_CERTIFICATES "true"
    ADD MAPPING KepwareTags
        WITH EVERY 500 MILLISECONDS
        ADD TAG Motor1Speed
            WITH ADDRESS "ns=2;s=Channel1.Device1.Motor1_Speed"
            WITH DATA_TYPE "FLOAT"
            WITH SOURCE_TOPIC "kepware/motor1/speed"
            WITH UNIT "RPM"
        ADD TAG Motor1Current
            WITH ADDRESS "ns=2;s=Channel1.Device1.Motor1_Current"
            WITH DATA_TYPE "FLOAT"
            WITH SOURCE_TOPIC "kepware/motor1/current"
            WITH UNIT "A"
        ADD TAG Motor1Running
            WITH ADDRESS "ns=2;s=Channel1.Device1.Motor1_Running"
            WITH DATA_TYPE "BOOLEAN"
            WITH SOURCE_TOPIC "kepware/motor1/running"

Continuous monitoring with on-demand read and write events in the same route:

DEFINE ROUTE FullOPCSetup WITH TYPE OPCUA
    ADD OPCUA_CONFIG
        WITH ENDPOINT_URL "opc.tcp://192.168.1.100:4840"
        WITH AUTH_MODE 0
        WITH AUTO_ACCEPT_UNTRUSTED_CERTIFICATES "true"
    
    ADD MAPPING ProcessData
        WITH EVERY 1 SECOND
        ADD TAG Temperature
            WITH ADDRESS "ns=2;s=Channel1.Device1.Temperature"
            WITH DATA_TYPE "FLOAT"
            WITH SOURCE_TOPIC "opcua/temperature"
            WITH UNIT "°C"
        ADD TAG Pressure
            WITH ADDRESS "ns=2;s=Channel1.Device1.Pressure"
            WITH DATA_TYPE "FLOAT"
            WITH SOURCE_TOPIC "opcua/pressure"
            WITH UNIT "bar"
    
    ADD EVENT ReadNode
        WITH SOURCE_TOPIC "opcua/commands/read"
        WITH DESTINATION_TOPIC "opcua/responses/read"
        WITH QUERY "{operation: READ, node_id: ns=2;s=Channel1.Device1.Status, data_type: INT32}"
    
    ADD EVENT WriteSetpoint
        WITH SOURCE_TOPIC "opcua/commands/write"
        WITH DESTINATION_TOPIC "opcua/responses/write"
        WITH QUERY "{operation: WRITE, node_id: ns=2;s=Channel1.Device1.Setpoint, data_type: FLOAT, value: 0}"

The MAPPING continuously reads temperature and pressure. To trigger an on-demand status read, publish any message to opcua/commands/read. To write a setpoint, publish to opcua/commands/write.

Security Best Practices

Use Encryption in Production

Always enable security for production deployments:

WITH USE_SECURITY "true"
WITH SECURITY_POLICY 3  // Basic256Sha256
WITH MESSAGE_SECURITY 2  // SignAndEncrypt

Don't Auto-Accept Certificates

In production, properly configure certificate trust:

WITH AUTO_ACCEPT_UNTRUSTED_CERTIFICATES "false"

Instead, exchange certificates between client and server during commissioning.

Use Strong Authentication

Prefer username/password or certificate authentication over anonymous:

WITH AUTH_MODE 1  // or '2' for certificate
WITH USERNAME "operator"
WITH PASSWORD "strong_password_here"

Troubleshooting

Connection Timeout

Verify endpoint URL is correct
Check firewall allows TCP port (usually 4840)
Ensure server is running and accessible
Try increasing TIMEOUT value

Security Rejection

Verify security policy matches server configuration
Check certificate trust (may need to accept in server)
For testing, try WITH AUTO_ACCEPT_UNTRUSTED_CERTIFICATES "true"
Ensure client certificates are properly configured

NodeId Not Found

Use OPC UA browser to verify correct NodeId
Check namespace index (ns=) is correct
Verify node exists in server’s address space
Try BrowsePath mode if NodeId is unclear

Authentication Failed

Verify username and password
Check user has appropriate permissions
Ensure AUTH_MODE matches server requirements

Incorrect Values

Verify DATA_TYPE matches server variable type
Check IS_ARRAY setting for array values
Verify SCALING and OFFSET calculations

Next Steps

Siemens S7

Direct connection to Siemens PLCs.

ADS (Beckhoff)

Connect to TwinCAT systems.

Quick Start

Developing and Managing Coreflux

Coreflux MQTT Broker

LoT Language

Product Updates

OPC UA Overview

Basic Syntax

Connection Configuration

OPCUA_CONFIG Parameters

Security Configuration

NodeId Addressing

Finding NodeIds

BrowsePath Mode

BrowsePath Example

Data Types

TAG Configuration

Complete TAG Example

TAG Parameters

Event-Based Operations

Supported Operations

Query Parameters

Read Example

Write Example

Complete Examples

Security Best Practices

Troubleshooting

Next Steps

Siemens S7

ADS (Beckhoff)

​OPC UA Overview

​Basic Syntax

​Connection Configuration

​OPCUA_CONFIG Parameters

​Security Configuration

​NodeId Addressing

​Finding NodeIds

​BrowsePath Mode

​BrowsePath Example

​Data Types

​TAG Configuration

​Complete TAG Example

​TAG Parameters

​Event-Based Operations

​Supported Operations

​Query Parameters

​Read Example

​Write Example

​Complete Examples

​Security Best Practices

​Troubleshooting

​Next Steps

Siemens S7

ADS (Beckhoff)

OPC UA Overview

Basic Syntax

Connection Configuration

OPCUA_CONFIG Parameters

Security Configuration

NodeId Addressing

Finding NodeIds

BrowsePath Mode

BrowsePath Example

Data Types

TAG Configuration

Complete TAG Example

TAG Parameters

Event-Based Operations

Supported Operations

Query Parameters

Read Example

Write Example

Complete Examples

Security Best Practices

Troubleshooting

Next Steps