Data Types

Node Identifiers (NodeID)

A Node identifier is encoded as a string with the following syntax:

[ns=<namespace_index>;]<type>=<value>

namesace_index

Unsigned 16-bit integer. Should be omitted if the namespace is zero.

type

The Identifier’s type encoded as a string:

i - Integer

s - string

g - GUID

b - opaque byte string

value

Identifier encoded as string depending on type:

i - In decimal form

s - UTF-8 string

g - GUID with small letters of hexademical numbers

b - opaque base64 encoded string.

Examples:

-- integer with namespace index 1.
local numberNode = 'ns=1;i=100'
-- By default, namespace is zero
local numberNode = 'i=100'

-- String
local stringNode = 'ns=1;s=string'
local stringNode = 's=string'

-- Guid
local guidNode = 'ns=100;g=00000001-0002-0003-0405-060708090a0b'
local guidNode = 'g=00000001-0002-0003-0405-060708090a0b'

--ByteString
local byteStringNodeId = 'b=iuZVz8N6YulzlqYeA+P7qAGDCX8Wj1uxon37fqROcqc='
--ByteString with non zero namespace index
local byteStringNodeId = 'ns=1;b=iuZVz8N6YulzlqYeA+P7qAGDCX8Wj1uxon37fqROcqc='

Full source

Additional details can be found in the official OPCUA reference

Encoding and decoding NodeID string notation

toString(id, ns): id - identifier value: can be number, string, GUID, array or bytes

ns - namespace index number or nil

returns string with encoded NodeID
toString( {id=<value>[, ns=<number>]} ): id - identifier value: can be number, string, GUID, array oy bytes.

ns - namespace index number or nil.

returns string with encoded NodeID

Examples:

local nodeId = require("opcua.node_id")

-- Numeric

-- 'i=100'
local nodeIdString = nodeId.toString(100)
local nodeIdString = nodeId.toString({id=100})

-- 'ns=1;i=100'
local nodeIdString = nodeId.toString(100, 1)
local nodeIdString = nodeId.toString({id=100, 1})

-- String

-- 's=hello'
local nodeIdString = nodeId.toString('hello')
local nodeIdString = nodeId.toString({id='hello'})

-- 'ns=1;s=hello'
local nodeIdString = nodeId.toString('hello', 1)
local nodeIdString = nodeId.toString({id='hello', ns=1})

-- GUID
local guid = {
    data1 = 1, data2 = 2, data3 = 3,
    data4 = 4, data5 = 5, data6 = 6,
    data7 = 7, data8 = 8, data9 = 9,
    data10 = 10, data11 = 11
  }

-- 'g=00000001-0002-0003-0405-060708090a0b'
local nodeIdString = nodeId.toString(guid)
local nodeIdString = nodeId.toString({id=guid})

-- 'ns=1;g=00000001-0002-0003-0405-060708090a0b'
local nodeIdString = nodeId.toString(guid, 1)
local nodeIdString = nodeId.toString({id=guid, ns=1})

-- ByteString

-- 'b=AQIDBAUGBw=='
local nodeIdString = nodeId.toString({1,2,3,4,5,6,7})
local nodeIdString = nodeId.toString({id={1,2,3,4,5,6,7}})

-- 'ns=1;b=AQIDBAUGBw=='
local nodeIdString = nodeId.toString({1,2,3,4,5,6,7}, 1)
local nodeIdString = nodeId.toString({id={1,2,3,4,5,6,7}, ns=1})

Full source

fromString(string): string - encoded NodeID

return - table with fields: ns - namepsace index, id - value

Examples:

local nodeId = require("opcua.node_id")

-- Numeric

-- {id=100}
local nodeIdtbl = nodeId.fromString('i=100')

-- {id=100,ns=1}
local nodeIdtbl = nodeId.fromString('ns=1;i=100')

-- String

-- {id='hello'}
local nodeIdtbl = nodeId.toString('s=hello')

-- {id='hello', ns=1}
local nodeIdtbl = nodeId.toString('ns=1;s=hello')

-- GUID

--   guid = {
--     data1 = 1, data2 = 2, data3 = 3,
--     data4 = 4, data5 = 5, data6 = 6,
--     data7 = 7, data8 = 8, data9 = 9,
--     data10 = 10, data11 = 11
--   }
--
--  nodeIdtbl = {id = guid}
local nodeIdtbl = nodeId.fromString('g=00000001-0002-0003-0405-060708090a0b')

-- 'ns=1;g=00000001-0002-0003-0405-060708090a0b'
local nodeIdtbl = nodeId.fromString('ns=1;g=00000001-0002-0003-0405-060708090a0b')

-- ByteString
-- byteString = {1,2,3,4,5,6,7}

-- {id=byteString}
local nodeIdtbl = nodeId.toString('b=AQIDBAUGBw==')

-- {id={1,2,3,4,5,6,7}, ns=1}
local nodeIdtbl = nodeId.fromString('ns=1;b=AQIDBAUGBw==')

Full source

Variant

All values in OPC-UA can be represented with the universal data structure Variant. Variants can represent either a scalar value or a multidimensional array. Multidimensional arrays can only be of one type in Lua. A Variant is represented as a table with one field, where the key defines type of the value stored in the table.

Variant example

local uint32 = {
  UInt32 = 0
}

local uint32_array = {
  UInt32 = {1,2,3,4,5,6,7}
}


local localized_text = {
  LocalizedText = {
    Locale = "en-US",
    Text = "This is a text string"
  }
}
local localized_text_array = {
  LocalizedText = {
    { #1
      Locale = "en-US",
      Text = "This is a text string"
    },
    { #2
      Text = "This is a text string without locale"
    }
  }
}

The fields you may set in a Variant table

Byte

Sbyte

Int16

UInt16

Int32

UInt32

Int64

UInt64

Float

Double

DateTime

Guid

LocalizedText

QualifiedName

NodeId

StatusCode

String

QualifiedName

DataValue

Variant

ExtensionObject

OPC-UA Types

Sbyte
Signed 8-bit integer

Byte
Unsigned 8-bit integer

Int16
Signed 16-bit integer

UInt16
Unsigned 16-bit integer

Int32
Signed 32-bit integer

UInt32
Unsigned 32-bit integer

Int64
Signed 64-bit integer

UInt64
Unsigned 64-bit integer

Float
Real 32-bit number

Double
Real 64-bit number

DateTime
Real 64-bit number. Represents milliseconds since Jan. 1, 1970.

String
String.

Guid
Guid in form of table:
local guid = {
  Data1 = 0x123456, -- uint32
  Data2 = 0x1234,   -- uint16
  Data3 = 0x1234,   -- uint16
  Data4 = 0x23,     -- byte
  Data5 = 0x23,     -- byte
  Data6 = 0x21,     -- byte
  Data7 = 0x21,     -- byte
  Data8 = 0x21,     -- byte
  Data9 = 0x21,     -- byte
  Data10 = 0x21,    -- byte
  Data11 = 0x21     -- byte
}
TBD - String representaion

LocalizedText
Localized text. A table with two fields:

locale - optional locale name. The default locale is used if nil

text - string with content

Example:
local localizedText = {
  locale = "en-US",
  text = "This is localized text"
}

local localizedText = {
  text = "This is localized text"
}

QualifiedName
Qualified Name is the service identifier of a node, which consist of a namespace index and text label.
local qualifiedName = {
  nsi = 1,
  name = "Node Name"
}
NodeID
Identifier of a node. Explaned in Node Identifiers (NodeID)

StatusCode
Error code.

DataValue

Complete variable value.

local dataValue = {
  Value = {UInt32 = 100}, -- Variant(v.Value)
  StatusCode = ua.StatusCode.Good, -- StatusCode (Optional)
  SourceTimestamp = os.time(), -- DateTime (Optional)
  ServerTimestamp = os.time(), -- DateTime (Optional)
  SourcePicoseconds = 0, -- UInt16 (Optional)
  ServerPicoseconds = 0, -- UInt16 (Optional)
}

Variant

Explained in section Variant

ExtensionObject

Any data type that can be encoded with OPC-UA encoding schemas (binary, XML, Json).

local extensionObject = {
  typeId = "i=7617", -- (NodeId) DataType node that represent encoding.
  body = {0,1,2,3,4,5} -- (ByteString) Encoded value (binary, XML, JSON)
}

activateSessionResponse

ServerNonce
A random number that should not be reused.

Results[]
list of SatusCodes

addNodesResponse

Rresults[] (array)

StatusCode
StatusCode for the added Node

AddedNodeId
Server assigned NodeId for the added Node. The NodeId is nil if the operation failed.

browseParameters

RequestedMaxReferencesPerNode
Maximum number of reference types that will be processed. Zero - unlimited

NodesToBrowse[] Array of nodes to browse:

NodeId (NodeId)
The identifier of a node to browse

ReferenceTypeId NodeId
Reference type identifier

BrowseDirection ua.Types.BrowseDirection
Browsing direction

nodeClassMask ua.Types.NodeClass
The class of nodes to include in the response

ResultMask ua.Types.BrowseResultMask
A mask that specifies the set of data to include in the response

IncludeSubtypes Boolean
If 1 then all subtypes of the specified ReferenceTypeId will be followed

browseResult

Results[] (array)

The result is provided as a Lua table. Every element index corresponds to an element in the request.

StatusCode

The ‘status’ of browsing the requested node.

References

Array of references.

NodeId (NodeId): Node identifier
ReferenceTypeId (NodeId): Reference type identifier
IsForward (Boolean): Browsing direction
BrowseName (QualifiedName): Service name of a node
DisplayName (LocalizedText): User labe of a node
NodeClass (Int32): Node class
TypeDefinition (NodeId): The node’s type definition

closeSecureChannelResponse

Empty table

closeSessionResponse

Empty table

createSessionResponse

ResponseHeader

SessionId (Node Identifiers (NodeID))
A unique NodeId assigned by the Server to the Session.

AuthenticationToken (Node Identifiers (NodeID))
A unique identifier assigned by the Server to the Session

RevisedSessionTimeout (double)
Actual maximum number of milliseconds that a Session shall remain open without activity.

ServerNonce (bytestring)
A random number that should never be used in any other request.

ServerCertificate
The Application Instance Certificate issued to the Server

ServerEndpoints
List of Endpoints that the Server supports.

ServerSignature
This is a signature generated with the private key associated with the serverCertificate.

MaxRequestMessageSize (uint32)
The maximum size, in bytes, for the body of any request message.

findServersResponse

Servers[]
List of Servers that meet criteria specified in the request.

ApplicationUri

ProductUri

ApplicationName

ApplicationType

GatewayServerUri

DiscoveryProfileUri

DiscoveryUrls

getEndpointsResponse

Endpoints[]

EndpointUrl

Server

ServerCertificate

SecurityMode

SecurityPolicyUri

UserIdentityTokens

TransportProfileUri

SecurityLevel

openSecureChannelResponse

ResponseHeader

SecurityToken

ChannelId (uint32)
A unique identifier for the SecureChannel.

TokenId (uint32)
A unique identifier for a single SecurityToken within the channel.

CreatedAt (dateTime)
The time when the SecurityToken was created.

RevisedLifetime (uint32)
The lifetime of the SecurityToken in milliseconds.

readResponse

Results[] (dataValue)
List of Attribute values

writeResponse

Results[] (statusCode)
List of results for the Nodes to write