SignalR API

The SignalR API utilizes the Microsoft SignalR library. SignalR is a library for developers that simplifies the process of adding real-time web functionality to applications. Real-time web functionality is the ability to have server code push content to connected clients instantly as it becomes available, rather than having the server wait for a client to request new data.

In the OPC UA API the SignalR API is primarily used for subscribing to data and event values. This means that the API calls back to the client (e.g browser), when values have changed.

The SignalR API exposes a set of RPC-methods. The client must then implement corresponding callback methods to receive results fromt the API.

Hub

The address of the SignalR hub is /OpcUaHub.

The methods below can be reached through this hub.

Methods

Method	Callback
ReadValues(string requestId, ReadValuesRequest[] request)	OnReadValues(string requestId, ReadValuesResponse[] response)
WriteValues(string requestId, WriteValuesRequest[] request)	OnWriteValues(string requestId, WriteValuesResponse[] response)
ReadDataTypes(string requestId, ReadDataTypesRequest request)	OnReadDataTypes(string requestId, ReadDataTypesResponse response)
ReadAttributes(string requestId, ReadAttributesRequest[] request)	OnReadAttributes(string requestId, ReadAttributesResponse[] response
WriteAttributes(string requestId, WriteAttributesRequest[] request)	OnWriteAttributes(string requestId, WriteAttributesResponse[] response)
HistoryReadRaw(string requestId, ReadHistoryRawValuesRequest request)	OnHistoryReadRaw(string requestId, ReadHistoryRawValuesResponse response)
HistoryReadProcessed(string requestId, ReadHistoryProcessedValuesRequest request)	OnHistoryReadProcessed(string requestId, ReadHistoryProcessedValuesResponse response)
GetHistoricalAggregates(string requestId, HistoryAggregateRequest request)	OnGetHistoricalAggregates(string requestId, HistoryAggregateResponse response)
HistoryWriteValues(string requestId, HistoryWriteRequest request)	OnHistoryWriteValues(string requestId, HistoryWriteResponse response)
ReadEventsHistory(string requestId, ReadEventHistoryRequest request)	OnReadEventsHistory(string requestId, ReadEventHistoryResponse response)
ReadEventsHistoryExtended(string requestId, ReadEventHistoryExtendedRequest request)	OnReadEventsHistoryExtended(string requestId, ReadEventHistoryExtendedResponse response)
WriteEventsHistory(string requestId, WriteEventHistoryRequest request)	OnWriteEventsHistory(string requestId, WriteEventHistoryResponse response)
WriteEventsHistoryExtended(string requestId, WriteEventHistoryExtendedRequest request)	OnWriteEventsHistoryExtended(string requestId, WriteEventHistoryExtendedResponse response)
GetEventFields(string requestId)	OnEventFieldsFetched(string requestId, EventFieldDefinition[] fields)
GetEventTypes(string requestId, GetEventTypesRequest request)	OnGetEventTypes(string requestId, GetEventTypesResponse fields)
AddEventComments(string requestId, AddCommentRequest[] request )	OnEventsCommented(string requestId, AddCommentResponse[] response)
ConfirmEvents(string requestId, ConfirmRequest[] request)	On#stringEventsConfirmed(string requestId, ConfirmResponse[] response)
AcknowledgeEvents(string requestId, AcknowledgeRequest[] request)	OnEventsAcknowledged(string requestId, AcknowledgeResponse[] response)
CreateEventSubscription(string requestId, CreateEventSubscriptionRequest request)	OnEventSubscriptionCreated(string requestId, CreateEventSubscriptionResponse response)
	OnEvents(EventsChangedResponse response)
CloseEventSubscription(string requestId, CloseEventSubscriptionRequest request)	OnEventSubscriptionClosed(string requestId, CloseEventSubscriptionResponse response)
CreateDataValueSubscription(string requestId, CreateDataValueSubscriptionRequest request, bool startSubscription)	OnDataValueSubscriptionCreated(string requestId, CreateDataValueSubscriptionResponse response)
	OnDataValuesUpdate(DataValuesChangedResponse response)
CloseDataValueSubscription(string requestId, CloseDataValueSubscriptionRequest request)	OnDataValueSubscriptionClosed(string requestId, CloseDataValueSubscriptionResponse response)
StartDataValueSubscription(string requestId, string subscriptionid)	[OnDataValueSubscriptionStarted](string requestId, #ondatavaluesubscriptionstarted)(StartDataValueSubscriptionResponse response)
GetNamespaces(string requestId, NamespacesRequest request)	OnNamespacesFetched(string requestId, NamespaceResponse response)
Browse(string requestId, BrowseRequest request)	OnBrowse(string requestId, BrowseResponse resonse)
BrowseMulti(string requestId, BrowseMultiRequest request)	OnBrowseMulti(string requestId, MultiBrowseResponse resonse)
BrowseChildren(string requestId, ChildrenRequest request)	OnBrowseChildren(string requestId, BrowseResponse resonse)
BrowseProperties(string requestId, BrowsePropertiesRequest request)	OnBrowseProperties(string requestId, BrowseResponse resonse)
BrowsePropertiesMulti(string requestId, BrowsePropertiesMultiRequest request)	OnBrowsePropertiesMulti(string requestId, MultiBrowseResponse resonse)
TranslateBrowsePathsToNodeIds(string requestId, TranslateBrowsePathsRequest request)	OnTranslateBrowsePathsToNodeIds(string requestId, TranslateBrowsePathsResponse resonse)

ReadValues

This method is called to read values (i.e. the value of attribute with id = 13) of one or more nodes.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	array of ReadValuesRequest	Contains the nodes to read and the connection info

OnReadValues

This is the callback method for ReadValues.

Parameter	Type	Description
requestId	String	The string which is passed in ReadValues
response	array of ReadValuesResponse	Contains the values of the nodes if successful.

The second parameter is an array of ReadValuesResponse, and contains the values (i.e. the value of attribute with id = 13) of the nodes or an error code if unsuccessful. The order of the arrays are the same as the order of the arrays in ReadValues.

WriteValues

This method is called to write values (i.e. the value of attribute with id = 13) to one or more nodes.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	array of WriteValuesRequest	Contains the nodes and values to write and the connection info

OnWriteValues

This is the callback method for WriteValues.

Parameter	Type	Description
requestId	String	The string which is passed in WriteValues
response	array of WriteValuesResponse	Contains the status of the write operation.

ReadDataTypes

This method is called to read datatypes (i.e. the value of attribute with id = 14) of one or more nodes.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	ReadDataTypesRequest	Contains the nodes to read and the connection info

OnReadDataTypes

This is the callback method for ReadDataTypes.

Parameter	Type	Description
requestId	String	The string which is passed in ReadDataTypes
response	array of ReadDataTypesResponse	Contains the datatypes of the nodes if successful.

ReadAttributes

This method is called to read attributes of one or more nodes.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	array of ReadAttributesRequest	Contains the nodes and attribute ids to read and the connection info

OnReadAttributes

This is the callback method for ReadAttributes.

Parameter	Type	Description
requestId	String	The string which is passed in ReadAttributes
response	array of ReadAttributesResponse	Contains the values of the attributes of the nodes if successful.

The second parameter is an array of ReadAttributesResponse, and contains the values of the attributes or an error code if unsuccessful. The order of the arrays are the same as the order of the arrays in ReadAttributes.

WriteAttributes

This method is called to write attributes to one or more nodes.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	array of WriteAttributesRequest	Contains the nodes, attribute ids and values to write and the connection info

OnWriteAttributes

This is the callback method for WriteAttributes.

Parameter	Type	Description
requestId	String	The string which is passed in WriteAttributes
response	array of WriteAttributesResponse	Contains the status of the write operation.

HistoryReadRaw

This method reads raw history data from an OPC UA Server.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	ReadHistoryRawValuesRequest	Contains the nodes, attribute ids to read and the connection info

OnOnHistoryReadRaw

This is the callback method for HistoryReadRaw.

Parameter	Type	Description
requestId	String	The string which is passed in HistoryReadRaw
response	ReadHistoryRawValuesResponse	Contains the result of the read operation.

HistoryReadProcessed

This method reads processed data from an OPC UA Server.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	ReadHistoryProcessedValuesRequest	Contains the nodes, attribute ids and other arguments needed for reading processed data.

OnHistoryReadProcessed

This is the callback method for HistoryReadProcessed.

Parameter	Type	Description
requestId	String	The string which is passed in HistoryReadProcessed
response	ReadHistoryProcessedValuesResponse	Contains the result of the read operation.

GetHistoricalAggregates

This method gets the available historical aggregates from an OPC UA Server.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	HistoricalAggregateRequest

OnGetHistoricalAggregates

This is the callback method for GetHistoricalAggregates.

Parameter	Type	Description
requestId	String	The string which is passed in GetHistoricalAggregates
response	HistoryAggregateResponse	Contains the historical aggregates for the OPC UA Server.

HistoryWriteValues

This method writes historical data to an OPC UA Server.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	HistoryWriteRequest	Contains the values to write.

OnHistoryWriteValues

This is the callback method for HistoryWriteValues.

Parameter	Type	Description
requestId	String	The string which is passed in HistoryWriteValues
response	HistoryWriteResponse	Contains the result of the write operation.

ReadEventsHistory

This method reads the event history from an OPC UA Server.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	ReadEventHistoryRequest	Contains the information needed for reading event history

OnReadEventsHistory

This is the callback method for ReadEventsHistory.

Parameter	Type	Description
requestId	String	The string which is passed in ReadEventsHistory
response	ReadEventHistoryResponse	Contains the historical events.

ReadEventsHistoryExtended

This method reads the event history from an OPC UA Server. The difference between this method and ReadEventsHistory is that the fields to be queried for are not predefined.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	ReadEventHistoryExtendedRequest	Contains the information needed for reading event history

OnReadEventsHistoryExtended

This is the callback method for ReadEventsHistoryExtended.

Parameter	Type	Description
requestId	String	The string which is passed in ReadEventsHistoryExtended
response	ReadEventHistoryExtendedResponse	Contains the historical events.

WriteEventsHistory

This method writes event history to an OPC UA Server.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	WriteEventHistoryRequest	Contains the information needed for writing event history

OnWriteEventsHistory

This is the callback method for WriteEventsHistory.

Parameter	Type	Description
requestId	String	The string which is passed in WriteEventsHistory
response	WriteEventHistoryResponse	Contains the result of the write operation.

WriteEventsHistoryExtended

This method writes event history to an OPC UA Server.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	WriteEventHistoryExtendedRequest	Contains the information needed for writing event history

OnWriteEventsHistoryExtended

This is the callback method for WriteEventsHistoryExtended.

Parameter	Type	Description
requestId	String	The string which is passed in WriteEventsHistoryExtended
response	WriteEventHistoryExtendedResponse	Contains the result of the write operation.

GetEventFields

This method gets the predefined event fields. These event fields are usually the most queried, and are available for querying in an easy way. This can be seen in ReadEventHistoryRequest.

Parameter	Type	Description
requestId	String	A string which is returned in the callback

OnEventFieldsFetched

This is the callback method for GetEventFields.

Parameter	Type	Description
requestId	String	The string which is passed in GetEventFields
response	array of EventFieldDefinition	Contains the predefined events which can be queried in ReadEventHistoryRequest.

GetEventTypes

This method gets Event types.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	GetEventTypesRequest	Contains the information needed getting event-types

OnGetEventTypes

This is the callback method for GetEventTypes.

Parameter	Type	Description
requestId	String	The string which is passed in GetEventTypes
response	GetEventTypesResponse	Contains the event types.

AddEventComments

This method adds comment to an event.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	array of AddCommentRequest	Contains the event id and comment

OnEventsCommented

This is the callback method for AddEventComments.

Parameter	Type	Description
requestId	String	The string which is passed in AddEventComments
response	array of AddCommentResponse	The response tells whether the AddComment was successful.

ConfirmEvents

This method confirms events.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	array of ConfirmRequest	Contains the event id and comment

OnEventsConfirmed

This is the callback method for ConfirmEvents.

Parameter	Type	Description
requestId	String	The string which is passed in ConfirmEvents
response	array of ConfirmResponse	The response tells whether the Confirm was successful.

AcknowledgeEvents

This method acknowledges events.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	array of AcknowledgeRequest	Contains the event id and comment

OnEventsAcknowledged

This is the callback method for AcknowledgeEvents.

Parameter	Type	Description
requestId	String	The string which is passed in AcknowledgeEvents
response	array of AcknowledgeResponse	The response tells whether the Acknowledge was successful.

CreateEventSubscription

This method creates an event subscription. When subscribing to events two callback methods are involved. First the OnEventSubscriptionCreated is invoked telling whether the subscription was created correctly. Then as events happen the OnEvents method will be invoked, containing all the events which have occured since the last OnEvents call. The first OnEvents call after a successful event subscription has occured, will contain the current state of all the applicable event sources.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	CreateEventSubscriptionRequest	Contains the information needed to create event subscription

OnEventSubscriptionCreated

This is the callback method invoked after the CreateEventSubscription has been called.

Parameter	Type	Description
requestId	String	The string which is passed in CreateEventSubscription.
response	CreateEventSubscriptionResponse	The response tells whether the subscription has been created successfully.

OnEvents

This is the callback method invoked when the events have occured for the subscription.

Parameter	Type	Description
response	EventsChangedResponse	Contains the events which have occured since the previous OnEvents invocation.

CloseEventSubscription

This method closes (stops) an event subscription. If this method is not called, it will be automatically called when the client disconnects.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	CloseEventSubscriptionRequest	Contains the id of the subscription to be closed.

OnEventSubscriptionClosed

This is the callback method for CloseEventSubscription.

Parameter	Type	Description
requestId	String	The string which is passed in CloseEventSubscription.
response	CloseEventSubscriptionResponse	The response tells whether the subscription has been closed successfully.

CreateDataValueSubscription

This method creates a data value subscription. When subscribing to data values two callback methods are involved. First the OnDataValueSubscriptionCreated is invoked telling whether the subscription was created correctly. Then as data values change the OnDataValuesUpdate method will be invoked, containing all the data values which have changed since the last OnDataValuesUpdate call.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	CreateDataValueSubscriptionRequest	Contains the information needed to create data value subscription
startSubscription	Boolean	If true the subscription starts right away. If false the StartDataValueSubscription has to be called.

OnDataValueSubscriptionCreated

This is the callback method invoked after the CreateDataValueSubscription has been called.

Parameter	Type	Description
requestId	String	The string which is passed in CreateDataValueSubscription.
response	CreateDataValueSubscriptionResponse	The response tells whether the subscription has been created successfully.

OnDataValuesUpdate

This is the callback method invoked when the data values have changed for the subscription.

Parameter	Type	Description
response	DataValuesChangedResponse	Contains the data values which have changed since the previous OnDataValuesUpdate invocation.

CloseDataValueSubscription

This method closes (stops) a data value subscription. If this method is not called, it will be automatically called when the client disconnects.

Parameter	Type	Description
requestId	String	A string which is returned in the callback
request	CloseDataValueSubscriptionRequest	Contains the id of the subscription to be closed.

OnDataValueSubscriptionClosed

This is the callback method for CloseDataValueSubscription.

Parameter	Type	Description
requestId	String	The string which is passed in CloseDataValueSubscription.
response	CloseDataValueSubscriptionResponse	The response tells whether the subscription has been closed successfully.

StartDataValueSubscription

This method starts a subscription created by CreateDataValueSubscription.

Parameter	Type	Description
requestId	String	A string which is returned in the callback.
subscriptionid	String	The id of the subscription to be started.

OnDataValueSubscriptionStarted

This is the callback method for StartDataValueSubscription.

Parameter	Type	Description
requestId	String	The string which is passed in StartDataValueSubscription.
response	StartDataValueSubscriptionResponse	The response tells whether the subscription has been started successfully.

GetNamespaces

This method gets the namespaces of a OPC UA Server.

Parameter	Type	Description
requestId	String	A string which is returned in the callback.
request	NamespacesRequest

OnNamespacesFetched

This is the callback method for GetNamespaces.

Parameter	Type	Description
requestId	String	The string which is passed in GetNamespaces.
response	NamespaceResponse	Contains the namespaces

Browse

This method is used to browse the UA Address Space for nodes.

Parameter	Type	Description
requestId	String	A string which is returned in the callback.
request	BrowseRequest	The information needed to start a browse operation.

OnBrowse

This is the callback method for Browse.

Parameter	Type	Description
requestId	String	The string which is passed in Browse.
response	BrowseResponse	Contains the references to nodes.

BrowseMulti

This method is used to browse with multiple source nodes the UA Address Space for nodes.

Parameter	Type	Description
requestId	String	A string which is returned in the callback.
request	BrowseMultiRequest	Browse request

OnBrowseMulti

This is the callback method for BrowseMulti.

Parameter	Type	Description
requestId	String	The string which is passed in BrowseMulti.
response	MultiBrowseResponse	Contains the references to nodes.

BrowseChildren

This method is used to browse the UA Address Space for children nodes. The children nodes are defined as nodes of node class: Variable, Object, DataType, VariableType or ObjectType.

Parameter	Type	Description
requestId	String	A string which is returned in the callback.
request	ChildrenRequest	The information needed to start a browse children operation.

OnBrowseChildren

This is the callback method for BrowseChildren.

Parameter	Type	Description
requestId	String	The string which is passed in BrowseChildren.
response	BrowseResponse	Contains the references to nodes.

BrowseProperties

This method is used to browse the UA Address Space for properties. The property nodes are defined as nodes of node class: Variable which has a HasProperty reference.

Parameter	Type	Description
requestId	String	A string which is returned in the callback.
request	BrowsePropertiesRequest	The information needed to start a browse for properties operation.

OnBrowseProperties

This is the callback method for BrowseProperties.

Parameter	Type	Description
requestId	String	The string which is passed in BrowseProperties.
response	BrowseResponse	Contains the references to nodes.

BrowsePropertiesMulti

This method is used to browse the UA Address Space for properties. The property nodes are defined as nodes of node class: Variable which has a HasProperty reference.

Parameter	Type	Description
requestId	String	A string which is returned in the callback.
request	BrowsePropertiesMultiRequest	The information needed to start a browse for properties operation.

OnBrowsePropertiesMulti

This is the callback method for BrowsePropertiesMulti.

Parameter	Type	Description
requestId	String	The string which is passed in BrowsePropertiesMulti.
response	MultiBrowseResponse	Contains the references to nodes.

TranslateBrowsePathsToNodeIds

Translates browse paths to node ids.

Parameter	Type	Description
requestId	String	A string which is returned in the callback.
request	TranslateBrowsePathsRequest	Contains starting nodes and relative paths.

OnTranslateBrowsePathsToNodeIds

This is the callback method for TranslateBrowsePathsToNodeIds.

Parameter	Type	Description
requestId	String	The string which is passed in TranslateBrowsePathsToNodeIds.
response	TranslateBrowsePathsResponse	Contains the node ids for the relative paths.

OPC UA Values REST API