QuickOPC User's Guide and Reference
DiscoverLocalServers(IEasyUAClient,String,Boolean) Method



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OpcLabs.EasyOpcUA Assembly > OpcLabs.EasyOpc.UA Namespace > IEasyUAClientExtension Class > DiscoverLocalServers Method : DiscoverLocalServers(IEasyUAClient,String,Boolean) Method
The client object that will perform the operation.
The name of the machine that runs the discovery server that will be used for discovery task.
Determines whether one element will be returned for each discovery URI.
Discovers available OPC-UA servers and returns information about them, using the specified discovery host.
Syntax
'Declaration
 
<ExtensionAttribute()>
<ElementsNotNullAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function DiscoverLocalServers( _
   ByVal client As IEasyUAClient, _
   ByVal discoveryHost As String, _
   ByVal flat As Boolean _
) As UADiscoveryElementCollection
 
'Usage
 
Dim client As IEasyUAClient
Dim discoveryHost As String
Dim flat As Boolean
Dim value As UADiscoveryElementCollection
 
value = IEasyUAClientExtension.DiscoverLocalServers(client, discoveryHost, flat)

Parameters

client
The client object that will perform the operation.
discoveryHost
The name of the machine that runs the discovery server that will be used for discovery task.
flat
Determines whether one element will be returned for each discovery URI.

Return Value

Returns a collection of application elements (servers, OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement).
Exceptions
ExceptionDescription

A null reference (Nothing in Visual Basic) is passed to a method that does not accept it as a valid argument.

This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.

The OPC UA operation has failed. This operation exception in uniformly used to allow common handling of various kinds of errors. The System.Exception.InnerException always contains information about the actual error cause.

This is an operation error that depends on factors external to your program, and thus cannot be always avoided. Your code must handle it appropriately.

Remarks

This method uses the so-called Local Discovery Server (LDS). You can influence how the discovery works using the properties in static SharedParameters.

Invokes the FindServers service.

See also in Knowledge Base: Technical note-OPC UA Discovery in QuickOPC.

When the flat parameter is false, the discovery query returns one OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement for each application found, and its OpcLabs.EasyOpc.UA.Discovery.IUAReadOnlyApplicationElement.DiscoveryUriStrings property contains one or more application discovery URLs.

When the flat parameter is true, the discovery query returns one OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement for each discovery URL of each application found. In this case, the OpcLabs.EasyOpc.UA.Discovery.IUAReadOnlyApplicationElement.DiscoveryUriStrings property of each returned application element contains precisely one string, and you can therefore use the OpcLabs.EasyOpc.UA.Discovery.IUAReadOnlyApplicationElement.DiscoveryUriString property instead to obtain the discovery URL.

Requirements

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2016, Windows Server 2022; .NET: Linux, macOS, Microsoft Windows

See Also