Discovers available OPC-UA servers and returns information about them, using the specified discovery host.
Syntax
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.
Return Value
Returns a collection of application elements (servers,
OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement).
Exceptions
Exception | Description |
System.ArgumentNullException |
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. |
OpcLabs.EasyOpc.UA.OperationModel.UAException |
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. |
Example
.NET
// This example shows how to obtain application URLs of all OPC Unified Architecture servers on a given machine.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
using System;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.Discovery;
using OpcLabs.EasyOpc.UA.OperationModel;
namespace UADocExamples._EasyUAClient
{
class DiscoverLocalServers
{
public static void Overload1()
{
// Instantiate the client object.
var client = new EasyUAClient();
// Obtain collection of server elements.
UADiscoveryElementCollection discoveryElementCollection;
try
{
discoveryElementCollection = client.DiscoverLocalServers("opcua.demo-this.com");
}
catch (UAException uaException)
{
Console.WriteLine($"*** Failure: {uaException.GetBaseException().Message}");
return;
}
// Display results.
foreach (UADiscoveryElement discoveryElement in discoveryElementCollection)
Console.WriteLine($"discoveryElementCollection[\"{discoveryElement.DiscoveryUriString}\"].ApplicationUriString: {discoveryElement.ApplicationUriString}");
// Example output:
//
//discoveryElementCollection["opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"].ApplicationUriString: urn: DEMO - 5:UA Sample Server
//discoveryElementCollection["http://opcua.demo-this.com:51211/UA/SampleServer"].ApplicationUriString: urn: DEMO - 5:UA Sample Server
//discoveryElementCollection["https://opcua.demo-this.com:51212/UA/SampleServer/"].ApplicationUriString: urn: DEMO - 5:UA Sample Server
//discoveryElementCollection["http://opcua.demo-this.com:62543/Quickstarts/AlarmConditionServer"].ApplicationUriString: urn: opcua.demo - this.com:Quickstart Alarm Condition Server
//discoveryElementCollection["opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer"].ApplicationUriString: urn: opcua.demo - this.com:Quickstart Alarm Condition Server
}
}
}
# This example shows how to obtain application URLs of all OPC Unified Architecture servers on a given machine.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
#requires -Version 5.1
using namespace OpcLabs.EasyOpc.UA
using namespace OpcLabs.EasyOpc.UA.Discovery
using namespace OpcLabs.EasyOpc.UA.OperationModel
# The path below assumes that the current directory is [ProductDir]/Examples-NET/PowerShell/Windows .
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUA.dll"
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUAComponents.dll"
# Instantiate the client object.
$client = New-Object EasyUAClient
# Obtain collection of server elements.
try {
$discoveryElementCollection = [IEasyUAClientExtension]::DiscoverLocalServers($client, "opcua.demo-this.com")
}
catch [UAException] {
Write-Host "*** Failure: $($PSItem.Exception.GetBaseException().Message)"
return
}
# Display results.
foreach ($discoveryElement in $discoveryElementCollection) {
Write-Host "discoveryElementCollection[`"$($discoveryElement.DiscoveryUriString)`"].ApplicationUriString: $($discoveryElement.ApplicationUriString)"
}
# Example output:
#
#discoveryElementCollection["opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"].ApplicationUriString: urn:DEMO-5:UA Sample Server
#discoveryElementCollection["http://opcua.demo-this.com:51211/UA/SampleServer"].ApplicationUriString: urn:DEMO-5:UA Sample Server
#discoveryElementCollection["https://opcua.demo-this.com:51212/UA/SampleServer/"].ApplicationUriString: urn:DEMO-5:UA Sample Server
#discoveryElementCollection["http://opcua.demo-this.com:62543/Quickstarts/AlarmConditionServer"].ApplicationUriString: urn:opcua.demo-this.com:Quickstart Alarm Condition Server
#discoveryElementCollection["opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer"].ApplicationUriString: urn:opcua.demo-this.com:Quickstart Alarm Condition Server
# This example shows how to obtain application URLs of all OPC Unified Architecture servers on the specified host.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python .
# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc
# Import .NET namespaces.
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.OperationModel import *
# Instantiate the client object.
client = EasyUAClient()
# Obtain collection of server elements.
try:
discoveryElementCollection = IEasyUAClientExtension.DiscoverLocalServers(client, 'opcua.demo-this.com')
except UAException as uaException:
print('*** Failure: ' + uaException.GetBaseException().Message)
exit()
# Display results.
for discoveryElement in discoveryElementCollection:
print('DiscoveryElementCollection["', discoveryElement.DiscoveryUriString, '"].ApplicationUriString: ',
discoveryElement.ApplicationUriString, sep='')
' This example shows how to obtain application URLs of all OPC Unified Architecture servers on a given machine.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.Discovery
Imports OpcLabs.EasyOpc.UA.OperationModel
Namespace _EasyUAClient
Friend Class DiscoverLocalServers
Public Shared Sub Overload1()
' Instantiate the client object
Dim client = New EasyUAClient()
' Obtain collection of server elements
Dim discoveryElementCollection As UADiscoveryElementCollection
Try
discoveryElementCollection = client.DiscoverLocalServers("opcua.demo-this.com")
Catch uaException As UAException
Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
Exit Sub
End Try
' Display results
For Each discoveryElement As UADiscoveryElement In discoveryElementCollection
Console.WriteLine("discoveryElementCollection[""{0}""].ApplicationUriString: {1}", _
discoveryElement.DiscoveryUriString, discoveryElement.ApplicationUriString)
Next discoveryElement
' Example output:
'discoveryElementCollection["opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"].ApplicationUriString: urn:Test-PC:UA Sample Server
'discoveryElementCollection["http://opcua.demo-this.com:51211/UA/SampleServer"].ApplicationUriString: urn:Test-PC:UA Sample Server
End Sub
End Class
End Namespace
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