Concepts > OPC Data Client Concepts > OPC Data Client Development Models > Imperative Programming Model > Imperative Programming Model for OPC Data (Classic and UA) > Browsing for Information (OPC Data) > Discovering OPC UA Servers > OPC UA Network Discovery |
OPC Data Client-UA allows you to obtain information about OPC UA servers from a Local Discovery Server with Multicast Extensions (LDS-ME), which uses the mDNS protocol to exchange the information about OPC UA servers with other LDS-ME-s on the network (or multiple networks).
In .NET, if you want to retrieve a list of OPC Unified Architecture servers available on your network, call the DiscoverNetworkServers method without further parameters. This will obtain the information about servers using the LDS-ME installed on the machine where the component is running, and without further restricting (filtering) them.
Further in .NET, if you want to retrieve a list of OPC Unified Architecture servers available on your network, call the DiscoverNetworkServers method with one or two arguments, passing it
In COM, the DiscoverNetworkServers method has two arguments, and therefore if you want no filtering, pass a null reference (or an empty collection) as the first argument, and pass "localhost" as the second argument if you want to use the LDS-ME installed on your machine.
In all cases described above, you will receive back a UADiscoveryElementCollection object, which is collection of UADiscoveryElement-s. Each element contains a server's discovery URL. The discovery URL is the main piece of information that you can further use if you want to connect to that OPC-UA server. Each UADiscoveryElement contains information gathered about one OPC server found by the discovery process, including things like the server name, application type, and - mainly - its DiscoveryUriString.
// This example shows how to obtain information about OPC UA servers available on the network. // The result is flat, i.e. each discovery URL is returned in separate element, with possible repetition of the servers. // // Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . // OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp . // Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own // a commercial license in order to use Online Forums, and we reply to every post. using System; using OpcLabs.EasyOpc.UA; using OpcLabs.EasyOpc.UA.Discovery; using OpcLabs.EasyOpc.UA.OperationModel; namespace UADocExamples._EasyUAClient { partial class DiscoverNetworkServers { public static void Main1() { // Instantiate the client object. var client = new EasyUAClient(); // Obtain collection of application elements. UADiscoveryElementCollection discoveryElementCollection; try { discoveryElementCollection = client.DiscoverNetworkServers("opcua.demo-this.com"); } catch (UAException uaException) { Console.WriteLine($"*** Failure: {uaException.GetBaseException().Message}"); return; } // Display results. foreach (UADiscoveryElement discoveryElement in discoveryElementCollection) { Console.WriteLine(); Console.WriteLine($"Server name: {discoveryElement.ServerName}"); Console.WriteLine($"Discovery URI string: {discoveryElement.DiscoveryUriString}"); Console.WriteLine($"Server capabilities: {discoveryElement.ServerCapabilities}"); Console.WriteLine($"Application URI string: {discoveryElement.ApplicationUriString}"); Console.WriteLine($"Product URI string: {discoveryElement.ProductUriString}"); } } } }
# This example shows how to obtain information about OPC UA servers available on the network. # The result is flat, i.e. each discovery URL is returned in separate element, with possible repetition of the servers. # # Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . # OPC client and subscriber examples in PowerShell on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-PowerShell . # Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own # a commercial license in order to use Online Forums, and we reply to every post. #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 application elements. try { $discoveryElementCollection = [IEasyUAClientExtension]::DiscoverNetworkServers($client, "opcua.demo-this.com") } catch [UAException] { Write-Host "*** Failure: $($PSItem.Exception.GetBaseException().Message)" return } # Display results. foreach ($discoveryElement in $discoveryElementCollection) { Write-Host Write-Host "Server name: $($discoveryElement.ServerName)" Write-Host "Discovery URI string: $($discoveryElement.DiscoveryUriString)" Write-Host "Server capabilities: $($discoveryElement.ServerCapabilities)" Write-Host "Application URI string: $($discoveryElement.ApplicationUriString)" Write-Host "Product URI string: $($discoveryElement.ProductUriString)" }
' This example shows how to obtain information about OPC UA servers available on the network. ' The result is flat, i.e. each discovery URL is returned in separate element, with possible repetition of the servers. ' ' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . ' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET . ' Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own ' a commercial license in order to use Online Forums, and we reply to every post. Imports OpcLabs.EasyOpc.UA Imports OpcLabs.EasyOpc.UA.Discovery Imports OpcLabs.EasyOpc.UA.OperationModel Namespace _EasyUAClient Partial Friend Class DiscoverNetworkServers Public Shared Sub Main1() ' Instantiate the client object Dim client = New EasyUAClient() ' Obtain collection of application elements Dim discoveryElementCollection As UADiscoveryElementCollection Try discoveryElementCollection = client.DiscoverNetworkServers("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() Console.WriteLine("Server name: {0}", discoveryElement.ServerName) Console.WriteLine("Discovery URI string: {0}", discoveryElement.DiscoveryUriString) Console.WriteLine("Server capabilities: {0}", discoveryElement.ServerCapabilities) Console.WriteLine("Application URI string: {0}", discoveryElement.ApplicationUriString) Console.WriteLine("Product URI string: {0}", discoveryElement.ProductUriString) Next discoveryElement End Sub End Class End Namespace
// This example shows how to obtain information about OPC UA servers available on the network. // // Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . // OPC client and subscriber examples in Object Pascal (Delphi) on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-OP . // Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own // a commercial license in order to use Online Forums, and we reply to every post. class procedure DiscoverNetworkServers.Main; var Client: OpcLabs_EasyOpcUA_TLB._EasyUAClient; Count: Cardinal; Element: OleVariant; DiscoveryElement: _UADiscoveryElement; DiscoveryElementEnumerator: IEnumVariant; DiscoveryElements: _UADiscoveryElementCollection; begin // Instantiate the client object Client := CoEasyUAClient.Create; // Obtain collection of application elements try DiscoveryElements := Client.DiscoverNetworkServers(Unassigned, 'opcua.demo-this.com'); except on E: EOleException do begin WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message])); Exit; end; end; // Display results DiscoveryElementEnumerator := DiscoveryElements.GetEnumerator; while (DiscoveryElementEnumerator.Next(1, Element, Count) = S_OK) do begin DiscoveryElement := IUnknown(Element) as _UADiscoveryElement; WriteLn; WriteLn('Server name: ', DiscoveryElement.ServerName); WriteLn('Discovery URI string: ', DiscoveryElement.DiscoveryUriString); WriteLn('Server capabilities: ', DiscoveryElement.ServerCapabilities.ToString); end; end;
// This example shows how to obtain information about OPC UA servers available on the network. // // Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . // Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own // a commercial license in order to use Online Forums, and we reply to every post. #include "stdafx.h" // Includes "QuickOpc.h", and other commonly used files #include "DiscoverNetworkServers.h" namespace _EasyUAClient { void DiscoverNetworkServers::Main() { // Initialize the COM library CoInitializeEx(NULL, COINIT_MULTITHREADED); { // Instantiate the client object _EasyUAClientPtr ClientPtr(__uuidof(EasyUAClient)); _StringCollectionPtr ServerElementFilterPtr(__uuidof(StringCollection)); _variant_t vServerElementFilter(ServerElementFilterPtr.GetInterfacePtr()); // Obtain collection of application elements _UADiscoveryElementCollectionPtr DiscoveryElementsPtr = ClientPtr->DiscoverNetworkServers(vServerElementFilter, L"opcua.demo-this.com"); // Display results IEnumVARIANTPtr EnumDiscoveryElementPtr = DiscoveryElementsPtr->GetEnumerator(); _variant_t vDiscoveryElement; while (EnumDiscoveryElementPtr->Next(1, &vDiscoveryElement, NULL) == S_OK) { _UADiscoveryElementPtr DiscoveryElementPtr(vDiscoveryElement); _tprintf(_T("\n")); _tprintf(_T("Application type: %d\n"), DiscoveryElementPtr->ApplicationType); _tprintf(_T("Server name: %s\n"), (LPCTSTR)CW2CT(DiscoveryElementPtr->ServerName)); _tprintf(_T("Discovery URI string: %s\n"), (LPCTSTR)CW2CT(DiscoveryElementPtr->DiscoveryUriString)); _tprintf(_T("Server capabilities: ")); IEnumVARIANTPtr EnumServerCapabilityPtr = DiscoveryElementPtr->ServerCapabilities->GetEnumerator(); _variant_t vServerCapability = NULL; while (EnumServerCapabilityPtr->Next(1, &vServerCapability, NULL) == S_OK) _tprintf(_T("%s "), (LPCTSTR)CW2CT(_bstr_t(vServerCapability))); _tprintf(_T("\n")); vDiscoveryElement.Clear(); } } // Release all interface pointers BEFORE calling CoUninitialize() CoUninitialize(); } }
REM This example shows how to obtain information about OPC UA servers available on the network. REM REM Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . REM OPC client and subscriber examples in Visual Basic on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VB . REM Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own REM a commercial license in order to use Online Forums, and we reply to every post. Public Sub DiscoverNetworkServers_Main_Command_Click() OutputText = "" ' Instantiate the client object Dim Client As New EasyUAClient ' Obtain collection of application elements On Error Resume Next Dim DiscoveryElementCollection As UADiscoveryElementCollection Set DiscoveryElementCollection = Client.DiscoverNetworkServers(Nothing, "opcua.demo-this.com") If Err.Number <> 0 Then OutputText = OutputText & "*** Failure: " & Err.Source & ": " & Err.Description & vbCrLf Exit Sub End If On Error GoTo 0 ' Display results Dim DiscoveryElement As UADiscoveryElement: For Each DiscoveryElement In DiscoveryElementCollection OutputText = OutputText & vbCrLf OutputText = OutputText & "Server name: " & DiscoveryElement.ServerName & vbCrLf OutputText = OutputText & "Discovery URI string: " & DiscoveryElement.DiscoveryUriString & vbCrLf OutputText = OutputText & "Server capabilities: " & DiscoveryElement.serverCapabilities.ToString & vbCrLf Next End Sub
Rem This example shows how to obtain information about OPC UA servers available on the network. Rem Rem Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . Rem OPC client and subscriber examples in VBScript on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBScript . Rem Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own Rem a commercial license in order to use Online Forums, and we reply to every post. Option Explicit ' Instantiate the client object Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.UA.EasyUAClient") ' Obtain collection of application elements On Error Resume Next Dim DiscoveryElementCollection: Set DiscoveryElementCollection = _ Client.DiscoverNetworkServers(Nothing, "opcua.demo-this.com") If Err.Number <> 0 Then WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description WScript.Quit End If On Error Goto 0 ' Display results Dim DiscoveryElement: For Each DiscoveryElement In DiscoveryElementCollection WScript.Echo WScript.Echo "Server name: " & DiscoveryElement.ServerName WScript.Echo "Discovery URI string: " & DiscoveryElement.DiscoveryUriString Dim s: s = "" Dim serverCapability: For Each serverCapability In DiscoveryElement.ServerCapabilities s = s & serverCapability & " " Next WScript.Echo "Server capabilities: " & s Next
# This example shows how to obtain information about OPC UA servers available on the network. # The result is flat, i.e. each discovery URL is returned in separate element, with possible repetition of the servers. # # 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 . # Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own # a commercial license in order to use Online Forums, and we reply to every post. # 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.Discovery import * from OpcLabs.EasyOpc.UA.OperationModel import * # Instantiate the client object. client = EasyUAClient() # Obtain collection of application elements. try: discoveryElementCollection = IEasyUAClientExtension.DiscoverNetworkServers(client, 'opcua.demo-this.com') except UAException as uaException: print('*** Failure: ' + uaException.GetBaseException().Message) exit() # Display results. for discoveryElement in discoveryElementCollection: print() print('Server name: ', discoveryElement.ServerName, sep='') print('Discovery URI string: ', discoveryElement.DiscoveryUriString, sep='') print('Server capabilities: ', discoveryElement.ServerCapabilities, sep='') print('Application URI string: ', discoveryElement.ApplicationUriString, sep='') print('Product URI string: ', discoveryElement.ProductUriString, sep='') print() print('Finished.')
You can also obtain the results unflattened:
// This example shows how to obtain information about OPC UA servers available on the network. // The result is hierarchical, i.e. each server is returned in one element, and the element contains all its discovery URLs. // // Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . // OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp . // Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own // a commercial license in order to use Online Forums, and we reply to every post. using System; using OpcLabs.EasyOpc.UA; using OpcLabs.EasyOpc.UA.Discovery; using OpcLabs.EasyOpc.UA.OperationModel; namespace UADocExamples._EasyUAClient { partial class DiscoverNetworkServers { public static void Hierarchical() { // Instantiate the client object var client = new EasyUAClient(); // Obtain collection of application elements UADiscoveryElementCollection discoveryElementCollection; try { discoveryElementCollection = client.DiscoverNetworkServers("opcua.demo-this.com", flat:false); } catch (UAException uaException) { Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message); return; } // Display results foreach (UADiscoveryElement discoveryElement in discoveryElementCollection) { Console.WriteLine(); Console.WriteLine("Server name: {0}", discoveryElement.ServerName); Console.WriteLine("Discovery URI strings:"); foreach (string discoveryUriString in discoveryElement.DiscoveryUriStrings) Console.WriteLine(" {0}", discoveryUriString); Console.WriteLine("Server capabilities: {0}", discoveryElement.ServerCapabilities); } } } }
' This example shows how to obtain information about OPC UA servers available on the network. ' The result is hierarchical, i.e. each server is returned in one element, and the element contains all its discovery URLs. ' ' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . ' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET . ' Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own ' a commercial license in order to use Online Forums, and we reply to every post. Imports OpcLabs.EasyOpc.UA Imports OpcLabs.EasyOpc.UA.Discovery Imports OpcLabs.EasyOpc.UA.OperationModel Namespace _EasyUAClient Partial Friend Class DiscoverNetworkServers Public Shared Sub Hierarchical() ' Instantiate the client object Dim client = New EasyUAClient() ' Obtain collection of application elements Dim discoveryElementCollection As UADiscoveryElementCollection Try discoveryElementCollection = client.DiscoverNetworkServers("opcua.demo-this.com", flat:=False) 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() Console.WriteLine("Server name: {0}", discoveryElement.ServerName) Console.WriteLine("Discovery URI strings:") For Each discoveryUriString As String In discoveryElement.DiscoveryUriStrings Console.WriteLine(" {0}", discoveryUriString) Next discoveryUriString Console.WriteLine("Server capabilities: {0}", discoveryElement.ServerCapabilities) Next discoveryElement End Sub End Class End Namespace
# This example shows how to obtain information about OPC UA servers available on the network. # The result is hierarchical, i.e. each server is returned in one element, and the element contains all its discovery # URLs. # # 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 . # Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own # a commercial license in order to use Online Forums, and we reply to every post. # 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.Discovery import * from OpcLabs.EasyOpc.UA.OperationModel import * # Instantiate the client object. client = EasyUAClient() # Obtain collection of application elements. try: discoveryElementCollection = IEasyUAClientExtension.DiscoverNetworkServers(client, 'opcua.demo-this.com', False) # flat=False except UAException as uaException: print('*** Failure: ' + uaException.GetBaseException().Message) exit() # Display results. for discoveryElement in discoveryElementCollection: print() print('Server name: ', discoveryElement.ServerName, sep='') print('Discovery URI strings:') for discoveryUriString in discoveryElement.DiscoveryUriStrings: print(' ', discoveryUriString, sep='') print('Server capabilities: ', discoveryElement.ServerCapabilities, sep='') print() print('Finished.')
Note that QuickOPC returns UADiscoveryElementCollection from all OPC UA discovery methods, but the amount of information contained in each returned UADiscoveryElement depends on the discovery approach used. For OPC UA Global Discovery and OPC UA Network Discovery, only following primary properties of each UADiscoveryElement are filled in:
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