Raised for a change in the condition of an OPC server.
Event Data
The event handler receives an argument of type EasyUAServerConditionChangedEventArgs containing data related to this event. The following EasyUAServerConditionChangedEventArgs properties provide information specific to this event.
Example
.NET
// This example shows how to monitor connections to and disconnections from the OPC UA server.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
using System;
using Microsoft.Extensions.DependencyInjection;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.OperationModel;
using OpcLabs.EasyOpc.UA.Services;
namespace UADocExamples._EasyUAClientConnectionMonitoring
{
class ServerConditionChanged
{
public static void Main1()
{
UAEndpointDescriptor endpointDescriptor =
"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
// or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
// or "https://opcua.demo-this.com:51212/UA/SampleServer/"
// Instantiate the client object.
using (var client = new EasyUAClient())
{
// Obtain the client connection monitoring service.
IEasyUAClientConnectionMonitoring clientConnectionMonitoring = client.GetService<IEasyUAClientConnectionMonitoring>();
if (clientConnectionMonitoring is null)
{
Console.WriteLine("The client connection monitoring service is not available.");
return;
}
// Hook events.
client.DataChangeNotification += client_DataChangeNotification;
clientConnectionMonitoring.ServerConditionChanged += clientConnectionMonitoring_OnServerConditionChanged;
try
{
Console.WriteLine("Reading (1)");
// The first read will cause a connection to the server.
UAAttributeData attributeData1 = client.Read(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853");
Console.WriteLine(attributeData1);
Console.WriteLine("Reading (2)");
// The second read, because it closely follows the first one, will reuse the connection that is already
// open.
UAAttributeData attributeData2 = client.Read(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853");
Console.WriteLine(attributeData2);
}
catch (UAException uaException)
{
Console.WriteLine($"*** Failure: {uaException.GetBaseException().Message}");
}
Console.WriteLine("Waiting for 10 seconds...");
// Since the connection is now not used for some time, it will be closed.
System.Threading.Thread.Sleep(10 * 1000);
Console.WriteLine("Subscribing...");
// Subscribing to a monitored item will cause a connection to the server, if one is not yet open.
client.SubscribeDataChange(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 1000);
Console.WriteLine("Waiting for 10 seconds...");
// The connection will not be closed as long as there are any subscriptions to the server.
System.Threading.Thread.Sleep(10 * 1000);
Console.WriteLine("Unsubscribing...");
client.UnsubscribeAllMonitoredItems();
Console.WriteLine("Waiting for 10 seconds...");
// After some delay, the connection will be closed, because there are no subscriptions to the server.
System.Threading.Thread.Sleep(10 * 1000);
Console.WriteLine("Finished.");
}
}
static void client_DataChangeNotification(object sender, EasyUADataChangeNotificationEventArgs e)
{
// Display value
if (e.Succeeded)
Console.WriteLine($"Value: {e.AttributeData.Value}");
else
Console.WriteLine($"*** Failure: {e.ErrorMessageBrief}");
}
static void clientConnectionMonitoring_OnServerConditionChanged(object sender, EasyUAServerConditionChangedEventArgs e)
{
// Display the event
Console.WriteLine(e);
}
// Example output:
//
//Reading(1)
//"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connecting; Success
//"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connected; Success
//-8.095801E+32 {System.Single} @2021-06-24T07:09:46.062 @@2021-06-24T07:09:46.062; Good
//Reading(2)
//-3.11389E-18 {System.Single} @2021 - 06 - 24T07: 09:46.125 @@2021 - 06 - 24T07: 09:46.125; Good
//Waiting for 10 seconds...
//"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnecting; Success
//"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnected(Infinite); Success
//Subscribing...
//"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connecting; Success
//Waiting for 10 seconds...
//"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connected; Success
//Value: 3.293034E-31
//Value: 6.838126E+37
//Value: 5.837702E-29
//Value: 0.02940081
//Value: -9.653872E-17
//Value: -1.012749E+29
//Value: -1.422391E+20
//Value: -3.56571E-22
//Unsubscribing...
//Waiting for 10 seconds...
//"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnecting; Success
//"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnected(Infinite); Success
//Finished.
}
}
# This example shows how to monitor connections to and disconnections from the OPC UA server.
#
# 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 time
# Import .NET namespaces.
from Microsoft.Extensions.DependencyInjection import *
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.OperationModel import *
from OpcLabs.EasyOpc.UA.Services import *
def dataChangeNotification(sender, e):
# Display value.
if e.Succeeded:
print('Value: ', e.AttributeData.Value, sep='')
else:
print('*** Failure: ', e.ErrorMessageBrief, sep='')
def onServerConditionChanged(sender, e):
# Display the event.
print(e)
endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:51210/UA/SampleServer')
# or 'http://opcua.demo-this.com:51211/UA/SampleServer' (currently not supported)
# or 'https://opcua.demo-this.com:51212/UA/SampleServer/'
# Instantiate the client object.
client = None
try:
client = EasyUAClient()
# Obtain the client connection monitoring service.
clientConnectionMonitoring = ServiceProviderServiceExtensions.GetService[IEasyUAClientConnectionMonitoring](client)
if clientConnectionMonitoring is None:
print('The client connection monitoring service is not available.')
exit()
# Hook events
client.DataChangeNotification += dataChangeNotification
clientConnectionMonitoring.ServerConditionChanged += onServerConditionChanged
try:
print('Reading (1)')
# The first read will cause a connection to the server.
attributeData1 = IEasyUAClientExtension.Read(client,
endpointDescriptor,
UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'))
print(attributeData1)
print('Reading (2)')
# The second read, because it closely follows the first one, will reuse the connection that is already
# open.
attributeData2 = IEasyUAClientExtension.Read(client,
endpointDescriptor,
UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'))
print(attributeData2)
except UAException as uaException:
print('*** Failure: ' + uaException.GetBaseException().Message)
print('Waiting for 10 seconds...')
# Since the connection is now not used for some time, it will be closed.
time.sleep(10)
print('Subscribing...')
# Subscribing to a monitored item will cause a connection to the server, if one is not yet open.
IEasyUAClientExtension.SubscribeDataChange(client,
endpointDescriptor,
UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'),
1000)
print('Waiting for 10 seconds...')
# The connection will not be closed as long as there are any subscriptions to the server.
time.sleep(10)
print('Unsubscribing...')
client.UnsubscribeAllMonitoredItems()
print('Waiting for 10 seconds...')
# After some delay, the connection will be closed, because there are no subscriptions to the server.
time.sleep(10)
print('Finished.')
finally:
client and client.Dispose()
' This example shows how to monitor connections to and disconnections from the OPC UA server.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
Imports Microsoft.Extensions.DependencyInjection
Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.OperationModel
Imports OpcLabs.EasyOpc.UA.Services
Namespace _EasyUAClientConnectionMonitoring
Partial Friend Class ServerConditionChanged
Public Shared Sub Main1()
Dim endpointDescriptor As UAEndpointDescriptor =
"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
' or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
' or "https://opcua.demo-this.com:51212/UA/SampleServer/"
' Instantiate the client object.
Using client = New EasyUAClient()
' Obtain the client connection monitoring service.
Dim clientConnectionMonitoring As IEasyUAClientConnectionMonitoring = client.GetService(Of IEasyUAClientConnectionMonitoring)
If clientConnectionMonitoring Is Nothing Then
Console.WriteLine("The client connection monitoring service is not available.")
Exit Sub
End If
' Hook events.
AddHandler client.DataChangeNotification, AddressOf client_DataChangeNotification
AddHandler clientConnectionMonitoring.ServerConditionChanged, AddressOf clientConnectionMonitoring_OnServerConditionChanged
Try
Console.WriteLine("Reading (1)")
' The first read will cause a connection to the server.
Dim attributeData1 As UAAttributeData = client.Read(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853")
Console.WriteLine(attributeData1)
Console.WriteLine("Reading (2)")
' The second read, because it closely follows the first one, will reuse the connection that is already
' open.
Dim attributeData2 As UAAttributeData = client.Read(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853")
Console.WriteLine(attributeData2)
Catch uaException As UAException
Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message)
End Try
Console.WriteLine("Waiting for 10 seconds...")
' Since the connection is now Not used for some time, it will be closed.
System.Threading.Thread.Sleep(10 * 1000)
Console.WriteLine("Subscribing...")
' Subscribing to a monitored item will cause a connection to the server, if one is not yet open.
client.SubscribeDataChange(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 1000)
Console.WriteLine("Waiting for 10 seconds...")
' The connection will not be closed as long as there are any subscriptions to the server.
System.Threading.Thread.Sleep(10 * 1000)
Console.WriteLine("Unsubscribing...")
client.UnsubscribeAllMonitoredItems()
Console.WriteLine("Waiting for 10 seconds...")
' After some delay, the connection will be closed, because there are no subscriptions to the server.
System.Threading.Thread.Sleep(10 * 1000)
Console.WriteLine("Finished.")
End Using
End Sub
Private Shared Sub client_DataChangeNotification(ByVal sender As Object, ByVal e As EasyUADataChangeNotificationEventArgs)
' Display value
If e.Succeeded Then
Console.WriteLine($"Value: {e.AttributeData.Value}")
Else
Console.WriteLine($"*** Failure: {e.ErrorMessageBrief}")
End If
End Sub
Private Shared Sub clientConnectionMonitoring_OnServerConditionChanged(ByVal sender As Object, ByVal e As EasyUAServerConditionChangedEventArgs)
' Display the event
Console.WriteLine(e)
End Sub
' Example output
'
'Reading(1)
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connecting; Success
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connected; Success
'-8.095801E+32 {System.Single} @2021-06-24T07:09:46.062 @@2021-06-24T07:09:46.062; Good
'Reading(2)
'-3.11389E-18 {System.Single} @2021 - 06 - 24T07: 09:46.125 @@2021 - 06 - 24T07: 09:46.125; Good
'Waiting for 10 seconds...
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnecting; Success
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnected(Infinite); Success
'Subscribing...
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connecting; Success
'Waiting for 10 seconds...
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Connected; Success
'Value: 3.293034E-31
'Value: 6.838126E+37
'Value: 5.837702E-29
'Value: 0.02940081
'Value: -9.653872E-17
'Value: -1.012749E+29
'Value: -1.422391E+20
'Value: -3.56571E-22
'Unsubscribing...
'Waiting for 10 seconds...
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnecting; Success
'"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer" Disconnected(Infinite); Success
'Finished.
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