// This example shows how to subscribe to changes of a single item and display the value of the item with each change.
type
TSubscribeItem_ClientEventHandlers = class
// Item changed event handler
procedure OnItemChanged(
ASender: TObject;
sender: OleVariant;
const eventArgs: _EasyDAItemChangedEventArgs);
end;
procedure TSubscribeItem_ClientEventHandlers.OnItemChanged(
ASender: TObject;
sender: OleVariant;
const eventArgs: _EasyDAItemChangedEventArgs);
begin
if eventArgs.Succeeded then
WriteLn(eventArgs.Vtq.ToString)
else
WriteLn(Format('*** Failure: %s', [eventArgs.ErrorMessageBrief]));
end;
class procedure SubscribeItem.Main;
var
Client: TEasyDAClient;
ClientEventHandlers: TSubscribeItem_ClientEventHandlers;
begin
// Instantiate the client object and hook events
Client := TEasyDAClient.Create(nil);
ClientEventHandlers := TSubscribeItem_ClientEventHandlers.Create;
Client.OnItemChanged := ClientEventHandlers.OnItemChanged;
Client.SubscribeItem('', 'OPCLabs.KitServer.2', 'Simulation.Random', 1000);
WriteLn('Processing item changed events for 1 minute...');
PumpSleep(60*1000);
WriteLn('Unsubscribing...');
Client.UnsubscribeAllItems;
WriteLn('Waiting for 5 seconds...');
PumpSleep(5*1000);
WriteLn('Finished.');
FreeAndNil(Client);
FreeAndNil(ClientEventHandlers);
end;
// This example shows how to subscribe to changes of a single item and display the value of the item with each change.
//
// Some related documentation: http://php.net/manual/en/function.com-event-sink.php . Pay attention to the comment that says
// "Be careful how you use this feature; if you are doing something similar to the example below, then it doesn't really make
// sense to run it in a web server context.". What they are trying to say is that processing a web request should be
// a short-lived code, which does not fit well with the idea of being subscribed to events and received them over longer time.
// It is possible to write such code, but it is only useful when processing the request is allowed to take relatively long. Or,
// when you are using PHP from command-line, or otherwise - not to serve a web page directly.
//
// Subscribing to QuickOPC-COM events in the context of PHP Web application, while not imposing the limitations to the request
// processing time, has to be "worked around", e.g. using the "event pull" mechanism.
class DEasyDAClientEvents {
function ItemChanged($varSender, $varE)
{
if ($varE->Succeeded)
{
print $varE->Vtq->ToString();
print "\n";
}
else
{
printf("*** Failure: %s\n", $varE->ErrorMessageBrief);
}
}
}
$Client = new COM("OpcLabs.EasyOpc.DataAccess.EasyDAClient");
$Events = new DEasyDAClientEvents();
com_event_sink($Client, $Events, "DEasyDAClientEvents");
$Client->SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000);
print "Processing item changed events for 1 minute...\n";
$startTime = time(); do { com_message_pump(1000); } while (time() < $startTime + 60);
Rem This example shows how to subscribe to changes of a single item and display the value of the item with each change.
' The client object, with events
'Public WithEvents Client1 As EasyDAClient
Private Sub SubscribeItem_Main_Command_Click()
OutputText = ""
' Instantiate the client object and hook events
Set Client1 = New EasyDAClient
OutputText = OutputText & "Subscribing..." & vbCrLf
Call Client1.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000)
OutputText = OutputText & "Processing item changed events for 1 minute..." & vbCrLf
Pause 60000
OutputText = OutputText & "Unsubscribing..." & vbCrLf
Client1.UnsubscribeAllItems
OutputText = OutputText & "Waiting for 5 seconds..." & vbCrLf
Pause 5000
OutputText = OutputText & "Finished." & vbCrLf
Set Client1 = Nothing
End Sub
Public Sub Client1_ItemChanged(ByVal sender As Variant, ByVal eventArgs As EasyDAItemChangedEventArgs)
If eventArgs.Succeeded Then
OutputText = OutputText & eventArgs.vtq & vbCrLf
Else
OutputText = OutputText & "*** Failure: " & eventArgs.ErrorMessageBrief & vbCrLf
End If
End Sub
Rem This example shows how to subscribe to changes of a single item and display the value of the item with each change.
Option Explicit
Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")
WScript.ConnectObject Client, "Client_"
Client.SubscribeItem "", "OPCLabs.KitServer.2", "Simulation.Random", 1000
WScript.Echo "Processing item changed events for 1 minute..."
WScript.Sleep 60*1000
Sub Client_ItemChanged(Sender, e)
If Not (e.Succeeded) Then
WScript.Echo "*** Failure: " & e.ErrorMessageBrief
Exit Sub
End If
WScript.Echo e.Vtq.ToString
End Sub
