First experiences using QuickOPC with Free Pascal (Lazarus)
Performed with Lazarus installation package lazarus-1.6.0-fpc-3.0.0-win64.exe, on Windows 7 (x64). Later tested the pre-made code with lazarus-1.6.2-fpc-3.0.0-win64.exe, on Windows 7 (x64), and Windows 10 2015 (x64). Seen crashes when lazarus-1.6.2-fpc-3.0.0-win32.exe was used.
Lazarus downloads page is: https://www.lazarus-ide.org/index.php?page=downloads .
QuickOPC versions used: 2016.2 (5.41) "in the works", later 2018.1 (5.52) Beta.
In order to use the COM type libraries of QuickOPC, it is needed to install the LazActiveX package (comes with Lazarus). See http://wiki.freepascal.org/LazActiveX for details and instructions. Package -> Install/Uninstall Packages ..., select LazActiveX 0.1 under Available for installation, press , press . Press .
Then, use the procedures described on the LazActiveX page under TActiveXContainer early binding. Tools -> Import Type Library, select tab ActiveX References, type into the Search box, select one of our libraries (their names all start with "OPC Labs"), check Convert dependant typelibs, press . The detection of "dependant" libraries does not fully work, though - for example, OpcLabs.Baselib (OPC Labs Core Library) is not imported (the comment in the generated file says that it was not registered), therefore it is necessary to import some of the "dependant" libraries manually.
There appears to be a problem with mscorlib import, its compilation resulting in errors like "mscorlib_2_4_tlb.pas(5108,16) Error: Type "Byte" is not completely defined". Work around this by commenting out the declarations of PByte, Byte, PDouble, Double, PInt64, Int64, PSingle and Single. You need to do this in both mscorlib version imported (see further down).
After making these changes, we were getting error similar to the one below:
opclabs_easyopcua_5_41_tlb.pas(8917,13) Error: Incompatible types: got "TEvsEasyUAClientConfiguration.EventSinkInvoke(TObject;LongInt;const TGuid;LongInt;Word;tagDISPPARAMS;_Pointer;_Pointer;_Pointer);" expected "<procedure variable type of procedure(TObject;LongInt;const TGuid;LongInt;Word;tagDISPPARAMS;Pointer;Pointer;Pointer) of object;Register>"
In order to resolve it, it is necessary to go back to the code generated for mscorlib (in both of them, again), and comment out the line with declaration of Pointer, as such:
// Pointer = _Pointer;
After these changes, it should be possible to compile the .PAS code for imported type libraries. Note that due to various commonly-named types in mscorlib, be prepared that by placing that imported library into uses of your program, some types may need further qualification. For example, you may have to write SysUtils.Exception instead of simply Exception, because Exception is now also a class defined in mscorlib.
Importing OpcLabs.BaseLibForms brings in a different version of mscorlib (2.0 instead of 2.4), therefore the fixes described earlier for mscorlib must be applied to that second import as well.
A working example:
// This example shows how to read value of a single node, and display it. class procedure ReadValue.Main; var Client: EasyUAClient; Value: OleVariant; begin // Instantiate the client object Client := CoEasyUAClient.Create; Value := Client.ReadValue( 'http://opcua.demo-this.com:51211/UA/SampleServer', 'nsu=http://test.org/UA/Data/;i=10853'); WriteLn('value: ', Value); end;
Hooking COM events requires use of the TEvsXXXX wrappers, like this:
// This example shows how to subscribe to event notifications and display each // incoming event. type TClientEventHandlers2 = class procedure OnEventNotification( Sender: TObject; sender0: OleVariant; eventArgs: _EasyUAEventNotificationEventArgs); end; procedure TClientEventHandlers2.OnEventNotification( Sender: TObject; sender0: OleVariant; eventArgs: _EasyUAEventNotificationEventArgs); begin // Display the event WriteLn(eventArgs.ToString); end; class procedure SubscribeEvent.Main; var Client: EasyUAClient; EvsClient: TEvsEasyUAClient; ClientEventHandlers2: TClientEventHandlers2; begin // Instantiate the client object and hook events EvsClient := TEvsEasyUAClient.Create(nil); Client := EvsClient.ComServer; ClientEventHandlers2 := TClientEventHandlers2.Create; EvsClient.OnEventNotification := @ClientEventHandlers2.OnEventNotification; WriteLn('Subscribing...'); Client.SubscribeEvent( 'opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer', 'nsu=http://opcfoundation.org/UA/;i=2253', // UAObjectIds.Server 1000); WriteLn('Processing event notifications for 30 seconds...'); PumpSleep(30*1000); WriteLn('Unsubscribing...'); Client.UnsubscribeAllMonitoredItems; WriteLn('Waiting for 5 seconds...'); PumpSleep(5*1000); end;
Data returned in UInt64 variant do not display (or even cannot be further processed?), throw EVariantError. See e.g. __EasyUAClient.CallMethod.Main.inc.
QuickOPC works with Free Pascal (Lazarus) well - after overcoming the issues described. Examples in Free Pascal will be included with QuickOPC version 2016.2. We will have all examples for OPC UA that were present in version 5.40 for Object Pascal (Delphi), and some more.