Simple OPC Client

SimpleOPCClient_v2.cpp

////////////////////////////////////////////////////////////////////////
// project: SimpleOPCClient
// version: 2 
//
// subject: this is a simple OPC Client that read the value of an item
// from an OPC server.
//
// file: SimpleOPCClient.cpp
//
// writer: Philippe GRAS - CERN / EP
//
//http://lhcb-online.web.cern.ch/lhcb-online/ecs/opcevaluation/opcclienttutorial/SimpleClient.html

#include <atlbase.h>
#include <objbase.h>
#include <iostream>
#include "opc.h"
#include "SimpleOPCClient.h"
#include "opc_i.c"

using namespace std;

#define OPC_SERVER_NAME L"OPC.Evaluation:HV supply.1" // e.g.: L"OPC.Evaluation:HV supply.1"
#define ITEM_ID L"cr02.ch00.V0"
#define VT VT_R4
#define XVAL fltVal

//#define REMOTE_SERVER_NAME L"your_path"

//////////////////////////////////////////////////////////////////////
// Read the value of an item on an OPC server. 
//
void main(void)
{
	IOPCServer* pIOPCServer = NULL;   //pointer to IOPServer interface
	IOPCItemMgt* pIOPCItemMgt = NULL; //pointer to IOPCItemMgt interface

	OPCHANDLE hServerGroup; // server handle to the group
	OPCHANDLE hServerItem;  // server handle to the item


	// have to be done before using microsoft COM library:
	CoInitialize(NULL);

	// Let's instantiante the IOPCServer interface and get a pointer of it:
	pIOPCServer = InstantiateServer(OPC_SERVER_NAME);

	// Add the OPC group the OPC server and get an handle to the IOPCItemMgt
	//interface:
	AddTheGroup(pIOPCServer, pIOPCItemMgt, hServerGroup);

	// Add the OPC item
    AddTheItem(pIOPCItemMgt, hServerItem);

	//Read the value of the item from device:
	VARIANT varValue; //to stor the read value
	VariantInit(&varValue);
	ReadItem(pIOPCItemMgt, hServerItem, varValue);

	// print the read value:
	cout << "Read value: " << varValue.XVAL << endl;

	// Remove the OPC item:
	RemoveItem(pIOPCItemMgt, hServerItem);

	// Remove the OPC group: 
    RemoveGroup(pIOPCServer, hServerGroup);

	// release the interface references:
	pIOPCItemMgt->Release();
	pIOPCServer->Release();

	//close the COM library:
	CoUninitialize();
}

////////////////////////////////////////////////////////////////////
// Instantiate the IOPCServer interface of the OPCServer
// having the name ServerName. Return a pointer to this interface
//
IOPCServer* InstantiateServer(wchar_t ServerName[])
{
	CLSID CLSID_OPCServer;
	HRESULT hr;

	// get the CLSID from the OPC Server Name:
	hr = CLSIDFromString(ServerName, &CLSID_OPCServer);
	_ASSERT(!FAILED(hr));


	//queue of the class instances to create
	LONG cmq = 1; // nbr of class instance to create.
	MULTI_QI queue[1] =
		{{&IID_IOPCServer,
		NULL,
		0}};

	//Server info:
	//COSERVERINFO CoServerInfo =
    //{
	//	/*dwReserved1*/ 0,
	//	/*pwszName*/ REMOTE_SERVER_NAME,
	//	/*COAUTHINFO*/  NULL,
	//	/*dwReserved2*/ 0
    //}; 

	// create an instance of the IOPCServer
	hr = CoCreateInstanceEx(CLSID_OPCServer, NULL, CLSCTX_SERVER,
		/*&CoServerInfo*/NULL, cmq, queue);
	_ASSERT(!hr);

	// return a pointer to the IOPCServer interface:
	return(IOPCServer*) queue[0].pItf;
}


/////////////////////////////////////////////////////////////////////
// Add group "Group1" to the Server whose IOPCServer interface
// is pointed by pIOPCServer. 
// Returns a pointer to the IOPCItemMgt interface of the added group
// and a server opc handle to the added group.
//
void AddTheGroup(IOPCServer* pIOPCServer, IOPCItemMgt* &pIOPCItemMgt, 
				 OPCHANDLE& hServerGroup)
{
	DWORD dwUpdateRate = 0;
	OPCHANDLE hClientGroup = 0;

	// Add an OPC group and get a pointer to the IUnknown I/F:
    HRESULT hr = pIOPCServer->AddGroup(/*szName*/ L"Group1",
		/*bActive*/ FALSE,
		/*dwRequestedUpdateRate*/ dwUpdateRate,
		/*hClientGroup*/ hClientGroup,
		/*pTimeBias*/ 0,
		/*pPercentDeadband*/ 0,
		/*dwLCID*/0,
		/*phServerGroup*/&hServerGroup,
		&dwUpdateRate,
		/*riid*/ IID_IOPCItemMgt,
		/*ppUnk*/ (IUnknown**) &pIOPCItemMgt);
	_ASSERT(!FAILED(hr));
}



//////////////////////////////////////////////////////////////////
// Add the Item ITEM_ID to the group whose IOPCItemMgt interface
// is pointed by pIOPCItemMgt pointer. Return a server opc handle
// to the item.
 
void AddTheItem(IOPCItemMgt* pIOPCItemMgt, OPCHANDLE& hServerItem)
{
	HRESULT hr;

	// Array of items to add:
	OPCITEMDEF ItemArray[1] =
	{{
	/*szAccessPath*/ L"",
	/*szItemID*/ ITEM_ID,
	/*bActive*/ FALSE,
	/*hClient*/ 1,
	/*dwBlobSize*/ 0,
	/*pBlob*/ NULL,
	/*vtRequestedDataType*/ VT,
	/*wReserved*/0
	}};

	//Add Result:
	OPCITEMRESULT* pAddResult=NULL;
	HRESULT* pErrors = NULL;

	// Add an Item to the previous Group:
	hr = pIOPCItemMgt->AddItems(1, ItemArray, &pAddResult, &pErrors);
	_ASSERT(!hr);

	// Server handle for the added item:
	hServerItem = pAddResult[0].hServer;

	// release memory allocated by the server:
	CoTaskMemFree(pAddResult->pBlob);

	CoTaskMemFree(pAddResult);
	pAddResult = NULL;

	CoTaskMemFree(pErrors);
	pErrors = NULL;
}

///////////////////////////////////////////////////////////////////////////////
// Read from device the value of the item having the "hServerItem" server 
// handle and belonging to the group whose one interface is pointed by
// pGroupIUnknown. The value is put in varValue. 
//
void ReadItem(IUnknown* pGroupIUnknown, OPCHANDLE hServerItem, VARIANT& varValue)
{
	// value of the item:
	OPCITEMSTATE* pValue = NULL;

	//get a pointer to the IOPCSyncIOInterface:
	IOPCSyncIO* pIOPCSyncIO;
	pGroupIUnknown->QueryInterface(__uuidof(pIOPCSyncIO), (void**) &pIOPCSyncIO);

	// read the item value from the device:
	HRESULT* pErrors = NULL; //to store error code(s)
	HRESULT hr = pIOPCSyncIO->Read(OPC_DS_DEVICE, 1, &hServerItem, &pValue, &pErrors);
	_ASSERT(!hr);
	_ASSERT(pValue!=NULL);

	varValue = pValue[0].vDataValue;

	//Release memeory allocated by the OPC server:
	CoTaskMemFree(pErrors);
	pErrors = NULL;

	CoTaskMemFree(pValue);
	pValue = NULL;

	// release the reference to the IOPCSyncIO interface:
	pIOPCSyncIO->Release();
}


///////////////////////////////////////////////////////////////////////////
// Remove the item whose server handle is hServerItem from the group
// whose IOPCItemMgt interface is pointed by pIOPCItemMgt
//
void RemoveItem(IOPCItemMgt* pIOPCItemMgt, OPCHANDLE hServerItem)
{
	// server handle of items to remove:
	OPCHANDLE hServerArray[1];
	hServerArray[0] = hServerItem;
	
	//Remove the item:
	HRESULT* pErrors; // to store error code(s)
	HRESULT hr = pIOPCItemMgt->RemoveItems(1, hServerArray, &pErrors);
	_ASSERT(!hr);

	//release memory allocated by the server:
	CoTaskMemFree(pErrors);
	pErrors = NULL;
}


////////////////////////////////////////////////////////////////////////
// Remove the Group whose server handle is hServerGroup from the server
// whose IOPCServer interface is pointed by pIOPCServer
//
void RemoveGroup (IOPCServer* pIOPCServer, OPCHANDLE hServerGroup)
{
	// Remove the group:
	HRESULT hr = pIOPCServer->RemoveGroup(hServerGroup, FALSE);
	_ASSERT(!hr);
}

SimpleOPCClient_v2.h

////////////////////////////////////////////////////////////////////////
// project: SimpleOPCClient
// version: 2 
//
// subject: this is a simple OPC Client that read the value of an item
// from an OPC server.
//
// file: SimpleOPCClient.h
//
// writer: Philippe GRAS - CERN / EP
//




#ifndef SIMPLE_OPC_CLIENT_H
#define SIMPLE_OPC_CLIENT_H

IOPCServer* InstantiateServer(wchar_t ServerName[]);
void AddTheGroup(IOPCServer* pIOPCServer, IOPCItemMgt* &pIOPCItemMgt, 
				 OPCHANDLE& hServerGroup);
void AddTheItem(IOPCItemMgt* pIOPCItemMgt, OPCHANDLE& hServerItem);
void ReadItem(IUnknown* pGroupIUnknown, OPCHANDLE hServerItem, VARIANT& varValue);
void RemoveItem(IOPCItemMgt* pIOPCItemMgt, OPCHANDLE hServerItem);
void RemoveGroup (IOPCServer* pIOPCServer, OPCHANDLE hServerGroup);

#endif // SIMPLE_OPC_CLIENT_H not defined