Lesson 5: Calling Methods

Content:

• Step 1: Implementing Call

Step 1: Implementing Call

Add the following code to header,

/* OPC UA service calls */ 
void callMethod();

and source file, rsp.:

void callMethod()
{
    printf("\n\n****************************************************************\n");
    printf("** Try to call a method\n");
    if ( g_pUaSession == NULL )
    {
        printf("** Error: Server not connected\n");
        printf("****************************************************************\n");
        return;
    }

    UaStatus           status;
    CallIn             callRequest;
    CallOut            callResult;
    UaVariant          vTemp;
    ServiceSettings    serviceSettings;

    g_ObjectNodeIds.create(1);
    g_MethodNodeIds.create(1);
    
    g_ObjectNodeIds[0].setNodeId( OBJECT_STRING_NODEID, NAMESPACE_INDEX );
    g_MethodNodeIds[0].setNodeId( METHOD_STRING_NODEID, NAMESPACE_INDEX );   
    
    callRequest.objectId = g_ObjectNodeIds[0];
    callRequest.methodId = g_MethodNodeIds[0];

    /* Used for Methods with arguments
    callRequest.inputArguments.create(2);
    // Set Temperature Set Point
    vTemp.setDouble(60);
    vTemp.copyTo(&callRequest.inputArguments[0]);
    // Set Humitidy Set Point
    vTemp.setDouble(50);
    vTemp.copyTo(&callRequest.inputArguments[1]);*/

    /********************************************************************* 
     Call Method 
    **********************************************************************/
    status = g_pUaSession->call(
        serviceSettings,    // Use default settings
        callRequest,        // In parameters and settings for the method call
        callResult);        // Out parameters and results returned from the method call
    /*********************************************************************/
    if ( status.isBad() )
    {
        printf("** Error: UaSession::call failed [ret=%s] *********\n", status.toString().toUtf8());
    }
    else
    {
        printf("** Error: UaSession::call succeeded!\n");
    }
    printf("****************************************************************\n");
}

call() calls the actual UaSession::call() in order to call a particular Method which belongs to a particular Object. UaSession::call() takes the following parameters:

• serviceSettings: the general Service settings like timeout,
• callRequest: the Object and Method to call and input arguments ( if necessary ),
• callResult: the output arguments and input argument results.

Complete header

Add

/* Globals */ 
UaSession*                              g_pUaSession;
Callback*                               g_pCallback;
UaObjectArray<UaNodeId>                 g_VariableNodeIds;
UaObjectArray<UaNodeId>                 g_WriteVariableNodeIds;
// ++
UaObjectArray<UaNodeId>                 g_ObjectNodeIds;
UaObjectArray<UaNodeId>                 g_MethodNodeIds;
// ++

to header.

Add define

Add

 . . .

// ServerURL
#define SERVER_URL                                  "opc.tcp://localhost:4841"    
// ++ 
// NodeIds for a method call
#define OBJECT_STRING_NODEID                        "AirConditioner_2"
#define METHOD_STRING_NODEID                        "AirConditioner_2.Stop"
// Namespace
#define NAMESPACE_INDEX                             2
#define NAMESPACE_URI                               "MyUaServer/BuildingAutomation"
// ++

 . . .

to source file.

Complete main()

Add

/********************************************************************* 
 Call Method 
**********************************************************************/
callMethod();
/*********************************************************************/

to main().