Supplement C: Registering Nodes

Content:

• Step 1: Implementing registerNodes()
• Step 2: Implementing unregisterNodes()

Due to the fact that Read and Write are called with NodeIds, not with handles like in COM DA, UaSession provides registerNodes() to allow a client to optimize the cyclic access to Nodes for example for writing variable values or for calling methods.

Step 1: Implementing registerNodes()

Add the following code to header,

/* OPC UA service calls */ 

. . .
 
void registerNodes();

and source file, rsp.:

/*============================================================================
   registerNodes - RegisterNodes for frequently use in read or write
 *===========================================================================*/
void registerNodes()
{
    printf("\n\n****************************************************************\n");
    printf("** Try to call registerNodes for configured node ids\n");
    if ( g_pUaSession == NULL )
    {
        printf("** Error: Server not connected\n");
        printf("****************************************************************\n");
        return;
    }

    OpcUa_UInt32      i;
    OpcUa_UInt32      count;
    UaStatus          status;
    UaNodeIdArray     nodesToRegister;
    UaNodeIdArray     registeredNodes;
    ServiceSettings   serviceSettings;

    // Initialize IN parameter nodesToRegister 
    count = g_VariableNodeIds.length();
    nodesToRegister.create(count);
    for ( i=0; i<count; i++ )
    {
        g_VariableNodeIds[i].copyTo(&nodesToRegister[i]);
    }

    /********************************************************************* 
     Call registerNodes service 
    **********************************************************************/
    status = g_pUaSession->registerNodes(
        serviceSettings,     // Use default settings
        nodesToRegister,     // Array of nodeIds to register
        registeredNodes);    // Returns an array of registered nodeIds
    /*********************************************************************/
    if ( status.isBad() )
    {
        printf("** Error: UaSession::registerNodes failed [ret=%s] **\n", status.toString().toUtf8());
    }
    else
    {
        printf("** UaSession::registerNodes succeeded\n");
        for ( i=0; i<count; i++ )
        {
            // Copy back returned NodeIds
            g_VariableNodeIds[i] = registeredNodes[i];
        }
        printf("****************************************************************\n");
    }
}

Finally call setupSecurity in main() :

registerNodes();

whereas the placement of this statement can be in any order after the platformlayer has been initialized.

Step 2: Implementing unregisterNodes()

In order to delete shortcuts in the server created by registerNodes() add the following code to header,

/* OPC UA service calls */ 

. . .
 
void unregisterNodes();

and source file, rsp.:

/*============================================================================
   unregisterNodes - RegisterNodes for frequently use in read or write
 *===========================================================================*/
void unregisterNodes()
{
    printf("\n\n****************************************************************\n");
    printf("** Try to call unregisterNodes for removing node ids\n");
    if ( g_pUaSession == NULL )
    {
        printf("** Error: Server not connected\n");
        printf("****************************************************************\n");
        return;
    }

    OpcUa_UInt32      i;
    OpcUa_UInt32      count;
    UaStatus          status;
    UaNodeIdArray     nodesToUnregister;
    ServiceSettings   serviceSettings;

    // Initialize IN parameter nodesToRegister 
    count = g_VariableNodeIds.length();
    nodesToUnregister.create(count);
    for ( i=0; i<count; i++ )
    {
        g_VariableNodeIds[i].copyTo(&nodesToUnregister[i]);
    }

    /********************************************************************* 
     Call registerNodes service 
    **********************************************************************/
    status = g_pUaSession->unregisterNodes(
        serviceSettings,     // Use default settings
        nodesToUnregister);  // Array of nodeIds to unregister
    /*********************************************************************/
    if ( status.isBad() )
    {
        printf("** Error: UaSession::unregisterNodes failed [ret=%s] **\n", status.toString().toUtf8());
    }
    else
    {
        printf("** UaSession::unregisterNodes succeeded\n");
    }

    buildNodeIds();

    printf("****************************************************************\n");
}

Finally call unregisterNodes() in main() :

registerNodes();

. . . 

// ++
unregisterNodes();
// ++