如何使用Softing工具包从OPC UA服务器的异步读取操作的回调中的DataValue响应中获取NodeId详细信息

Question

image shows the uint32 value but i need the NodeId details too, which is "Counter1" as in the NodeId in readAsync I am using Softing OPC UA toolkit to develop a client. With session->readAsync() i try to read value from OPC UA server, the callback method onReadComplete is invoked with the vector of DataValue requested for, i could get the value from the DataValue but unable to get the NodeId with namespaceIndex, indentifierType, identifier. In Visual Studio debugger these values are Unable to read memory.

read async:

std::vector<ReadValueId> readValueId1s;
ReadValueId ReadValueId1;
ReadValueId1.setNodeId(NodeId(2, _T("Counter1")));
ReadValueId1.setAttributeId(EnumAttributeId_Value);
readValueId1s.push_back(ReadValueId1);

// read the variable asynchronously
result = session->readAsync(pRdReq, EnumTimestampsToReturn_Both, 
readValueId1s, 0, pRdReq->getTransId());

callback method:

void TestSession::onReadComplete(void* requestHandle, EnumStatusCode 
serviceResult, std::vector<DataValue>& values)
{
    for (unsigned int i = 0; i < values.size(); i++) {
        std::wcout << values[i].getValue()->getNodeId().toString() << std::endl;
    }
}

Answer 1

Please take a look at the OPC UA Specification Part 4 - Services Chapter 5.10.2 Read

An OPC UA Read Response contains an array of DataValue. Each OPC UA DataValue structure contains

• StatusCode
• SourceTimestamp
• ServerTimestamp
• SourcePicoseconds
• ServerPicoseconds
• Value

An OPC UA Value structure contains

• ArrayType (0 in your case = Scalar)
• DataType (6 in your case = OpcUaType_Int32)
• Value (from an Union depending on the ArrayType and the DataType value)

So actually in your case the value is Int32 Variant Union value = 46132370

Edit

The order of the DataValue in the ReadResponse DataValue Array match with the order of Read NodeId from the ReadRequest you have sent. You should then save the information before sending the ReadRequest in order to know for which NodeId the DataValue ["X"] is the value.