COM - CoCreateInstanceEx always creates a new Object - c++

Question

I am using the COM CoCreateInstanceEx API to create an instance of a specific class on a local computer.
I am using the same function again to get the instance which was created earlier but it creates a new instance.
Is it the right way to get the object of the class from running instance or should I use any other method ?
C++ Code snippet:
HRESULT nResult = CLSIDFromProgID(OLESTR("ABC"), &clsid);
MULTI_QI mqi[1];
mqi[0].pIID = &IID_IUnknown;
mqi[0].pItf = NULL;
mqi[0].hr = 0;
nResult = CoCreateInstanceEx(clsid, NULL, CLSCTX_LOCAL_SERVER, NULL, 1, mqi);
IUnknown *pUnk = mqi[0].pItf;

Answer 1

Is it the right way to get the object of the class from running instance or should I use any other method ?
No it is not. CoCreateInstanceEx delves into the depths of the COM factory mechanics to get the factory for the object required and creates a new one.
To get a "copy" of the same instance you last used, there are some options to choose from;
Call AddRef() on the first created object to increment the COM objects reference count for the copy of the object pointer you are about to make. You then use that pointer until it is no longer required, then call Release(). The Release() decrements the reference count and, if it is the last reference, the COM object can destroy itself. This does not perform a deep copy of the object and its contents.
If you have access to the code, you make the COM object a singleton or otherwise modify the lifetime as you require it. If the COM object code uses the ATL, there a several macros here that can assist, in particular DECLARE_CLASSFACTORY_SINGLETON.
Create a Clone() method on the COM object that performs the deep copy, the exact mechanism here would depend on the object itself, but typically it is nothing more than the usual coping the appropriate data fields.
Frankly though, unless this is an exercise in learning how COM works, don't use naked pointers and try to manage the objects lifetime manually. Use the ATL classes, in particular ATL::CComPtr<> and it takes care of these issues as you would expect it to.
You don't specify in too much detail how and where the object is created. There are more advanced object registration and retrieval techniques that allow a greater level of control over the objects creation, lifetime and use. You could explore these if they are suitable;
The active object mechanisms of GetActiveObject et al.
If the object being used registers itself with the ROT (the running object table), you could also explore the using the ROT.