Event sent by Windows when connected to internet - c++

Question

I need to know in my program when the connection to internet is back.
Actually I can check if it is connected with something like
CComPtr<INetworkListManager> pNLM;
HRESULT hr = CoCreateInstance(CLSID_NetworkListManager, NULL, CLSCTX_ALL, __uuidof(INetworkListManager), (LPVOID*)&pNLM);
if (SUCCEEDED(hr))
{
VARIANT_BOOL isConnected;
pNLM->get_IsConnectedToInternet(&isConnected);
if (isConnected == VARIANT_TRUE)
But I cannot find a nice way to get informed that the connection is back.
Polling is not a nice way, to me.
I've found ::NotifyAddrChange() but this is triggered whenever change occurs in the table that maps IPv4 addresses to interfaces.
Is there a specific event that is sent when the connection is established?

Answer 1

Thanks to a colleague of mine, I have the answer.
This is the class that will call the callback
#include "Event.h"
Event::Event(const std::function<void()>& cb)
: methodTobeCalled(cb)
{
}
HRESULT Event::NetworkConnectionConnectivityChanged(GUID, NLM_CONNECTIVITY)
{
if (methodTobeCalled)
methodTobeCalled();
return S_OK;
}
HRESULT Event::NetworkConnectionPropertyChanged(GUID, NLM_CONNECTION_PROPERTY_CHANGE)
{
return S_OK;
}
STDMETHODIMP Event::QueryInterface(REFIID refIID, void** pIFace)
{
HRESULT hr = S_OK;
*pIFace = nullptr;
if (IsEqualIID(refIID, IID_IUnknown))
{
*pIFace = (IUnknown *)this;
((IUnknown *)*pIFace)->AddRef();
}
else if (IsEqualIID(refIID, IID_INetworkConnectionEvents))
{
*pIFace = (INetworkConnectionEvents *)this;
((IUnknown *)*pIFace)->AddRef();
}
else
{
hr = E_NOINTERFACE;
}
return hr;
}
ULONG Event::AddRef(void)
{
return static_cast<ULONG>(InterlockedIncrement(&m_ref));
}
ULONG Event::Release(void)
{
LONG Result = InterlockedDecrement(&m_ref);
return static_cast<ULONG>(Result);
}
In the ctor of the main class (no error handling here):
::CoInitializeEx(nullptr, COINIT_APARTMENTTHREADED);
::CoCreateInstance(CLSID_NetworkListManager, nullptr, CLSCTX_ALL, IID_INetworkListManager, (LPVOID *)&m_pNLM);
m_pNLM->QueryInterface(IID_IConnectionPointContainer, (void **)&m_pCpc);
m_pCpc->FindConnectionPoint(IID_INetworkConnectionEvents, &m_pConnectionPoint);
m_event = std::make_unique<NetworkEvent>(std::bind(&MainClass::methodTobeCalled, this));
hr = m_pConnectionPoint->Advise((IUnknown *)m_event.get(), &m_cookie);
The variables needed:
std::unique_ptr<NetworkEvent> m_event;
DWORD m_cookie;
CComPtr<IConnectionPoint> m_pConnectionPoint;
CComPtr<INetworkListManager> m_pNLM;
CComPtr<IConnectionPointContainer> m_pCpc;
The method that will be called at each network event, will be
MainClass::methodTobeCalled()
In this method one can then check if the connection is available or not.
O can check the NLM_CONNECTIVITY flags in NetworkConnectionConnectivityChanged()