InternetCheckConnection always return false - windows

Question

I want to use the Wininet function InternetCheckConnection to check whenever the machine is connected to the internet and can access a specific host.
The problem is that this function is always returning false, no matter the URL I put on it.
MSDN link

Answer 1

Following combination works for me on Windows 7 and Windows XP SP3:
InternetCheckConnection("http://www.google.com", FLAG_ICC_FORCE_CONNECTION, 0) ;
GetLastError() returns 0 if the connexion is possible and it returns
12029 (The attempt to connect to the server failed) if not.
Following combonations don't work for me :
InternetCheckConnection(NULL, FLAG_ICC_FORCE_CONNECTION, 0) ;
GetLastError() returns 12016 (The requested operation is invalid).
InternetCheckConnection(NULL, 0, 0) ;
InternetCheckConnection(("http://www.google.com", 0, 0) ;
for both GetLastError() returns 2250 (The network connection could not be found).

Answer 2

Have you checked GetLastError() ? If I read MSDN correctly, you would need to check for ERROR_NOT_CONNECTED to determine whether you're truly offline.

Answer 3

Just a wild guess, but perhaps this is due to a personal firewall blocking all outgoing connections for one of the Windows DLLs and / or your application?

Answer 4

According to Microsoft API document InternetCheckConnection is deprecated.
[InternetCheckConnection is available for use in the operating systems specified in the Requirements section. It may be altered or unavailable in subsequent versions. Instead, use NetworkInformation.GetInternetConnectionProfile or the NLM Interfaces. ]
Instead of this API we can use INetworkListManager interface to check whether Internet is connected or not for windows platform.
Here below is the win32 codebase :
#include <iostream>
#include <ObjBase.h> // include the base COM header
#include <Netlistmgr.h>
// Instruct linker to link to the required COM libraries
#pragma comment(lib, "ole32.lib")
using namespace std;
enum class INTERNET_STATUS
{
CONNECTED,
DISCONNECTED,
CONNECTED_TO_LOCAL,
CONNECTION_ERROR
};
INTERNET_STATUS IsConnectedToInternet();
int main()
{
INTERNET_STATUS connectedStatus = INTERNET_STATUS::CONNECTION_ERROR;
connectedStatus = IsConnectedToInternet();
switch (connectedStatus)
{
case INTERNET_STATUS::CONNECTED:
cout << "Connected to the internet" << endl;
break;
case INTERNET_STATUS::DISCONNECTED:
cout << "Internet is not available" << endl;
break;
case INTERNET_STATUS::CONNECTED_TO_LOCAL:
cout << "Connected to the local network." << endl;
break;
case INTERNET_STATUS::CONNECTION_ERROR:
default:
cout << "Unknown error has been occurred." << endl;
break;
}
}
INTERNET_STATUS IsConnectedToInternet()
{
INTERNET_STATUS connectedStatus = INTERNET_STATUS::CONNECTION_ERROR;
HRESULT hr = S_FALSE;
try
{
hr = CoInitialize(NULL);
if (SUCCEEDED(hr))
{
INetworkListManager* pNetworkListManager;
hr = CoCreateInstance(CLSID_NetworkListManager, NULL, CLSCTX_ALL, __uuidof(INetworkListManager), (LPVOID*)&pNetworkListManager);
if (SUCCEEDED(hr))
{
NLM_CONNECTIVITY nlmConnectivity = NLM_CONNECTIVITY::NLM_CONNECTIVITY_DISCONNECTED;
VARIANT_BOOL isConnected = VARIANT_FALSE;
hr = pNetworkListManager->get_IsConnectedToInternet(&isConnected);
if (SUCCEEDED(hr))
{
if (isConnected == VARIANT_TRUE)
connectedStatus = INTERNET_STATUS::CONNECTED;
else
connectedStatus = INTERNET_STATUS::DISCONNECTED;
}
if (isConnected == VARIANT_FALSE && SUCCEEDED(pNetworkListManager->GetConnectivity(&nlmConnectivity)))
{
if (nlmConnectivity & (NLM_CONNECTIVITY_IPV4_LOCALNETWORK | NLM_CONNECTIVITY_IPV4_SUBNET | NLM_CONNECTIVITY_IPV6_LOCALNETWORK | NLM_CONNECTIVITY_IPV6_SUBNET))
{
connectedStatus = INTERNET_STATUS::CONNECTED_TO_LOCAL;
}
}
pNetworkListManager->Release();
}
}
CoUninitialize();
}
catch (...)
{
connectedStatus = INTERNET_STATUS::CONNECTION_ERROR;
}
return connectedStatus;
}