Checking for internet connectivity

This is a technique I’ve used in the past to check for internet connectivity and it has never really failed to work for me. But I won’t say it’s a 100% safe method and you’ll have to verify that this works for your target environment before putting it into use.

BOOL CheckInternetConnection(LPCTSTR szURL)
{
    DWORD flags = 0;
    if( InternetGetConnectedState( &flags, 0 ) )
    {
        if( InternetCheckConnection( szURL,
            FLAG_ICC_FORCE_CONNECTION, 0 ) )
            return TRUE;
        else
            return FALSE;
    }
    else
        return FALSE;
}

And you can put the function to use as follows :-

if( CheckInternetConnection( "http://www.google.com" )
   || CheckInternetConnection( "http://www.microsoft.com" )
   || CheckInternetConnection( "http://www.yahoo.com" ) )
{
    // We are online
}
else
{
    // We are offline
}

You can replace the three web-sites I’ve used with your custom URLs if you want to do so, I just chose those three as I think the chances that all 3 of them are down at the same time are quite low.