One problem I have been working on is how to check if the host pc has an internet connection available.The answer is surprisingly easy, the solution is to use P/Invoke to call InternetGetConnectedState, which is a Windows API function that returns a Boolean to indicate if the host machine has an active internet connection.
This function takes two arguments :
The first is a pointer to a variable that receives the connection description. This parameter may return a valid flag even when the function returns FALSE. This parameter can be one or more of the following values.
| Value | Meaning |
INTERNET_CONNECTION_CONFIGURED
(0x40) | Local system has a valid connection to the Internet, but it might or might not be currently connected. |
INTERNET_CONNECTION_LAN
(0x02) | Local system uses a local area network to connect to the Internet. |
INTERNET_CONNECTION_MODEM
(0x01) | Local system uses a modem to connect to the Internet. |
INTERNET_CONNECTION_MODEM_BUSY
(0x08) | No longer used. |
INTERNET_CONNECTION_OFFLINE
(0x20) | Local system is in offline mode. |
INTERNET_CONNECTION_PROXY
(0x04) | Local system uses a proxy server to connect to the Internet. |
INTERNET_RAS_INSTALLED
(0x10) | Local system has RAS installed. |
The second one is a reserved variable that must be set to 0.
First Import the external DLL into your application
[DllImport("wininet.dll")]
private extern static bool InternetGetConnectedState(ref InternetConnectionState_e lpdwFlags, int dwReserved);
then add an enumeration to define the connection state (use of a modem, use of a proxy, offline mode..)
[Flags]
enum InternetConnectionState_e : int
{
INTERNET_CONNECTION_MODEM = 0x1,
INTERNET_CONNECTION_LAN = 0x2,
INTERNET_CONNECTION_PROXY = 0x4,
INTERNET_RAS_INSTALLED = 0x10,
INTERNET_CONNECTION_OFFLINE = 0x20,
INTERNET_CONNECTION_CONFIGURED = 0x40
}
It is then a fairly easy matter of calling the method to get the current connectivity state of the host.
public Boolean IsConnectedToInternet( )
{
Boolean isConnected;
InternetConnectionState_e flags = 0;
isConnected = InternetGetConnectedState(ref flags, 0);
return isConnected;
}