/// <summary>
/// Check internet connection.
/// </summary>
/// <returns>Connection state.</returns>
internal static bool IsNetAvail()
{
    try
    {
        var buffer = new byte[32];
        return new Ping().Send(link_base, TIME_OUT, buffer, new PingOptions()).Status == Success;
    }
    catch (Exception)
    {
        return false;
    }
}