Robert 的部落格

public static bool IsConnectingServer()
{
    string serverAddress = Properties.Settings.Default.ServerAddress;
    try
    {
        HttpWebRequest request = (HttpWebRequest) WebRequest.Create( serverAddress );
        request.Method = "HEAD";
        HttpWebResponse response = (HttpWebResponse) request.GetResponse();
        return response.StatusCode == HttpStatusCode.OK;
    } catch ( Exception )
    {
        return false;
    }
}

來源：C# Check Remote Server

參考：
Check whether a server is online using an IP and Port
Checking whether the server is on/off