const string sRequest =
    "\xa2\x48\x00\x00\x00\x01\x00\x00" +
    "\x00\x00\x00\x00\x20\x43\x4b\x41" +
    "\x41\x41\x41\x41\x41\x41\x41\x41" +
    "\x41\x41\x41\x41\x41\x41\x41\x41" +
    "\x41\x41\x41\x41\x41\x41\x41\x41" +
    "\x41\x41\x41\x41\x41\x00\x00\x21" +
    "\x00\x01";

    //10.20.202.134
    public static string nbtstat(string ipAddress, int timeout, out string netbiosname, out SocketError errorcode)
    {

        int port = 137;
        string Group = "";
        netbiosname = "";
        errorcode = SocketError.Success;

        byte[] receiveBytes = new byte[512];
        byte[] request = sRequest.Select(r => Convert.ToByte(r)).ToArray();

        using (Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp))
        {
            try
            {
                s.Connect(ipAddress, port);
                s.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, timeout);

                s.Send(request);
                s.Receive(receiveBytes);
            }
            catch (SocketException se)
            {

                errorcode = se.SocketErrorCode;
            }
            catch (Exception)
            {
                errorcode = SocketError.SocketError;
            }
        }

        if (errorcode == SocketError.Success)
        {
            int offset = 56;
            int replies = receiveBytes[offset++];
            for (int j = 0; j < replies; j++)
            {
                Byte[] field = receiveBytes.Skip(offset).Take(18).ToArray();
                string name = Encoding.ASCII.GetString(field.Take(15).ToArray());
                byte type = field[15];
                byte cl = field[16];
                offset += 18;
                if (type == 0x0)
                {
                    if ((cl == 0xC4 || cl == 0x84 || cl == 0xa4))
                    {
                        if (Group == "")
                        Group = name.TrimEnd();
                    }
                }
                if (type == 0x0 || type == 0x20)
                {
                    if (cl == 0x44 || cl == 0x4 || cl == 0x24)
                    {
                        if (netbiosname=="")
                        netbiosname = name.TrimEnd();
                    }
                }
            }
        }
        return Group;
    }