port = new SerialPort("COM7", 250000, Parity.None, 8, StopBits.One);
            port.Handshake = Handshake.None;
            port.Open();

            byte[] a = new byte[4] { 50, 51, 52, 53 };
            byte[] c = new byte[4];

            port.Write(a, 0, 4);

            port.Read(c, 0, 4);

            for (int i = 0; i < 4; i++)
            {
                Console.WriteLine(c[i]);
            }

            Console.WriteLine("ok");