尝试通过Serialport向Verifone发送金额

Question

帮助我，我正在尝试从PCc汇款到Veriphone签证。万事达卡，但出现错误

        SerialPort1.Open()
        Dim MyInt As Integer = Val(TextBox1.Text)
        Dim b As Byte() = BitConverter.GetBytes(MyInt)
        SerialPort1.Write(b, 0, b.Length)
        SerialPort1.Close()

错误：