VS2008下，串口操作问题求教

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        On Error Resume Next
        Timer1.Enabled = True
        Timer1.Interval = 1000
        SerialPort1.BaudRate = 9600 '波特率设为
        SerialPort1.PortName = "COM2" '端口为串口
        SerialPort1.ReceivedBytesThreshold = 1
        SerialPort1.Open() '打开串口

        SerialPort1.Write("gadgasgd")
    End Sub

为什么串口没有输出，而用WinCE自带的串口调试助手就可以发送出数据，