สอบถามโปรแกรมอ่าน serial port หน่อยครับ พอใช้ไปนานๆ แล้วกดปิดมันค้างครับ

Imports System
Imports System.Threading
Imports System.IO.Ports
Imports System.ComponentModel
Imports System.IO


Public Class Form1


    '------------------------------------------------
    Dim myPort As Array
    Dim filePath As String

    Delegate Sub SetTextCallback(ByVal [text] As String) 'Added to prevent threading errors during receiveing of data
    '------------------------------------------------

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        SerialPort1.PortName = "COM1"
        SerialPort1.BaudRate = "9600"
        SerialPort1.Open()
        'myPort = IO.Ports.SerialPort.GetPortNames()
        'ComboBox1.Items.AddRange(myPort)
        
        Timer1.Enabled = True
        Timer1.Interval = 1000

        Dim Weight As String = RichTextBox2.Text.Length()
        
        TextBox1.Text = Weight
    End Sub


    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        SerialPort1.Write(RichTextBox2.Text & vbCr) 'concatenate with \n
        'SaveTextToFile(RichTextBox2.Text, "D:\weight.txt")
        filePath = System.IO.Path.Combine(
               My.Computer.FileSystem.SpecialDirectories.MyDocuments, "weight.txt")
        My.Computer.FileSystem.WriteAllText(filePath, RichTextBox2.Text, False)

        Dim Weight As String = RichTextBox2.Text.Length()
        If Weight > 400 Then
            RichTextBox2.Text = ""
        End If



    End Sub
    


    Private Sub SerialPort1_DataReceived(ByVal sender As System.Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
        ReceivedText(SerialPort1.ReadExisting())
    End Sub



    Private Sub ReceivedText(ByVal [text] As String) 'input from ReadExisting
        If Me.RichTextBox2.InvokeRequired Then
            Dim x As New SetTextCallback(AddressOf ReceivedText)
            Me.Invoke(x, New Object() {(text)})
        Else
            Me.RichTextBox2.Text &= [text] 'append text
        End If
    End Sub



    Public Function SaveTextToFile(ByVal strData As String, _
     ByVal FullPath As String, _
       Optional ByVal ErrInfo As String = "") As Boolean

        'Dim Contents As String
        Dim bAns As Boolean = False
        Dim objReader As StreamWriter
        Try
            objReader = New StreamWriter(FullPath)
            objReader.Write(strData)
            objReader.Close()
            bAns = True
        Catch Ex As Exception
            ErrInfo = Ex.Message

        End Try
        Return bAns
    End Function
     
   
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Timer1.Stop()
        Timer1.Enabled = False


        If SerialPort1.IsOpen Then
            SerialPort1.Close()
        End If

        Application.Exit()

    End Sub
End Class