SerialPort Problem in A hardware interface

Public Class Form1
    Dim msg As String

    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        With SerialPort1
            If .IsOpen = True Then .Close()
        End With
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    End Sub
    Private Sub search()
        Dim s As String = ""
        Dim ma As Byte = My.Computer.Ports.SerialPortNames.Count - 1
        ComboBox1.Items.Clear()
        For i As Byte = 0 To ma
            s = My.Computer.Ports.SerialPortNames(i).ToString
            If InStr(s, "i") = 0 Then
                ComboBox1.Items.Add(s)
            End If
        Next
        ma = ComboBox1.Items.Count
        If ma > 0 Then
            ComboBox1.SelectedIndex = ma - 1
        End If
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        search()
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        If ComboBox1.Text <> "" Or InStr(ComboBox1.Text, "m") = 0 Then
            With SerialPort1
                Try
                    If .IsOpen = True Then .Close()
                Catch ex As Exception
                    MsgBox("Error 1", MsgBoxStyle.Information, "Error")
                    Exit Sub
                End Try
                .DataBits = 8
                .BaudRate = 4800
                .StopBits = IO.Ports.StopBits.One
                .Parity = IO.Ports.Parity.None
                .Handshake = IO.Ports.Handshake.None
                .PortName = ComboBox1.Text
                AddHandler SerialPort1.DataReceived, AddressOf SerialPort1_DataReceived
                Try

                    .Open()
                Catch ex As Exception
                    MsgBox(Err.Description, MsgBoxStyle.Information, "Error")
                    Me.Show()
                    Exit Sub
                End Try
                MsgBox("Connected")
            End With
        End If
    End Sub
    Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
        Try
            msg = msg & SerialPort1.ReadExisting

            Me.Invoke(New EventHandler(AddressOf baby))
        Catch ex As Exception

        End Try
    End Sub
    Private Sub baby()
        If InStr(msg, "OK") > 0 Then
            ListBox1.Items.Add(msg)
            msg = ""
        End If
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        With SerialPort1
            Try
                If .IsOpen = True Then .Close()
            Catch ex As Exception
                MsgBox("Error 2", MsgBoxStyle.Information, "Error")
                Exit Sub
            End Try
        End With
    End Sub
End Class