Public Class Form1

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

        For i As Integer = 0 To _
           My.Computer.Ports.SerialPortNames.Count - 1
            cbbCOMPorts.Items.Add( _
               My.Computer.Ports.SerialPortNames(i))
        Next
        btnDisconnect.Enabled = False
    End Sub

    Private Sub DataReceived( _
       ByVal sender As Object, _
       ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) _
       Handles serialPort.DataReceived

        txtDataReceived.Invoke(New _
                       myDelegate(AddressOf updateTextBox), _
                       New Object() {})
    End Sub

    Public Delegate Sub myDelegate()
    Public Sub updateTextBox()
        With txtDataReceived
            .Font = New Font("Garamond", 12.0!, FontStyle.Bold)
            .AppendText(serialPort.ReadExisting)
            .ScrollToCaret()
        End With
    End Sub

    Private Sub btnConnect_Click( _
       ByVal sender As System.Object, _
       ByVal e As System.EventArgs) _
       Handles btnConnect.Click
        If serialPort.IsOpen Then
            serialPort.Close()
        End If
        Try
            With serialPort
                .PortName = cbbCOMPorts.Text
                '.BaudRate = 96000
                '.Parity = IO.Ports.Parity.None
                '.DataBits = 8
                '.StopBits = IO.Ports.StopBits.One
                ' .Encoding = System.Text.Encoding.Unicode
            End With
            serialPort.Open()

            ToolStripStatusLabel1.Text = cbbCOMPorts.Text & " connected."

            btnConnect.Enabled = False
            btnDisconnect.Enabled = True
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
    End Sub

    Private Sub btnDisconnect_Click( _
       ByVal sender As System.Object, _
       ByVal e As System.EventArgs) _
       Handles btnDisconnect.Click
        Try
            serialPort.Close()
            ToolStripStatusLabel1.Text = serialPort.PortName & " disconnected."
            btnConnect.Enabled = True
            btnDisconnect.Enabled = False
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
    End Sub
End Class