Public Class Form1
    Dim WithEvents serialPort As New IO.Ports.SerialPort

    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
        Dim rcvBuf(1024) As Byte
        serialPort.Read(rcvBuf, 0, rcvBuf.Length)
        'txtDataReceived.Invoke(New myDelegate(AddressOf updateTextBox), New Object() {})
    End Sub

    Private Sub btnSend_Click( _
       ByVal sender As System.Object, _
       ByVal e As System.EventArgs) _
       Handles btnSend.Click
        Try
            Dim xmtBuf() As Byte = {&H96, &H1, &H50, &H51, &H74}
            serialPort.Write(xmtBuf, 0, xmtBuf.Length)
            With txtDataReceived
                .SelectionColor = Color.Black
                .AppendText(txtDataToSend.Text & vbCrLf)
                .ScrollToCaret()
            End With
            txtDataToSend.Text = String.Empty
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try

    End Sub

    Public Delegate Sub myDelegate()
    Public Sub updateTextBox()
        With txtDataReceived
            .Font = New Font("Garamond", 12.0!, FontStyle.Bold)
            .SelectionColor = Color.Red
            .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()

            lblMessage.Text = cbbCOMPorts.Text & " connected."
            btnConnect.Enabled = False
            btnDisconnect.Enabled = True
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
    End Sub
End Class