Public Class Form1
Dim WithEvents myComPort As New System.IO.Ports.SerialPort
Dim data As String
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
ComboBox1.Enabled = True
Button2.Enabled = False
Button1.Enabled = True
RadioButton1.Enabled = False
RadioButton2.Checked = True
myComPort.Close()
End Sub

Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
If Not ComboBox1.SelectedItem Is Nothing Then
If Not myComPort.IsOpen Then
Try
myComPort.BaudRate = 2400
myComPort.PortName = ComboBox1.SelectedItem
myComPort.Parity = IO.Ports.Parity.None
myComPort.DataBits = 8
myComPort.StopBits = IO.Ports.StopBits.One
myComPort.Handshake = IO.Ports.Handshake.None
myComPort.ReadTimeout = 3000
myComPort.ReceivedBytesThreshold = 1
myComPort.DtrEnable = True

myComPort.Open()

ComboBox1.Enabled = False
Button1.Enabled = False
Button2.Enabled = True
RadioButton1.Enabled = True
RadioButton1.Checked = True

Catch ex As Exception
MsgBox("Error Opening COM Port", MsgBoxStyle.Critical)
End Try
End If
Else
MsgBox("Select a valid COM Port", MsgBoxStyle.Information)
End If
End Sub

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
For Each portName As String In My.Computer.Ports.SerialPortNames
ComboBox1.Items.Add(portName)
Next
CheckBox1.Checked = True
If Not myComPort.IsOpen Then
Button2.Enabled = False
ComboBox1.Text = ComboBox1.Items(0)
RadioButton1.Enabled = False
RadioButton2.Checked = True
Else
Button1.Enabled = False
ComboBox1.Text = myComPort.PortName
RadioButton2.Checked = True
End If
End Sub

Private Sub RadioButton1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButton1.CheckedChanged
myComPort.DtrEnable = True
End Sub

Private Sub RadioButton2_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButton2.CheckedChanged
myComPort.DtrEnable = False
End Sub
Private Sub DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles myComPort.DataReceived
TextBox1.Invoke(New myDelegate(AddressOf updateTextBox), New Object() {})
End Sub
Public Delegate Sub myDelegate()
Public Sub updateTextBox()

data = data + myComPort.ReadExisting()
If Len(data) = 12 Then
TextBox1.Text = TextBox1.Text + Microsoft.VisualBasic.Mid(data, 2, 11) & vbLf
myComPort.DtrEnable = False
RadioButton1.Enabled = False
RadioButton2.Checked = True

If CheckBox1.Checked = True Then
Beep()
End If

Dim timeOut As DateTimeOffset = Now.AddMilliseconds(1500)
Do
Application.DoEvents()
Loop Until Now > timeOut
data = myComPort.ReadExisting()
myComPort.DiscardInBuffer()
data = ""
myComPort.DtrEnable = True
RadioButton1.Enabled = True
RadioButton1.Checked = True

End If
End Sub

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
TextBox1.Text = ""
End Sub
End Class