Private Sub conectar_Click()
'comprueva que el puerto este cerrado para poder abrirlo
If MSComm1.PortOpen = False Then
'determina el puerto que hemos seleccionado.
If COM_sel.ListIndex = 0 Then
MSComm1.CommPort = 1
End If
If COM_sel.ListIndex = 1 Then
MSComm1.CommPort = 2
End If
If COM_sel.ListIndex = 2 Then
MSComm1.CommPort = 3
End If
If COM_sel.ListIndex = 3 Then
MSComm1.CommPort = 4
End If
If COM_sel.ListIndex = 4 Then
MSComm1.CommPort = 5
End If
If COM_sel.ListIndex = 5 Then
MSComm1.CommPort = 6
End If
If COM_sel.ListIndex = 6 Then
MSComm1.CommPort = 7
End If
If COM_sel.ListIndex = 7 Then
MSComm1.CommPort = 8
End If
If COM_sel.ListIndex = 8 Then
MSComm1.CommPort = 9
End If
If COM_sel.ListIndex = 9 Then
MSComm1.CommPort = 10
End If
If COM_sel.ListIndex = 10 Then
MSComm1.CommPort = 11
End If
End If

MSComm1.OutBufferSize = 1 'tamaño del dato a transmitir.
MSComm1.InBufferSize = 23
MSComm1.InputMode = comInputModeText 'los datos se recuperan en modo texto.
MSComm1.InputLen = 23 ' BUFFER DE ENTRADA SE PUEDE DEJAR AL MAXIMO.
MSComm1.PortOpen = True
MSComm1.RThreshold = 23 'son 23 caracteres.
End Sub

Private Sub Form_Load()
COM_sel.AddItem "COM1"
COM_sel.AddItem "COM2"
COM_sel.AddItem "COM3"
COM_sel.AddItem "COM4"
COM_sel.AddItem "COM5"
COM_sel.AddItem "COM6"
COM_sel.AddItem "COM7"
COM_sel.AddItem "COM8"
COM_sel.AddItem "COM9"
COM_sel.AddItem "COM10"
COM_sel.AddItem "COM11"
COM_Sel.ListIndex = 0
End Sub

Private Sub MSComm1_OnComm()
Dim InBuff As String
Select Case MSComm1.CommEvent
Case comEvReceive
InBuff = MSComm1.Input
Debug.Print InBuff
Texto.Text = ""
Texto.Text = Left$(InBuff, 23) ' se recorta los caracteres basura
MSComm1.PortOpen = False 'cierra el puerto y vacia el buffer
End Select
End Sub