Чтение данных через COM порт

Declare Function CreateFile Lib "kernel32" Alias "CreateFileA" (ByVal lpFileName As String, ByVal dwDesiredAccess As Long, ByVal dwShareMode As Long, ByVal lpSecurityAttributes As Long, n byte.
    BaudRate As Long        'Speed of data exchangeб, bps
    fBitFields As Long      'Bit field for setting of port
    wReserved As Integer    'Reserved
    XonLim As Integer       'minimum number of bytes in the buffer to send Xon
    XoffLim  = False Then
            MsgBox ("Error Setting port:" & GetLastError)
        End If
        MsgBox ("The port is opened")
       
    End If
    
End Function

Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long
 
'Function of closing the port
Function Com_Close() As Boolean
    Dim Retval As Long
    
    Retval = CloseHandle(Com_Handle)
    If Retval = 0 Then
        MsgBox ("Error while closing the port")
    Else
        MsgBox ("Port closed")
    End If
End Function

Declare Function WriteFile Lib "kernel32" (ByVal hFile As Long, lpBuffer As Any, ByVal nNumberOfBytesToWrite As Long, lpNumberOfBytesWritten As Long, ByVal lpOverlapped As Long) As Boolean
 
Declare Function GetLastError Lib "kernel32" () As Long
 
'Recording function to the port
Function Com_Write(n As Long)
    Dim Len_Buf As Long
    Dim Retval As Boolean
  
    Retval = WriteFile(Com_Handle, Buf(0), n, Len_Buf, 0)
    If Retval = False Then
        MsgBox ("Error Write port:" & GetLastError)
    End If
   
End Function

'Write port
Sub Command4_Click()
    Dim s As String
    Dim n As Long
    Dim a As Integer
    Dim Retval As Long
    
    s = Text2.Text
    n = Len(s)
    For a = 1 To n
        Buf(a - 1) = Asc(Mid(s, a, 1))
    Next a
    Com_Write (n)
End Sub

Declare Function ReadFile Lib "kernel32" (ByVal hFile As Long, lpBuffer As Any, ByVal nNumberOfBytesToRead As Long, lpNumberOfBytesRead As Long, lpOverlapped As Long) As Boolean
 
Declare Function GetLastError Lib "kernel32" () As Long
 
Global Com_Handle As Long 'Descriptor of port
Global Buf(1024) As Byte 'The buffer of port
Global Com_Byte_Read As Long 'количество принятых байт
 
 
'function of reading from the port
Function Com_Read()
    Dim Retval As Boolean
    
    Retval = ReadFile(Com_Handle, Buf(0), 1024, Com_Byte_Read, 0)
    If Retval = False Then
        MsgBox ("Error Read port:" & GetLastError)
    End If
  
End Function

'Read port
Private Sub Command3_Click()
   Dim s As String
    Dim a As Long
    
   Com_Read
   For a = 1 To Com_Byte_Read
        s = s & Chr(Buf(a - 1))
   Next a
   Text1.Text = s
End Sub