Sub CloseComPort()

Using myComPort

If (Not (myComPort Is Nothing)) Then

' The COM port exists.

If myComPort.IsOpen Then

' Wait for the transmit buffer to empty.

Do While (myComPort.BytesToWrite > 0)
Loop

End If
End If

End Using

End Sub

Listing 3. The End Using statement closes the port and disposes of its resources.