When I connect my Arduino to my laptop and want to get serial data on my system, I get an exception about port access being denied. I am sure about the port number (COM4) and opening and closing ports. sometimes I reconnect the device it works.
>Solution :
Try these out:
-
if your Serial monitor on Arduino is not opened, be sure to close it.
-
check the port in system management of your system to be sure about
the port number again. -
be sure about closing your application each time you want to test,
because running an application will reserve the port and will not let
other apps use it.