I am performing a functional test after installation according to the MCU installation guide. In the jsvascript example, port 8081 fails to access the rest method. So when I look at the listening port on the server, it listens to 3000, 3001, 3004, 8080, and so on. But the 8081 is invisible. In portal / portal.toml, rest_port is set to 8081. What do I need to check to get the 8081 up and running?