I have been using the Open API successfully for several months. Recently, authorization attempts are failing. Please see the curl trace below for a typical example. When this request is executed, the Nanoleaf panel controller is in authorization mode (press & hold power button until light starts to flash). This occurs with 3.0.5 and 3.06 firmware, even after reseting the controller.
Yup that's the error you should be getting without the aurora being in authentication mode. Once you hold down the power button for 7 seconds and run the command again you should get a code 200.
port 6517 is for homekit. This is listed in bonjour as well under the _hap._tcp folder.
Unless you are a HK Client, you will not be able to connect to it easily.