Can't set the application port to run LoRaWAN certification tests

Port 1 to 223 are used for the application. The port is one byte int the LoRaWAN Protocol. Setting port to 224 is illegal from an application perspective, it is the port for testing.

Have you tried using setTestModeEnabled(true) command. I'm assuming it will set the port to 224 or it may allow you to set the port afterwards.

Also note: Ports 225 - 255 are reserved for the future

See the Specification for further info

The purpose of the FPort value 224 is to provide a dedicated FPort to run MAC compliance test scenarios over-the-air on final versions of end-devices, without having to rely on specific test versions of end-devices for practical aspects. The test is not supposed to be simultaneous with live operations, but the MAC layer implementation of an end-device SHALL be exactly the one used for the normal application. The test protocol is encrypted using the AppSKey. This ensures that the Network cannot enable the end-device’s test mode without involving the end-device’s owner.