It's my understanding that being able to set a custom port instead of the one that's assigned by default is in the works, or already completed, as well as the inaccurate speed test results. I constantly wrestle with the combination of both of these elements and sometimes can't serve between build cycles because of the stars not aligning with these two elements.

That being said, I think it would make sense to check that the serving port is functional before even initiating a speed test -- if configured port fails when trying to switch serving mode on, inform the the user and do not proceed to the speed test step. I think it's better to get this out of the way first before going through a speed test and then trying to officially turn MASQ on in serving mode only to see this fail after you got through the speed test.