This was very frustrating I have to say! After coming to Punta del Diablo in Uruguay to have some time away from big cities like NYC. At the same time I wanted to do some self skills improvement while away. I started learning more about APIs, but I kept getting issues with postman not seeing my localhost. I was not aware upgrading from BigSur to Sonoma will also mess things up here.
After taking a long walk by the empty beach town in Punta del Diablo and coming back to my self learning adventure (learning Python REST APIs using Flask). I encounter another issue when I ran:
flask run
I got error:
Address already in use
Port 5000 is in use by another program. Either identify and stop that program, or start the server with a different port.
On macOS, try disabling the 'AirPlay Receiver' service from System Preferences -> General -> AirDrop & Handoff.
WTF! I said. But, wait…this error was useful. I did not know about this ‘AirPlay Receiver’ sh!t. So, I went to check those settings in my mac and turn it OFF:

Before doing the above I checked for open ports using my Terminal with the command lsoft -i :5000 I got:

After disabling ‘AirPlay Receiver’ Postman worked using:
localhost:5000
Why is Apple doing this? Why take port 5000 for these services? If you have any clues write them in the comments area below. Thanks.
You can always contact me if you have any questions or if you like collaborate.