Permission error on port 80

@tiangolo any ideas on what could be causing this error:

papi_1       |   File "main.py", line 8, in <module>
papi_1       |     app.run(host='0.0.0.0', debug=True, port=80)
papi_1       |   File "/usr/local/lib/python3.6/site-packages/flask/app.py", line 841, in run
papi_1       |     run_simple(host, port, self, **options)
papi_1       |   File "/usr/local/lib/python3.6/site-packages/werkzeug/serving.py", line 795, in run_simple
papi_1       |     s.bind(get_sockaddr(hostname, port, address_family))
papi_1       | PermissionError: [Errno 13] Permission denied

Flask should always be listening on the port 80, right?

[tiangolo]

Read the Docker getting started guide: https://docs.docker.com/get-started/part2/#define-a-container-with-dockerfile

It should help clarify several things.

If you listen on port 80 inside the container doesn’t mean that it will be listening on port 80 outside. For it to listen outside you have to map the ports with something like "5555:80", that would make your host listen on port 5555 and send the communication to the port 80 inside the container.

[tiangolo]

Are you changing the name of the user by any chance?

For debugging purposes, try using a “non-privileged” port, like 8080, and see if that works. That would hint that there are issues with onwership of the file, root access, etc.