Django will not listen to same port on IPv4 and IPv6 at the same time

[Erik Nordstroem]

By itself, python3 manage.py runserver 0.0.0.0:8000 works.

By itself, python3 manage.py runserver [::]:8000 works.

But if I try first python3 manage.py runserver 0.0.0.0:8000 and then python3 manage.py runserver[::]:8000, I am told, incorrectly, by the second process that:

Error: That port is already in use.

Same goes if I run python3 manage.py runserver [::]:8000 first followed by python3 manage.py runserver 0.0.0.0:8000; the first process runs but the second process will report:

Error: That port is already in use.

[Tim Graham]

What's your use case for development such that you need to listen to both protocols?

[Erik Nordstroem]

@timgraham: For consistency between dev and prod.

[Tim Graham]

I think integrating with a more fully featured web server is a better long term solution than trying to enhance the built-in webserver (#21978). This is consistent with the decision about ​whether or not to add SSL support to runserver.