Why does eventlet/socketio not work when the server is run from a function?

The code below works as expected and runs without problem:

import socketio
import eventlet

port = 5000
sio = socketio.Server()
app = socketio.WSGIApp(sio, static_files={})

@sio.event
def connect(sid, environ):
    print('Connect')

eventlet.wsgi.server(eventlet.listen(('', port)), app) # Note this line

However, as soon as the final line is wrapped in a function, an error occurs

import socketio
import eventlet

port = 5000
sio = socketio.Server()
app = socketio.WSGIApp(sio, static_files={})

@sio.event
def connect(sid, environ):
    print('Connect')

def run():
    eventlet.wsgi.server(eventlet.listen('', port), app) # Note this line

run()

This is the full error message:

Traceback (most recent call last):
  File "/home/thatcoolcoder/coding/micro-chat/tester3.py", line 16, in <module>
    run()
  File "/home/thatcoolcoder/coding/micro-chat/tester3.py", line 14, in run
    eventlet.wsgi.server(eventlet.listen('', port), app)
  File "/usr/lib/python3.9/site-packages/eventlet/convenience.py", line 49, in listen
    sock = socket.socket(family, socket.SOCK_STREAM)
  File "/usr/lib/python3.9/site-packages/eventlet/greenio/base.py", line 136, in __init__
    fd = _original_socket(family, *args, **kwargs)
  File "/usr/lib/python3.9/socket.py", line 232, in __init__
    _socket.socket.__init__(self, family, type, proto, fileno)
OSError: [Errno 97] Address family not supported by protocol

How can I prevent this? I'm building a small chat app and to keep things clean, I need to create and run the server from within a function (specifically a class method).

from Why does eventlet/socketio not work when the server is run from a function?