failed to run jupyterhub when changing default port - jupyter

Question

I'm trying to set up jupyterhub. The 8000 is used for a different program, so I have to use a different port.
I change the file /etc/jupyterhub/jupyterhub_config.py add/uncomments:
c.JupyterHub.hub_port = 9003
c.JupyterHub.ip = '111.111.11.1'
c.JupyterHub.port = 9002
c.ConfigurableHTTPProxy.api_url = 'http://127.0.0.1:9000'
when I tried to running jupyterhub, I got the error:
[W 2020-06-03 14:48:48.930 JupyterHub proxy:554] Stopped proxy at pid=47639
[W 2020-06-03 14:48:48.932 JupyterHub proxy:643] Running JupyterHub without SSL. I hope there is SSL termination happening somewhere else...
[I 2020-06-03 14:48:48.932 JupyterHub proxy:646] Starting proxy # http://111.111.11.1:9002/
14:48:49.301 [ConfigProxy] info: Proxying http://111.111.11.1:9002 to (no default)
14:48:49.307 [ConfigProxy] info: Proxy API at http://127.0.0.1:9000/api/routes
14:48:49.315 [ConfigProxy] error: Uncaught Exception
[E 2020-06-03 14:48:49.437 JupyterHub app:2718]
Traceback (most recent call last):
File "/home/user/miniconda/2020.02/python/3.7/lib/python3.7/site-packages/jupyterhub/app.py", line 2716, in launch_instance_async
await self.start()
File "/home/user/miniconda/2020.02/python/3.7/lib/python3.7/site-packages/jupyterhub/app.py", line 2524, in start
await self.proxy.get_all_routes()
File "/home/user/miniconda/2020.02/python/3.7/lib/python3.7/site-pack#c.JupyterHub.hub_ip = '127.0.0.1'
ages/jupyterhub/proxy.py", line 806, in get_all_routes
resp = await self.api_request('', client=client)
File "/home/user/miniconda/2020.02/python/3.7/lib/python3.7/site-packages/jupyterhub/proxy.py", line 774, in api_request
result = await client.fetch(req)
tornado.httpclient.HTTPClientError: HTTP 403: Forbidden
What is the correct way to install jupyterhub on a port other than 8000?
Thanks.

Answer 1

I think some of these parameters are now obsolete, so it may depend which version you are running, but I'll assume JupyterHub 1.0+.
There are a few different services that make up JupyterHub, and the 'hub' service, confusingly, as not actually the one you are concerned with. The proxy is the main entrypoint to the application, and it proxies traffic to the hub by default, and to specific user Jupyter servers if the traffic is to a /user/ URL.
In addition, the 'hub' service also has an API endpoint that user servers can access directly (this doesn't go through the proxy). And the proxy has an extra API endpoint too, for direct access from the hub...
It is the proxy service that defaults to port 8000. To change to 80, for example try this:
## The public facing URL of the whole JupyterHub application.
#
# This is the address on which the proxy will bind. Sets protocol, ip, base_url
c.JupyterHub.bind_url = 'https://0.0.0.0:80'