用户通过哪个ip和端口访问jupyterhub:通过c.JupyterHub.ip和c.JupyterHub.port来设置
当Proxy 或Spawners是远程服务时，通过哪个ip和端口来和hub通信：c.JupyterHub.hub_ip和c.JupyterHub.hub_port
当hub在容器里时，可以配置：
c.JupyterHub.hub_ip = '0.0.0.0' # listen on all interfaces
c.JupyterHub.hub_connect_ip = '10.0.1.4' # ip as seen on the docker network. Can also be a hostname.
