how to bypass the port 9000 barrier [zeppelin with nginx]

[Scarlet Frank]

Hi !
I recently tried to set up zeppelin with nginx. My initial plan was like 
"zeppelin serves on port 8080 and nginx listens on port 9000"
It immediately comes up with a problem that both websocket and API requests are 
sent to port 8080. The problem disappears when I change the nginx listen port 
from 9000 to 9001.
In Zeppelin 
Configuration<https://zeppelin.apache.org/docs/0.10.0/setup/operation/configuration.html>
 page, it says that zeppelin server port should not be the same with zeppelin 
web application development port.
My Aim:

1.      visit production:9000/zeppelin/ to access zepnode:8080 (zeppelin 
server). Port is constrained in production environment.
Questions:

1.      Does this rule also apply to nginx reverse proxy ? (port != 9000).

2.      Is it hard-coded in zeppelin-web project (9000 port for web application 
development) or I could change a config in the project and build a custom war 
myself?
My configurations are list below:

-       zeppelin/conf/zeppelin-site.xml
<property>
  <name>zeppelin.server.port</name>
  <value>8067</value>
  <description>Server port.</description>
</property>

-       nginx/site-available/zeppelin.conf
upstream zeppelin {
        server 127.0.0.1:8067;
}
# Zeppelin Website
server {
              # 9000 before
        listen 9001;
        location / {
                proxy_pass http://zeppelin;
                proxy_set_header X-Real-IP $remote_addr;
                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_set_header Host $http_host;
                proxy_set_header X-NginX-Proxy true;
                proxy_redirect off;
                #auth_basic "Restricted";
                #auth_basic_user_file /etc/nginx/.htpasswd;
        }
        location /ws {
                proxy_pass http://zeppelin/ws;
                proxy_http_version 1.1;
                proxy_set_header Upgrade websocket;
                proxy_set_header Connection upgrade;
                proxy_read_timeout 86400;
        }
}
Did anyone encounter a similar issue?
I can provide more details if needed. :D
Some references:
Apache Zeppelin 0.10.0 Documentation: HTTP Basic Auth using 
NGINX<https://zeppelin.apache.org/docs/0.10.0/setup/security/authentication_nginx.html>
Thanks,
Scarlet