add these lines to nginx config

gistfile1.txt

upstream railsapp {
  server 0.0.0.0:5000 weight=10 max_fails=5 fail_timeout=30s;
}

server {
  listen 80;
  server_name admin.com;

  location / {
    proxy_pass http://railsapp/;
    proxy_set_header X-Real-IP  $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  }
}

you need to kill the process listening on port 80.