nginx proxy to any port; i.e. requesting `http://ec2-xx-xx-xx-xx.compute.amazonaws.com/9001/` will forward to `localhost:9001`

nginx_port_proxy

  server {
    listen       80;
    server_name  localhost;
    location ~ /(\d+) {
      resolver 8.8.8.8;
      rewrite  ^/(\d+)/(.*) /$2 break;
      proxy_pass_header Server;
      proxy_set_header Host $http_host;
      proxy_redirect off;
      proxy_set_header X-Real-IP $remote_addr;
      proxy_set_header X-Scheme $scheme;
      proxy_pass http://127.0.0.1:$1;
    }
  }