upstream ip_host_addr{
       server 127.0.0.1:8081;
    }

   server {
       listen 80;
       server_name abc.def.com;
       client_max_body_size  300m;

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