title: jquery S.post and xmlhttprequest both do not give back result accessing localhost web server
body: <p>I have developed a web server based on mqtt emqx which saves IoT data in a Sqlite3 DB accessed by a local http sever python made on port 8080 to which a emqtx plugin routes data coming from connected IoT devices. So far so good. Now the problem is to fetch those data via nginx server on port 80 without a direct ws connection to the db handler not to expose it to internet but instead getting the data via html page under nginx calling the http python server on port 8080 by jQuery $.post or xmlhttprequest either. The bad news is that the call is executed on the python http server but the result is not received back by the jQuery call which gives error instead.</p>
  
  <p>If I send the request to the http python server by a node.js client or by a python requests client everything is fine so I do not understand why the access made by jquery in the browser can't get the result. Currently my application is working fine accessing the DB driver by web socket but I wanted to avoid exposing the DB access in the net. Any suggestion is appreciated.</p>
  
  <p>Note: All above stuff runs in a Linux Docker container</p>