title: How to resolve ERROR NetworkError at XMLHttpRequest.send (...dist\fxcore\server\main.js:200768:19)
body: <p>I am new to Angular. I just finished developing my angular web application. When I use ng serve to serve my application during production, everything works fine. I added angular universal. Now when I run any of npm run dev:ssr or npm run build:ssr &amp;&amp; npm run serve:ssr, my application will refuse to open, throwing NetworkError response in the console. I noticed this error occurs for the number of times http requests where sent via class 'constructors(){..}'. I have browsed through several solution but couldn't get a clue of what I'm not doing right. My backend is developed with nodejs and express. I'll appreciate any help I can get.
  Here is a full example of the error response I always get in the console.</p>
  
  <pre><code>ERROR NetworkError
      at XMLHttpRequest.send (C:\Users\MRBEN\Desktop\Angular\fxcore\dist\fxcore\server\main.js:200768:19)
      at Observable._subscribe (C:\Users\MRBEN\Desktop\Angular\fxcore\dist\fxcore\server\main.js:19025:17)
      at Observable._trySubscribe (C:\Users\MRBEN\Desktop\Angular\fxcore\dist\fxcore\server\main.js:186304:25)
      at Observable.subscribe (C:\Users\MRBEN\Desktop\Angular\fxcore\dist\fxcore\server\main.js:186290:22)
      at scheduleTask (C:\Users\MRBEN\Desktop\Angular\fxcore\dist\fxcore\server\main.js:105897:32)
      at Observable._subscribe (C:\Users\MRBEN\Desktop\Angular\fxcore\dist\fxcore\server\main.js:105959:13)
      at Observable._trySubscribe (C:\Users\MRBEN\Desktop\Angular\fxcore\dist\fxcore\server\main.js:186304:25)
      at Observable.subscribe (C:\Users\MRBEN\Desktop\Angular\fxcore\dist\fxcore\server\main.js:186290:22)
      at subscribeToResult (C:\Users\MRBEN\Desktop\Angular\fxcore\dist\fxcore\server\main.js:196385:23)
      at MergeMapSubscriber._innerSub (C:\Users\MRBEN\Desktop\Angular\fxcore\dist\fxcore\server\main.js:191575:116)```
  </code></pre>