How to resolve ERROR NetworkError at XMLHttpRequest.send (…dist\fxcore\server\main.js:200768:19)

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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 && 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.

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)```

20 thoughts on “How to resolve ERROR NetworkError at XMLHttpRequest.send (…dist\fxcore\server\main.js:200768:19)”

  1. I am getting the same error. Try to remove TransferHttpCacheModule from your app.module and create your own custom http transfer interceptor file.

    I made a file called transfer-state.interceptor.ts and then added it to app.module providers:[] to handle this. The examples below will show how I hooked it up. I am not sure if this will definitely work for you but it did make that error go away for me.

    
//app.module.ts

import { BrowserModule, BrowserTransferStateModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { HttpClientModule, HTTP_INTERCEPTORS } from "@angular/common/http";
//import {TransferHttpCacheModule } from '@nguniversal/common';

import { AppRoutingModule } from './app-routing/app-routing.module';
import { AppComponent } from './app.component';
import { HomeComponent } from './modules/home/home.component';
import { SliderComponent } from './components/slider/slider.component';
import { WindowRefService } from './services/window-ref.service';
//import { TransferHttpInterceptorService } from './services/transfer-http-interceptor.service';
import { TransferStateInterceptor } from './interceptors/transfer-state.interceptor';
import { ServiceWorkerModule } from '@angular/service-worker';
import { environment } from '../environments/environment';

@NgModule({
  declarations: [
    AppComponent,
    HomeComponent,
    SliderComponent
  ],
  imports: [
    BrowserModule.withServerTransition({ appId: 'serverApp' }),
    BrowserTransferStateModule,
    AppRoutingModule,
    HttpClientModule,
    ServiceWorkerModule.register('ngsw-worker.js', { enabled: environment.production })
  ],
  providers: [
    WindowRefService,
    {
      provide: HTTP_INTERCEPTORS,
      useClass: TransferStateInterceptor,
      multi: true
    }
],
  bootstrap: [AppComponent]
})
export class AppModule { }

    This is one version of a custom transfer state file but there are a few ways to do this if this one doesn’t work.

    
//transfer-state.interceptor.ts

import { HttpEvent, HttpHandler, HttpInterceptor, HttpRequest, HttpResponse } from '@angular/common/http';
import { Inject, Injectable, PLATFORM_ID } from '@angular/core';
import { Observable, of } from 'rxjs';
import { StateKey, TransferState, makeStateKey } from '@angular/platform-browser';
import { isPlatformBrowser, isPlatformServer } from '@angular/common';
import { tap } from 'rxjs/operators';

@Injectable()
export class TransferStateInterceptor implements HttpInterceptor {

  constructor(
    private transferState: TransferState,
    @Inject(PLATFORM_ID) private platformId: any,
  ) {}

  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {

    // For this demo application, we will only worry about State Transfer for get requests.
    if (request.method !== 'GET') {
      return next.handle(request);
    }


    // Use the request url as the key.
    const stateKey: StateKey<string> = makeStateKey<string>(request.url);

    // For any http requests made on the server, store the response in State Transfer.
    if (isPlatformServer(this.platformId)) {
      return next.handle(request).pipe(
        tap((event: HttpResponse<any>) => {
          this.transferState.set(stateKey, event.body);
        })
      );
    }

    // For any http requests made in the browser, first check State Transfer for a 
    // response corresponding to the request url.
    if (isPlatformBrowser(this.platformId)) {
      const transferStateResponse = this.transferState.get<any>(stateKey, null);
      if (transferStateResponse) {
        const response = new HttpResponse({ body: transferStateResponse, status: 200 });

        // Remove the response from state transfer, so any future requests to 
        // the same url go to the network (this avoids us creating an 
        // implicit/unintentional caching mechanism).
        this.transferState.remove(stateKey);
        return of(response);
      } else {
        return next.handle(request);
      }
    }
  }
}

    If you want to add custom cache to this you can by installing memory-cache but I haven’t tried that out yet. For more references these articles helped me out a lot and maybe they can help you too.

    https://itnext.io/angular-universal-caching-transferstate-96eaaa386198

    https://willtaylor.blog/angular-universal-for-angular-developers/

    https://bcodes.io/blog/post/angular-universal-relative-to-absolute-http-interceptor

    If you haven’t you may need to add ServerTransferStateModule to your app.server.module file.

    
//app.server.module

import { NgModule } from '@angular/core';
import {
  ServerModule,
  ServerTransferStateModule
} from "@angular/platform-server";

import { AppModule } from './app.module';
import { AppComponent } from './app.component';

@NgModule({
  imports: [
    AppModule,
    ServerModule,
    ServerTransferStateModule
  ],
  bootstrap: [AppComponent],
})
export class AppServerModule {}

    good luck!

    Reply

  2. I was still getting this ERROR NetworkError but I found another way to make this error go away. I think this answer is relevant since I was getting the same error posted above. If this can help anyone with that same server error then that’s great.

    If the api request is made to the server OnInit when reloading check isPlatformBrowser first when using ng-universal example.

    import { Component, OnInit, PLATFORM_ID, Inject } from '@angular/core';
import { isPlatformBrowser } from '@angular/common';
import { HttpClient, HttpHeaders } from '@angular/common/http';

public testBrowser: boolean;
export class HomeComponent implements OnInit {

  public testBrowser  : boolean;
  public data         : any;
  
  constructor(private http: HttpClient, @Inject(PLATFORM_ID) platformId: string) {
    this.testBrowser = isPlatformBrowser(platformId);
  }

  ngOnInit() {
    if (this.testBrowser) {
      //avoid server NETWORK error
      this.data = this.http.get('/api');
    }
  }
}

    I was getting this same error trying to make server calls from the client before checking isPlatformBrowser === true first OnInit and this solved my problem. Hopefully this can help this bug.

    For reference this answer helped me squash this long standing bug. https://stackoverflow.com/a/46893433/4684183

    Reply

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