SignalR Asp.netcore and angular ( WebSocket is not in the OPEN state) disconnection for signalR.HttpTransportType.WebSockets

Question

Using .NET Core 2.2 and Angular 8 with package "@aspnet/signalr": "^1.1.4". I have set up a hub in .NET Core 2.2 which works fine with another Angular project using the same package.

Startup.cs:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using SignalrChat.Services;

namespace SignalrChat
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddCors(o => o.AddPolicy("CorsPolicy", builder =>
            {
                builder
                .AllowAnyHeader()
                .AllowAnyMethod()
                .SetIsOriginAllowed(_ => true)
                .AllowCredentials();
            }));
            services.AddSignalR();
            services.AddSingleton<IChatRoomService, InMemoryChatRoomService>();
            services.AddControllers();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseRouting();

            app.UseAuthorization();

            app.UseCors("CorsPolicy");
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
                endpoints.MapHub<ChatHub>("/chat");
            });
        }
    }
}

Hub:

using Microsoft.AspNetCore.SignalR;
using SignalrChat.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace SignalrChat
{
    public class ChatHub : Hub
    {}
}

Angular:

import * as signalR from "@aspnet/signalr";
import {
  Component, Inject, OnInit
} from '@angular/core';

import { DeviceDetectorService } from 'ngx-device-detector';
import { DOCUMENT } from '@angular/common';
import { Router } from '@angular/router';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {
    ngOnInit(): void {
        this.hub = new signalR.HubConnectionBuilder()
            .configureLogging(signalR.LogLevel. Trace)
        .withUrl('http://localhost:56328/chat')
        
            .build();

        this.hub.serverTimeoutInMilliseconds = 100000;
        this.hub.keepAliveIntervalInMilliseconds = 100000;
        this.hub
            .start()
            .then(() => {  
                console.log('Connection started!');
                console.log('Getting all rooms');  

            })
            .catch(err => {
                console.log(err);
                console.log(this.hub);
                
            });
    }
}

Here is the log for hub.start() from Angular project that works fine:

[2019-12-31T11:43:30.214Z] Debug: Starting HubConnection.
Utils.js:213 [2019-12-31T11:43:30.215Z] Debug: Starting connection with transfer format 'Text'.
Utils.js:213 [2019-12-31T11:43:30.220Z] Debug: Sending negotiation request: http://localhost:56328/chat/negotiate.
Utils.js:213 [2019-12-31T11:43:31.382Z] Debug: Selecting transport 'WebSockets'.
client:52 [WDS] Live Reloading enabled.
Utils.js:209 [2019-12-31T11:43:32.001Z] Information: WebSocket connected to ws://localhost:56328/chat?id=NafCuVY_brPNmqQlN2EvXw.
Utils.js:213 [2019-12-31T11:43:32.003Z] Debug: Sending handshake request.
Utils.js:209 [2019-12-31T11:43:32.006Z] Information: Using HubProtocol 'json'.
Utils.js:213 [2019-12-31T11:43:32.053Z] Debug: Server handshake complete.

But for the other angular project with the exact same code and package to the same hub, it cannot proceed. Here is the log:

[2019-12-31T11:41:35.294Z] Debug: Starting HubConnection.
Utils.js:213 [2019-12-31T11:41:35.639Z] Debug: Starting connection with transfer format 'Text'.
Utils.js:213 [2019-12-31T11:41:35.644Z] Debug: Sending negotiation request: http://localhost:56328/chat/negotiate.
core.js:16829 Angular is running in the development mode. Call enableProdMode() to enable the production mode.
Utils.js:213 [2019-12-31T11:41:36.574Z] Debug: Selecting transport 'WebSockets'.
WebSocket connection to 'ws://localhost:4200/sockjs-node/694/1skccdzm/websocket' failed: WebSocket is closed before the connection is established.
[2019-12-31T11:41:38.814Z] Information: WebSocket connected to ws://localhost:56328/chat?id=qO3s36husX9-boU1SwyaBg.
Utils.js:213 [2019-12-31T11:41:38.820Z] Debug: Sending handshake request.
app.component.ts:34 WebSocket is not in the OPEN state

I tried to change all the packages of the "not-wroking angular" to the same as the "working-angular", the problem still remains.

UPDATE

I found out that changing http transport mode of signalR.HubConnectionBuilder() will get it worked as below:

var options = {
    transport: signalR.HttpTransportType.ServerSentEvents ,
    logging: signalR.LogLevel.Trace, 
};
this.hub = new signalR.HubConnectionBuilder()
    //.withUrl('http://localhost:56328/chat' , options)
    .withUrl('http://localhost:49941/chat', options) 
    .build();

ServerSentEvent is successful, yet the websocket and longpolling modes are not.

Answer 1

Thanks to @Fei Han for mentioning this useful solution: it worked when i changed my code to this:

 Object.defineProperty(WebSocket, 'OPEN', { value: 1, }); 
        this.hub
            .start()
            .then(() => {                     
                console.log('Connection started!');         

            })
            .catch(err => {
                console.log(err);                     
            });