Connection closed with an error. Unknown error

Web socket connection to Azure services returns error after trying to connect from several browser tabs:

{"type":7,"error":"Connection closed with an error."}

Several tabs succeed to connect to sockets and receive mesages, but most of connections returned this type of error. I have no clue what is going wrong because no error description returned.

I am using Azure services on Free plan, but dashboard shows that all is under the message/connection limits (max 18 connections):

I have tried to configure signalR options EnableDetailedErrors, but with no result - no error description. Startup.cs:

services.AddSignalR(conf =>
{
    conf.HandshakeTimeout = TimeSpan.FromSeconds(300);
    conf.EnableDetailedErrors = true;
})
.AddAzureSignalR(configure => 
{
    configure.ConnectionString = connString;
    configure.ConnectionCount = 1;
    configure.AccessTokenLifetime = TimeSpan.FromHours(24);
});

app.UseAuthentication();
app.UseMvc();
app.UseFileServer();              

app.UseAzureSignalR(routes =>
{
    routes.MapHub<ChatHub>("/hub/chat");
});

Javascript client:

var connection = new HubConnectionBuilder()
      .withUrl('/hun/chat', { accessTokenFactory: () => this.authService.getAccessToken() })
      .build();
connection.serverTimeoutInMilliseconds = 300000;
connection.start();

Microsoft.AspNetCore.SignalR: 1.0.2 Microsoft.Azure.SignalR: 1.0.0-preview1-10015

[xscript]

Then it is probably just intermittent network issue. I will close this issue for now. Feel free to reopen it or create another issue if you have further questions.

[ToniaDemchuk]

Thank you for reply. I cannot reproduce it anymore. Debug logs don’t show any suspicious items.