Exception: The underlying connection was closed before the hub handshake could complete.

[laimonas]

Hi, tnx for package!

I'm getting this error while trying to connect to hub that's deployed to azure running emulator.
`final connection = HubConnectionBuilder()
.withUrl(
'https://fortestpurpose.azurewebsites.net/hub',
HttpConnectionOptions(
transport: HttpTransportType.webSockets,
logging: (level, message) => print(message),
))
.withAutomaticReconnect()
.build();

await connection.start();`

Using localhost service there is no such error for example with url:
http://10.0.2.2:5000/hub

Any clues why this can happen?

[jamiewest]

Thank you for your issue, would it be possible for you to share the logs when you connect? I did some basic testing with Azure and will probably need to focus some attention here. Thanks!

[laimonas]

Hi there is my logs:

I/flutter (17280): Starting HubConnection.
I/flutter (17280): Starting connection with transfer format 'TransferFormat.text'.
I/flutter (17280): Sending negotiation request: https://scrumpokertest.azurewebsites.net/scrum-poker/negotiate.
D/EGL_emulation(17280): eglMakeCurrent: 0x7992b9ef9dc0: ver 3 0 (tinfo 0x7992b9e32f20)
I/flutter (17280): Selecting transport 'HttpTransportType.webSockets'.
I/flutter (17280): (WebSockets transport) Connecting.
I/flutter (17280): WebSocket connected to wss://scrumpokertest.azurewebsites.net/scrum-poker?id=D0riT29u-hAprZq3ss2DdA.
I/flutter (17280): The HttpConnection connected successfully.
I/flutter (17280): Sending handshake request.
I/flutter (17280): (WebSockets transport) sending data. String data of length '32'.
I/flutter (17280): Using HubProtocol 'json'.
I/flutter (17280): WebSocketChannelException: WebSocketChannelException: WebSocketException: Connection to 'https://scrumpokertest.azurewebsites.net:0/scrum-poker?id=D0riT29u-hAprZq3ss2DdA#' was not upgraded to websocket
I/flutter (17280): (WebSockets transport) socket closed.
I/flutter (17280): HttpConnection.stopConnection(null) called while in state ConnectionState.connected.
I/flutter (17280): Connection disconnected.
I/flutter (17280): HubConnection.connectionClosed(null) called while in state HubConnectionState.disconnected.
I/flutter (17280): Hub handshake failed with error 'Exception: The underlying connection was closed before the hub handshake could complete.' during start(). Stopping HubConnection.
I/flutter (17280): Call to HttpConnection.stop(Exception: The underlying connection was closed before the hub handshake could complete.) ignored because the connection is already in the disconnected state.
I/flutter (17280): HubConnection failed to start successfully because of error '{Exception: The underlying connection was closed before the hub handshake could complete..toString}'.

You can try with this url:
https://scrumpokertest.azurewebsites.net/scrum-poker

[jamiewest]

Just a quick update, I haven't had a chance to start coding a fix yet. The underlying socket is not getting upgraded when connecting. I will need to modify the underlying web_socket_channel library to accept an upgraded socket when not running on the web. I tried testing the web version with your site but failed due to the cors policy. Long polling and server sent events seem to work okay.

[laimonas]

Hi @jamiewest tnx for info. I have tried with long polling and it's working for me also (didn't know about this). If you need my azure signalr site to test from web i can try to configure CORS for you if you need, just ping me here and i will look when i have time.

[jamiewest]

I made some progress but I am not receiving at 503 (service unavailable) error from your backend. Any ideas?

[laimonas]

@jamiewest 503 error is probably because of site is running in free plan only 60 min execution per day. I have upgraded the service plan and it should be online for all day.
Also if you want to test some hub actions there is:

connection.invoke('CreateGroup', args: ['Group name, 'User name']);
connection.on('GroupCreated', (response) async {
});

[jamiewest]

I am waiting to see if a pull request is accepted regarding #387 in package:http/http.dart. If this is accepted then I will be able to provide a mechanism to handle bad certificate callbacks and other security context concerns along with allowing the socket to be upgraded. This should in part resolve the issue your having.

I did end up pushing my own SignalR app in an Azure App Service plan, the free one, to see if I could recreate the problems you are having. During the process it asked specifically if I wanted to enable websockets, which I did. I think yours might me missing this piece, you can check this by going into the app service/configuration/general settings area and make sure the radio button is enabled for web sockets.

[laimonas]

@jamiewest websockets are enabled. I just made another test. I have two apps on azure one is based on windows and other on linux service plan. And yes it is working with windows but not the linux one. So i don't know if this is a bug with library or azure it self. Maybe you can try with linux service plan (it is much cheaper then windows based).

[laimonas]

@jamiewest somehow i cannot reproduce this anymore on linux instance of azure it is even started to work with " transport: HttpTransportType.webSockets". I have also tested with flutter web and it is also working with one thing that i need to disable skipNegotiation. So you can close this one!

[jamiewest]

Okay, thanks. Once the http package is published with my changes I will publish this library with a handful of bug fixes. Hopefully soon...

[sawproduction]

have you solved this I'm getting this error after 2 years of yours

[MathiasTP]

I am getting this error as well..

[aminesnip]

I am getting this error as well.
When I test locally on windows it works very well, but the error appears when I publish on the linux server.
Any solution to fix this problem ?.

[frkn2076]

I was facing the same issue and stopping hubConnection before super.dispose solved my issue.

@override
  void dispose() {
    hubConnection.stop();  // I've added that line.
    super.dispose();
  }

[sinanhaci]

I am getting this error as well. When I test locally on windows it works very well, but the error appears when I publish on the linux server. Any solution to fix this problem ?.

Were you able to solve the problem?

[andres-aranda]

Me enfrentaba al mismo problema y detuve hubConnection antes de que super.dispose resolviera mi problema.

@override
  void dispose() {
    hubConnection.stop();  // I've added that line.
    super.dispose();
  }

eso en que archivo lo agregaste?

[sinanhaci]

This issue usually occurs on Linux servers, in my experience, it's not related to the package itself, but rather to the server configurations.

[mamaly12]

I still have the same issue. I use IdentityServer 4, and the following setup is recommended for signal authentication using the access token(according to https://learn.microsoft.com/en-us/aspnet/core/signalr/authn-and-authz?view=aspnetcore-7.0#identity-server-jwt-authentication).

It's not related to the OS, and I am suspicious it's related to the library that cannot update the connection.

  var originalOnMessageReceived = options.Events.OnMessageReceived;
            options.Events.OnMessageReceived = async context =>
            {
                await originalOnMessageReceived(context);

                if (string.IsNullOrEmpty(context.Token))
                {
                    var accessToken = context.Request.Query["access_token"];
                    var path = context.HttpContext.Request.Path;

                    if (!string.IsNullOrEmpty(accessToken) &&
                        path.StartsWithSegments("/hubs"))
                    {
                        context.Token = accessToken;
                    }
                }
            };

When I start a socket connection request, everything seems fine, and the " context.Token" will be set according to the token. Still, suddenly, I received the error "The underlying connection was closed before the hub handshake could complete." from Flutter and my connection will be closed

[madagaskarr]

I think the issue is on the server, try changing the connection protocol to long pooling

[kivocsa99]

@madagaskarr
iam having the same issue what do you mean by changing it to long pooling and how to do that ?

[kivocsa99]

@jamiewest
any updates on this ?

[madagaskarr]

I fixed this on the nginx server by adding support to upgrade the connection. The library work as expected!

[kivocsa99]

@madagaskarr iam using IIS any suggestions ?

[DmitryGaimaldinov]

In my case the problem happened only when I was using [Authrize] attribute in hub.
I added JwtBearerEvents handler, and everything started working.

builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddJwtBearer(JwtBearerDefaults.AuthenticationScheme, options =>
        {
            options.TokenValidationParameters = new TokenValidationParameters
            {
                ...
            };
            options.MapInboundClaims = false;
            options.Events = new JwtBearerEvents
            {
                OnMessageReceived = context =>
                {
                    var path = context.Request.Path;
                    var accessToken = context.Request.Query["access_token"];
                   // Here also was a check "path.StartsWithSegments("/hubs")" like the documentations suggests, but it caused websocket error so I removed it
                    if (!string.IsNullOrEmpty(accessToken))
                    {

                        context.Request.Headers.Add("Authorization", new[] { $"Bearer {accessToken}" });
                    }
                    return Task.CompletedTask;
                }
            };
        });