SignalR Java client unable to open WebSocket

Describe the bug

I’m unable to connect to a ASP.NET Core SignalR hub from the Java client. I’ll specify all versions of things below to hopefully make this more understandable.

Every time I start the HubConnection object, I get the following error:

Aug 08, 2019 4:21:12 PM com.microsoft.signalr.OkHttpWebSocketWrapper$SignalRWebSocketListener onFailure
SEVERE: WebSocket closed from an error: Expected HTTP 101 response but was '200 OK'.
Aug 08, 2019 4:21:12 PM com.microsoft.signalr.WebSocketTransport onClose
INFO: WebSocket connection stopping with code null and reason 'Expected HTTP 101 response but was '200 OK''.
Aug 08, 2019 4:21:12 PM com.microsoft.signalr.HubConnection stopConnection
SEVERE: HubConnection disconnected with an error Expected HTTP 101 response but was '200 OK'.
Aug 08, 2019 4:21:12 PM com.microsoft.signalr.HubConnection stopConnection
INFO: HubConnection stopped.

---

I’ve confirmed that WebSockets are enabled on the hub (as I can see it as an option returned during the negotiation phase), eg:

{
    "connectionId": "...",
    "availableTransports": [
        {
            "transport": "WebSockets",
            "transferFormats": [
                "Text",
                "Binary"
            ]
        },
        {
            "transport": "ServerSentEvents",
            "transferFormats": [
                "Text"
            ]
        },
        {
            "transport": "LongPolling",
            "transferFormats": [
                "Text",
                "Binary"
            ]
        }
    ]
}

I’ve also tried setting shouldSkipNegotiate() on the Java client, and making sure that only the WebSocket transport was configured for the hub, but that yielded the same result.

---

To Reproduce

Versions

• Microsoft.AspNetCore.App 2.2.0
• Microsoft.AspNetCore.SignalR 1.1.0
• Java 1.8.0_77
• com.microsoft.signalr 3.0.0-preview7.19365.7

1. Build a HubConnection object, with an access token provider. Eg:

hubConnection = HubConnectionBuilder.create("http://localhost:52929/rtc")
    	.withAccessTokenProvider(Single.defer(() -> {
    		String token = getToken("username", "password"); // token fetch logic
    		return Single.just(token);
    	}))
    	.build();

1. Start the HubConnection
2. Receive the error above

Expected behavior

I expect the client to connect to the hub, and receive messages.

Additional context

I originally picked this issue up while writing a module for a 3rd party product, with an embedded SignalR client. I’ve replicated this in a standalone Java program though, so I’m rolling with the standalone program until I can confirm it works without any interference from the 3rd party product.

Include the output of dotnet --info

.NET Core SDK (reflecting any global.json):
 Version:   2.2.401
 Commit:    729b316c13

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.17763
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\2.2.401\

Host (useful for support):
  Version: 2.2.6
  Commit:  7dac9b1b51

.NET Core SDKs installed:
  2.1.202 [C:\Program Files\dotnet\sdk]
  2.1.401 [C:\Program Files\dotnet\sdk]
  2.1.403 [C:\Program Files\dotnet\sdk]
  2.1.502 [C:\Program Files\dotnet\sdk]
  2.1.700 [C:\Program Files\dotnet\sdk]
  2.2.101 [C:\Program Files\dotnet\sdk]
  2.2.103 [C:\Program Files\dotnet\sdk]
  2.2.300 [C:\Program Files\dotnet\sdk]
  2.2.401 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.3-servicing-26724-03 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]

[Stoolbend]

Sure. So try running in Kestrel perhaps?

[Stoolbend]

Ok I’ve got it now. In my web.config file, I had a rule that handled HTML5 routes for the SPA website that it hosts. It had some exclusions in for the /api/* and /health endpoints, but not for the SignalR endpoints. Entirely my fault for this one.😞

<rule name="html5-routes" stopProcessing="true">
  <match url=".*" />
  <!-- Handle all paths except /api/ and pass the route onto the wwwroot/index.html -->
  <conditions logicalGrouping="MatchAll">
    <add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true" />
    <!-- Add rule to negate file requests e.g. css/html/images-->
    <add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true" />
    <!-- Add rule to negate directories-->
    <add input="{REQUEST_URI}" pattern="^/api/|^/health" negate="true" />
    <!-- Add rule to negate paths and let them through the MVC-->
    <add input="{HTTP_METHOD}" pattern="GET|HEAD" />
  </conditions>
  <action type="Rewrite" url="wwwroot/index.html" />
</rule>

After I added |^/rtc|^/metadata to the “Add rule to negate directories” section, it started working in IIS Express.

At least that explains why it was working in Kestrel, and not IIS Express (or I imagine IIS if I was to test using that).