Blazor WebAssembly SignalR does not use WebSocket transport in net5.0-rc1

[campersau]

Describe the bug

When using Blazor WebAssembly SignalR does not use WebSocket transport but Long Polling instead.

To Reproduce

Checkout https://github.com/campersau/blazor-signalr-test which includes a server and clients (important file is Index.razor). Looking at the dev tools only long polling fetch requests are being made and no websocket connection.

HAR file

Console output when adding logging to SignalR client:

Microsoft.AspNetCore.Http.Connections.Client.Internal.LongPollingTransport: Starting transport. Transfer mode: Text.
Microsoft.AspNetCore.Http.Connections.Client.HttpConnection: HttpConnection Started.
Microsoft.AspNetCore.SignalR.Client.HubConnection: Using HubProtocol 'json v1'.
Microsoft.AspNetCore.SignalR.Client.HubConnection: HubConnection started.

Further technical details

• ASP.NET Core version: 5.0.100-rc.1.20452.10
• Microsoft Visual Studio Enterprise 2019 Preview Version 16.8.0 Preview 3.0

[Pilchie]

👀

[ar0311]

Can someone point me to why WebSockets are no longer supported on Blazor WASM?

[campersau]

@ar0311 see the corresponding PR #25922
So SignalR WebSockets should finally work again in rc2.

Standalone WebSockets should work now though.

[msschl]

Same issue for me

[BrennanConroy]

Fixed via #25922