Forum Discussion
NimbostratusAPM webtop – problem with websockets for Serverside Blazor app
Dear community,
We have a web application built with Blazor server side rendering that utilizes SignalR (websockets) and runs on a Windows server with IIS (i.e. not web assembly).
Virtual sever: the site runs as intended!
Webtop + virtual sever: The site will render and SSO works, but any page using SignalR will loose interactivity as the websocket handshake times out.
We have tried to disable websockets on the server which makes SignalR use long polling as a fallback. The web browser displays a different error message but behaves the same otherwise (have not dug deeper as we intend to use websockets in production).
I would greatly appreciate any guidance on what to do!
This is the log from the blazor web app (behind webtop + virtual server):
2025-09-18 16:50:26 Debug Microsoft.AspNetCore.SignalR.Internal.DefaultHubProtocolResolver Registered SignalR Protocol: json, implemented by Microsoft.AspNetCore.SignalR.Protocol.JsonHubProtocol.
2025-09-18 16:50:26 Debug Microsoft.AspNetCore.SignalR.Internal.DefaultHubProtocolResolver Registered SignalR Protocol: blazorpack, implemented by Microsoft.AspNetCore.Components.Server.BlazorPack.BlazorPackHubProtocol.
2025-09-18 16:50:27 Debug Microsoft.AspNetCore.Http.Connections.Internal.HttpConnectionManager New connection XQNqGM4oGkm0P1v4NECJ9g created.
2025-09-18 16:50:27 Debug Microsoft.AspNetCore.Http.Connections.Internal.HttpConnectionDispatcher Sending negotiation response.
2025-09-18 16:50:27 Debug Microsoft.AspNetCore.Http.Connections.Internal.HttpConnectionDispatcher Establishing new connection.
2025-09-18 16:50:27 Debug Microsoft.AspNetCore.SignalR.HubConnectionHandler OnConnectedAsync started.
2025-09-18 16:50:27 Debug Microsoft.AspNetCore.Http.Connections.Internal.Transports.WebSocketsTransport Socket opened using Sub-Protocol: '(null)'.
2025-09-18 16:50:42 Debug Microsoft.AspNetCore.SignalR.HubConnectionContext Handshake was canceled.
2025-09-18 16:50:42 Debug Microsoft.AspNetCore.Http.Connections.Internal.Transports.WebSocketsTransport Waiting for the client to close the socket.
2025-09-18 16:50:42 Debug Microsoft.AspNetCore.Http.Connections.Internal.Transports.WebSocketsTransport Socket closed.
2025-09-18 16:50:42 Debug Microsoft.AspNetCore.Http.Connections.Internal.HttpConnectionManager Removing connection xVt0cL2a0gpMOiJROyJxhw from the list of connections.
This is the log from the same blazor web app when it works as intended
2025-09-18 17:29:31 Debug Microsoft.AspNetCore.SignalR.Internal.DefaultHubProtocolResolver Registered SignalR Protocol: json, implemented by Microsoft.AspNetCore.SignalR.Protocol.JsonHubProtocol.
2025-09-18 17:29:31 Debug Microsoft.AspNetCore.SignalR.Internal.DefaultHubProtocolResolver Registered SignalR Protocol: blazorpack, implemented by Microsoft.AspNetCore.Components.Server.BlazorPack.BlazorPackHubProtocol.
2025-09-18 17:29:37 Debug Microsoft.AspNetCore.Http.Connections.Internal.HttpConnectionManager New connection c0CR_c-7xa0QydeddE5HcA created.
2025-09-18 17:29:37 Debug Microsoft.AspNetCore.Http.Connections.Internal.HttpConnectionDispatcher Sending negotiation response.
2025-09-18 17:29:37 Debug Microsoft.AspNetCore.SignalR.HubConnectionHandler OnConnectedAsync started.
2025-09-18 17:29:37 Debug Microsoft.AspNetCore.Http.Connections.Internal.Transports.WebSocketsTransport Socket opened using Sub-Protocol: '(null)'.
2025-09-18 17:29:37 Debug Microsoft.AspNetCore.SignalR.Internal.DefaultHubProtocolResolver Found protocol implementation for requested protocol: blazorpack.
2025-09-18 17:29:37 Debug Microsoft.AspNetCore.SignalR.HubConnectionContext Completed connection handshake. Using HubProtocol 'blazorpack'.
2025-09-18 17:29:37 Debug Microsoft.AspNetCore.SignalR.Internal.DefaultHubDispatcher Received hub invocation: InvocationMessage { InvocationId: "0", Target: "StartCircuit", Arguments: [ https://testsite.com/, https://testsite.com/counter, [], CfD...m ], StreamIds: [ ] }.
2025-09-18 17:29:37 Debug Microsoft.AspNetCore.SignalR.Internal.DefaultHubDispatcher Received hub invocation: InvocationMessage { InvocationId: "", Target: "EndInvokeJSFromDotNet", Arguments: [ 2, True, [2,true,null] ], StreamIds: [ ] }.
2025-09-18 17:29:37 Debug Microsoft.AspNetCore.SignalR.Internal.DefaultHubDispatcher Received hub invocation: InvocationMessage { InvocationId: "", Target: "UpdateRootComponents", Arguments: [ {"batchId":1,"operations":[{"type":"add","ssrComponentId":1,"marker":{"type":"server","prerenderId":"80...9c8","key":{"locationHash":"....","formattedComponentKey":""},"sequence":0,"descriptor":".... ], StreamIds: [ ] }.
2025-09-18 17:29:37 Debug Microsoft.AspNetCore.SignalR.Internal.DefaultHubDispatcher Received hub invocation: InvocationMessage { InvocationId: "", Target: "OnRenderCompleted", Arguments: [ 2, ], StreamIds: [ ] }.
This is the output in the web browser console when accessing the site via (webtop + virtual server):
2025-09-18T14:50:28.565Z Information: Normalizing '_blazor' to 'https://testsite.com/f5-w-68747470733a2f2f6d6139392e6d6963726f2d746573742e696e747261$$/f5-h-$$/_blazor'. blazor.web.js?F5CH=J:1
2025-09-18T14:50:28.609Z Information: WebSocket connected to wss://testsite.com/f5-w-68747470733a2f2f6d6139392e6d6963726f2d746573742e696e747261$$/f5-h-$$/_blazor?id=xVt0cL2a0gpMOiJROyJxhw. blazor.web.js?F5CH=J:1
2025-09-18T14:50:43.620Z Error: Connection disconnected with error 'Error: Server returned handshake error: Handshake was canceled.'. blazor.web.js?F5CH=J:1
2025-09-18T14:50:43.620Z Error: Error: Server returned handshake error: Handshake was canceled. blazor.web.js?F5CH=J:1
2025-09-18T14:50:43.620Z Error: Failed to start the circuit. blazor.web.js?F5CH=J:1
