Blazor Server side app Failed to connect via WebSockets

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Blazor Server side app Failed to connect via WebSockets

John Woakes 20

I have a Blazor web app that used to run fine in Azure. The latest deployment does not work. It works fine locally on my development machine. Looking at the developer tools in Chrome I see this message:

[2023-01-18T19:02:18.263Z] Warning: Failed to connect via WebSockets, using the Long Polling fallback transport. This may be due to a VPN or proxy blocking the connection. To troubleshoot this, visit https://aka.ms/blazor-server-using-fallback-long-polling.

log @ blazor.server.js:1

[Violation] 'setInterval' handler took 138ms

I have tried different browsers and different machines. The app loads but only shows basic layout without any data.

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Ryan Hill 30,281 Microsoft Employee Moderator

Hey @John Woakes based on the error message, I would check to make sure that Web Sockets weren't disabled for your app service. If you're not familiar with this setting, it's in General Settings under the Configuration blade.

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If it's enabled, then check for any firewall rules or NSGs that may have inadvertently applied to your app service. If none are applied, then we'll need to work more closely with you regarding this matter. You can reach out to me via email to AzCommunity[at]microsoft[dot]com ATTN: Ryan. Make sure you include your app service name and a link to this post.

John Woakes 20 Reputation points

2023-01-23T03:55:54.5566667+00:00

I checked that setting and it was on. I have since set up Azure SignalR Service and that seems to fix this problem. It seems like overkill for my simple app but it is free for how much I use it so I am moving on.
Ryan Hill 30,281 Reputation points Microsoft Employee Moderator

2023-02-18T05:58:29.86+00:00

Hi @John Woakes , were you able to determine any configuration changes that were made prior to that latest deployment? Are you still using SignalR service as the workaround?
John Woakes 20 Reputation points

2023-02-18T21:20:30.8966667+00:00

I am still using the SignalR service. I haven't had the time do dig into this any further I am afraid...
Ryan Hill 30,281 Reputation points Microsoft Employee Moderator

2023-02-20T23:45:29.9666667+00:00

@John Woakes send me an email to AzCommunity[at]microsoft[dot]com ATTN: Ryan with enclosed with a link to this post and your app service name so I can investigate a little deeper.

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Blazor Server side app Failed to connect via WebSockets

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