Dev Mode: Error in WebSocket connection

I keep getting the error “Error in WebSocket connection to ws://localhost:35729/” in the Dev panel.
As I have just a simple HelloWorld page, there’s probably some misconfiguration, but I don’t know how to find it.
Any ideas what to check?


Is there anything in the server logs that could provide more information? If you create a new starter project, do you see that same error?

I just found it: in my run configuration I have this property:
I can’t remember why I added this, but when I change it to true, the error is gone. Is that the expected behaviour?

Now I remember why I disabled the automatic restart: I frequently end up in ClassCastExceptions because classes loaded by RestartClassLoader are in a different module.
What a mess. :unamused:

If you want to disable the live reload altogether, you should remove the Spring Boot Dev Tools dependency (see Live Reload with Spring Boot Developer Tools | Hot Deploy & Live Reload | Configuration | Vaadin Docs), although of course optimally it should work.