Follow the steps here: https://spring.io/quickstart

Add spring dev tools as a dependency during project configuration here https://start.spring.io/

Use 2.5.2 version

Install Live reload extension for Chrome: https://chrome.google.com/webstore/detail/livereload/jnihajbhpnppcggbcgedagnkighmdlei/related

Run the app using mvn spring-boot:run. Open browser http://localhost:8080/hello.

Click on the Live reload extension button.

There will be an error shown in the popup : see attached image.

The problem is : JS WebSocket class can't connect to the server.

If I write the code in the Chrome console ws = new WebSocket("ws://localhost:35729"); then it fails with error.

Everything works fine with 2.5.1 version.

Screen Shot 2021-07-05 at 1 33 33 PM

Comment From: wilkinsona

Thanks for the report and sorry for the inconvenience. I suspect that this regression is caused by the changes for https://github.com/spring-projects/spring-boot/pull/26813. Specifically, I think the lower-casing has corrupted the value of the sec-websocket-key header.

Comment From: denis-anisimov

Most likely yes.