Update WebSocket URL

[IvoneDjaja]

Referencing the WebSocket documentation https://websocket.org/reference/websocket-api/, the correct echo server URL is now wss://echo.websocket.org.

Fixes: #13182

PRs or commits this PR depends on (if any):

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[gemini-code-assist]

Code Review

This pull request updates the WebSocket echo server URL. While the new URL is correct, the change has been applied directly to a documentation file that contains code excerpts from a source file. This has resulted in an incomplete update, as the old URL still exists in other parts of the documentation and in the source example file itself. My review provides guidance on how to apply this change correctly in the source file to ensure consistency.

[parlough]

/gcbrun

[flutter-website-bot]

Visit the preview URL for this PR (updated for commit dacb64f):

https://flutter-docs-prod--pr13183-patch-2-7p60pgu9.web.app

[parlough]

Thanks for catching and updating this!

I believe it was the .org version originally then that stopped working at some point, but looks like it's back again.