Howdy, Jim! Thanks for your support of my book! This new topic isn't in the current edition of the book, but it will be covered in the next update to the ebook.
To enable your extension to view WebSocket traffic, write an inspector which implements the IResponseInspector2 and IWSMInspector interfaces. This latter interface has one method, AssignMessage(WebSocketMessage oWSM); your code should inspect the message when this method is called.