GWT developer mode code server

The GWT developer mode embedded http server makes all the sense in the world to me but I confess I do not understand what the "code server" is all about. It strikes me that an html file wraps all the javascript code the browser ne开发者_开发问答eds to render the GWT application with the embedded Jetty server handling AJAX during development. So I'm looking for an explanation for including a developer mode code server with GWT. Maybe an explanation of what it is doing will suffice.

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As usual, official docs to the rescue!

When an application is running in development mode, the Java Virtual Machine (JVM) is actually executing the application code as compiled Java bytecode, using GWT plumbing to connect to a browser window. This means that the debugging facilities of your IDE are available to debug both your client-side GWT code and any server-side Java code as well. By remaining in this traditional "code-test-debug" cycle, development mode is by far the most productive way to develop your application quickly.