I am not sure this still works .. the Content-Length should now be 20
You can also use a more user friendly class WSF_PAGE_RESPONSE   (check descendants of WSF_RESPONSE_MESSAGE)

Note: to inspect all the classes, you can compile /path-to-ewf/tests/all-safe.ecf
This includes the various libs, and examples in a single project ... not executable, but this is nice to browse the entire project inside EiffelStudio.