When a WSGI application returns an iterable that has a .close() method, the server is supposed to call that method once the request has finished.  The wsgiref server does not do this when a client disconnects from a streaming response.

The attached script allows testing the .close() behavior of various wsgi servers (wsgiref, cherrypy, gevent, werkzeug, and gunicorn).  wsgiref is the only one of the tested implementations that does not call .close().