2010
2009
Tornado Web Server Documentation
by greutTornado comes with limited support for WSGI. However, since WSGI does not support non-blocking requests, you cannot use any of the asynchronous/non-blocking features of Tornado in your application if you choose to use WSGI instead of Tornado's HTTP server. Some of the features that are not available in WSGI applications: @tornado.web.asynchronous, the httpclient module, and the auth module.
in other words: WSGI sucks
evserver - Google Code
by greutEvServer is a lightweight http server, created especially to host python WSGI applications. Additionally, it supports little known Asynchronous WSGI extension, which was suggested by Christopher Stawarz. Using this extension it's possible to create an output html response in many data chunks, without blocking the main server process while your application waits for external resources.
Comet the WSGI way.