Tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed. By using non-blocking network I/O, Tornado can scale to tens of thousands of open connections, making it ideal for long polling, WebSockets, and other applications that require a long-lived connection to each user.

Open Source: yes, Apache-2.0
Source: https://pypi.python.org/pypi/tornado
Why: needed as dependency of gns3