.. title:: Tornado Web Server

.. meta::
    :google-site-verification: g4bVhgwbVO1d9apCUsT-eKlApg31Cygbp8VGZY8Rf0g

|Tornado Web Server|
====================

.. |Tornado Web Server| image:: tornado.png
    :alt: Tornado Web Server

`Tornado <http://www.tornadoweb.org>`_ is a Python web framework and
asynchronous networking library, originally developed at `FriendFeed
<http://friendfeed.com>`_.  By using non-blocking network I/O, Tornado
can scale to tens of thousands of open connections, making it ideal for
`long polling <http://en.wikipedia.org/wiki/Push_technology#Long_polling>`_,
`WebSockets <http://en.wikipedia.org/wiki/WebSocket>`_, and other
applications that require a long-lived connection to each user.


Quick links
-----------

* :doc:`Documentation <documentation>`
* |Download current version|: :current_tarball:`z` (:doc:`release notes <releases>`)
* `Source (github) <https://github.com/facebook/tornado>`_
* `Mailing list <http://groups.google.com/group/python-tornado>`_
* `Wiki <https://github.com/facebook/tornado/wiki/Links>`_

.. |Download current version| replace:: Download version |version|

Hello, world
------------

Here is a simple "Hello, world" example web app for Tornado::

    import tornado.ioloop
    import tornado.web

    class MainHandler(tornado.web.RequestHandler):
        def get(self):
            self.write("Hello, world")

    application = tornado.web.Application([
        (r"/", MainHandler),
    ])

    if __name__ == "__main__":
        application.listen(8888)
        tornado.ioloop.IOLoop.instance().start()

This example does not use any of Tornado's asynchronous features; for
that see this `simple chat room
<https://github.com/facebook/tornado/tree/master/demos/chat>`_.

Installation
------------

**Automatic installation**::

    pip install tornado

Tornado is listed in `PyPI <http://pypi.python.org/pypi/tornado>`_ and
can be installed with ``pip`` or ``easy_install``.  Note that the
source distribution includes demo applications that are not present
when Tornado is installed in this way, so you may wish to download a
copy of the source tarball as well.

**Manual installation**: Download :current_tarball:`z`:

.. parsed-literal::

    tar xvzf tornado-|version|.tar.gz
    cd tornado-|version|
    python setup.py build
    sudo python setup.py install

The Tornado source code is `hosted on GitHub
<https://github.com/facebook/tornado>`_.

**Prerequisites**: Tornado runs on Python 2.6, 2.7, 3.2, and 3.3.  It has
no strict dependencies outside the Python standard library, although some
features may require one of the following libraries:

* `unittest2 <https://pypi.python.org/pypi/unittest2>`_ is needed to run
  Tornado's test suite on Python 2.6 (it is unnecessary on more recent
  versions of Python)
* `concurrent.futures <https://pypi.python.org/pypi/futures>`_ is the
  recommended thread pool for use with Tornado and enables the use of
  `~tornado.netutil.ThreadedResolver`.  It is needed only on Python 2;
  Python 3 includes this package in the standard library.
* `pycurl <http://pycurl.sourceforge.net>`_ is used by the optional
  ``tornado.curl_httpclient``.  Libcurl version 7.18.2 or higher is required;
  version 7.21.1 or higher is recommended.
* `Twisted <http://www.twistedmatrix.com>`_ may be used with the classes in
  `tornado.platform.twisted`.
* `pycares <https://pypi.python.org/pypi/pycares>`_ is an alternative
  non-blocking DNS resolver that can be used when threads are not
  appropriate.
* `Monotime <https://pypi.python.org/pypi/Monotime>`_ adds support for
  a monotonic clock, which improves reliability in environments
  where clock adjustments are frequent.  No longer needed in Python 3.3.

**Platforms**: Tornado should run on any Unix-like platform, although
for the best performance and scalability only Linux (with ``epoll``)
and BSD (with ``kqueue``) are recommended (even though Mac OS X is
derived from BSD and supports kqueue, its networking performance is
generally poor so it is recommended only for development use).

Discussion and support
----------------------

You can discuss Tornado on `the Tornado developer mailing list
<http://groups.google.com/group/python-tornado>`_, and report bugs on
the `GitHub issue tracker
<https://github.com/facebook/tornado/issues>`_.  Links to additional
resources can be found on the `Tornado wiki
<https://github.com/facebook/tornado/wiki/Links>`_.

Tornado is one of `Facebook's open source technologies
<http://developers.facebook.com/opensource/>`_. It is available under
the `Apache License, Version 2.0
<http://www.apache.org/licenses/LICENSE-2.0.html>`_.

This web site and all documentation is licensed under `Creative
Commons 3.0 <http://creativecommons.org/licenses/by/3.0/>`_.

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   documentation