Document WebSocket support for threading mode

Author: miguelgrinberg

docs/server.rst

@@ -59,7 +59,7 @@ Socket.IO servers to integrate easily into existing WSGI or ASGI applications::
 Serving Static Files
 --------------------
 
-The Engine.IO server can be configured to serve static files to clients. This
+The Socket.IO server can be configured to serve static files to clients. This
 is particularly useful to deliver HTML, CSS and JavaScript files to clients
 when this package is used without a companion web framework.
 
@@ -832,8 +832,7 @@ Standard Threads
 While not comparable to eventlet and gevent in terms of performance,
 the Socket.IO server can also be configured to work with multi-threaded web
 servers that use standard Python threads. This is an ideal setup to use with
-development servers such as `Werkzeug <http://werkzeug.pocoo.org>`_. Only the
-long-polling transport is currently available when using standard threads.
+development servers such as `Werkzeug <http://werkzeug.pocoo.org>`_.
 
 Instances of class ``socketio.Server`` will automatically use the threading
 mode if neither eventlet nor gevent are not installed. To request the
@@ -854,15 +853,22 @@ development web server based on Werkzeug::
     # ... Socket.IO and Flask handler functions ...
 
     if __name__ == '__main__':
-        app.run(threaded=True)
+        app.run()
+
+The example that follows shows how to start an Socket.IO application using
+Gunicorn's threaded worker class::
+
+    $ gunicorn -w 1 --threads 100 module:app
 
-When using the threading mode, it is important to ensure that the WSGI server
-can handle multiple concurrent requests using threads, since a client can have
-up to two outstanding requests at any given time. The Werkzeug server is
-single-threaded by default, so the ``threaded=True`` option is required.
+With the above configuration the server will be able to handle up to 100
+concurrent clients.
 
-Note that servers that use worker processes instead of threads, such as
-gunicorn, do not support a Socket.IO server configured in threading mode.
+When using standard threads, WebSocket is supported through the
+`simple-websocket <https://github.com/miguelgrinberg/simple-websocket>`_
+package, which must be installed separately. This package provides a
+multi-threaded WebSocket server that is compatible with Werkzeug and Gunicorn's
+threaded worker. Other multi-threaded web servers are not supported and will
+not enable the WebSocket transport.
 
 Scalability Notes
 ~~~~~~~~~~~~~~~~~