Quickstart ========== Here's a quick working example of how Flask-SSE works. .. warning:: `Server-sent events`_ do *not* work with Flask's built-in development server, because it handles HTTP requests one at a time. The SSE stream is intended to be an infinite stream of events, so it will never complete. If you try to run this code on with the built-in development server, the server will be unable to take any other requests once you connect to this stream. Instead, you must use a web server with asychronous workers. Gunicorn_ can work with gevent_ to use asychronous workers: see :ref:`gunicorn's design documentation `. You will also need a Redis_ server running locally for this example to work. Make a virtual environment and install Flask-SSE, ``gunicorn``, and ``gevent``. You will also need to make sure you have a Redis_ server running locally. .. code-block:: bash $ pyvenv sse $ pip install flask-sse gunicorn gevent Make a file on your computer called ``sse.py``, with the following content: .. code-block:: python from flask import Flask, render_template from flask_sse import sse app = Flask(__name__) app.config["REDIS_URL"] = "redis://localhost" app.register_blueprint(sse, url_prefix='/stream') @app.route('/') def index(): return render_template("index.html") @app.route('/hello') def publish_hello(): sse.publish({"message": "Hello!"}, type='greeting') return "Message sent!" If you are using a Redis server that has a password use:: app.config["REDIS_URL"] = "redis://:password@localhost" Make a ``templates`` folder next to ``sse.py``, and create a file named ``index.html`` in that folder, with the following content: .. code-block:: html Flask-SSE Quickstart

Flask-SSE Quickstart

Run your code using gunicorn's gevent workers: .. code-block:: bash $ gunicorn sse:app --worker-class gevent --bind Open your web browser, and visit ````. Your web browser will automatically connect to the server-sent event stream. Open another tab, and visit ````. You should get a Javascript alert in the first tab when you do so. .. _Server-sent events: https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events .. _Redis: http://www.redis.io/ .. _gunicorn: http://gunicorn.org/ .. _gevent: http://www.gevent.org/