Tutorial Part 1: Basic Setup
============================

In this tutorial we will build a simple chat server. It will have two pages:

* An index view that lets you type the name of a chat room to join.
* A room view that lets you see messages posted in a particular chat room.

The room view will use a WebSocket to communicate with the Django server and
listen for any messages that are posted.

We assume that you are familiar with basic concepts for building a Django site.
If not we recommend you complete `the Django tutorial`_ first and then come back 
to this tutorial.

We assume that you have `Django installed`_ already. You can tell Django is
installed and which version by running the following command in a shell prompt
(indicated by the ``$`` prefix)::

    $ python3 -m django --version

We also assume that you have :doc:`Channels installed </installation>` already. You can tell
Channels is installed by running the following command::

    $ python3 -c 'import channels; print(channels.__version__)'

This tutorial is written for Channels 2.0, which supports Python 3.5+ and Django
1.11+. If the Channels version does not match, you can refer to the tutorial for
your version of Channels by using the version switcher at the bottom left corner
of this page, or update Channels to the newest version.

This tutorial also **uses Docker** to install and run Redis. We use Redis as the
backing store for the channel layer, which is an optional component of the
Channels library that we use in the tutorial. `Install Docker`_ from its
official website - there are official runtimes for Mac OS and Windows that
make it easy to use, and packages for many Linux distributions where it can
run natively.

.. note::
    While you can run the standard Django ``runserver`` without the need
    for Docker, the channels features we'll be using in later parts of the
    tutorial will need Redis to run, and we recommend Docker as the easiest
    way to do this.

.. _the Django tutorial: https://docs.djangoproject.com/en/stable/intro/tutorial01/
.. _Django installed: https://docs.djangoproject.com/en/stable/intro/install/

.. _Install Docker: https://www.docker.com/get-docker

Creating a project
------------------

If you don't already have a Django project, you will need to create one.

From the command line, ``cd`` into a directory where you'd like to store your
code, then run the following command::

    $ django-admin startproject mysite

This will create a ``mysite`` directory in your current directory with the 
following contents::

    mysite/
        manage.py
        mysite/
            __init__.py
            settings.py
            urls.py
            wsgi.py

Creating the Chat app
---------------------

We will put the code for the chat server in its own app.

Make sure you're in the same directory as ``manage.py`` and type this command::

    $ python3 manage.py startapp chat

That'll create a directory ``chat``, which is laid out like this::

    chat/
        __init__.py
        admin.py
        apps.py
        migrations/
            __init__.py
        models.py
        tests.py
        views.py

For the purposes of this tutorial, we will only be working with ``chat/views.py`` 
and ``chat/__init__.py``. So remove all other files from the ``chat`` directory.

After removing unnecessary files, the ``chat`` directory should look like::

    chat/
        __init__.py
        views.py

We need to tell our project that the ``chat`` app is installed. Edit the
``mysite/settings.py`` file and add ``'chat'`` to the **INSTALLED_APPS** setting.
It'll look like this::

    # mysite/settings.py
    INSTALLED_APPS = [
        'chat',
        'django.contrib.admin',
        'django.contrib.auth',
        'django.contrib.contenttypes',
        'django.contrib.sessions',
        'django.contrib.messages',
        'django.contrib.staticfiles',
    ]

Add the index view
------------------

We will now create the first view, an index view that lets you type the name of
a chat room to join.

Create a ``templates`` directory in your ``chat`` directory. Within the
``templates`` directory you have just created, create another directory called
``chat``, and within that create a file called ``index.html`` to hold the
template for the index view.

Your chat directory should now look like::

    chat/
        __init__.py
        templates/
            chat/
                index.html
        views.py

Put the following code in ``chat/templates/chat/index.html``::

    <!-- chat/templates/chat/index.html -->
    <!DOCTYPE html>
    <html>
    <head>
        <meta charset="utf-8"/>
        <title>Chat Rooms</title>
    </head>
    <body>
        What chat room would you like to enter?<br/>
        <input id="room-name-input" type="text" size="100"/><br/>
        <input id="room-name-submit" type="button" value="Enter"/>
        
        <script>
            document.querySelector('#room-name-input').focus();
            document.querySelector('#room-name-input').onkeyup = function(e) {
                if (e.keyCode === 13) {  // enter, return
                    document.querySelector('#room-name-submit').click();
                }
            };

            document.querySelector('#room-name-submit').onclick = function(e) {
                var roomName = document.querySelector('#room-name-input').value;
                window.location.pathname = '/chat/' + roomName + '/';
            };
        </script>
    </body>
    </html>

Create the view function for the room view.
Put the following code in ``chat/views.py``::

    # chat/views.py
    from django.shortcuts import render
    
    def index(request):
        return render(request, 'chat/index.html', {})

To call the view, we need to map it to a URL - and for this we need a URLconf.

To create a URLconf in the chat directory, create a file called ``urls.py``.
Your app directory should now look like::

    chat/
        __init__.py
        templates/
            chat/
                index.html
        urls.py
        views.py

In the ``chat/urls.py`` file include the following code::

    # chat/urls.py
    from django.urls import path
    
    from . import views
    
    urlpatterns = [
        path('', views.index, name='index'),
    ]

The next step is to point the root URLconf at the **chat.urls** module.
In ``mysite/urls.py``, add an import for **django.conf.urls.include** and
insert an **include()** in the **urlpatterns** list, so you have::

    # mysite/urls.py
    from django.conf.urls import include
    from django.urls import path
    from django.contrib import admin
    
    urlpatterns = [
        path('chat/', include('chat.urls')),
        path('admin/', admin.site.urls),
    ]

Let's verify that the index view works. Run the following command::

    $ python3 manage.py runserver

You'll see the following output on the command line::

    Performing system checks...

    System check identified no issues (0 silenced).

    You have 13 unapplied migration(s). Your project may not work properly until you apply the migrations for app(s): admin, auth, contenttypes, sessions.
    Run 'python manage.py migrate' to apply them.

    February 18, 2018 - 22:08:39
    Django version 1.11.10, using settings 'mysite.settings'
    Starting development server at http://127.0.0.1:8000/
    Quit the server with CONTROL-C.

Go to http://127.0.0.1:8000/chat/ in your browser and you should see the text
"What chat room would you like to enter?" along with a text input to provide a
room name.

Type in "lobby" as the room name and press enter. You should be redirected to
the room view at http://127.0.0.1:8000/chat/lobby/ but we haven't written the
room view yet, so you'll get a "Page not found" error page.

Go to the terminal where you ran the ``runserver`` command and press Control-C
to stop the server.

Integrate the Channels library
------------------------------

So far we've just created a regular Django app; we haven't used the Channels
library at all. Now it's time to integrate Channels.

Let's start by creating a root routing configuration for Channels. A Channels
:doc:`routing configuration </topics/routing>` is similar to a Django URLconf in that it tells Channels
what code to run when an HTTP request is received by the Channels server.

We'll start with an empty routing configuration.
Create a file ``mysite/routing.py`` and include the following code::

    # mysite/routing.py
    from channels.routing import ProtocolTypeRouter

    application = ProtocolTypeRouter({
        # (http->django views is added by default)
    })

Now add the Channels library to the list of installed apps.
Edit the ``mysite/settings.py`` file and add ``'channels'`` to the
``INSTALLED_APPS`` setting. It'll look like this::

    # mysite/settings.py
    INSTALLED_APPS = [
        'channels',
        'chat',
        'django.contrib.admin',
        'django.contrib.auth',
        'django.contrib.contenttypes',
        'django.contrib.sessions',
        'django.contrib.messages',
        'django.contrib.staticfiles',
    ]

You'll also need to point Channels at the root routing configuration.
Edit the ``mysite/settings.py`` file again and add the following to the bottom
of it::

    # mysite/settings.py
    # Channels
    ASGI_APPLICATION = 'mysite.routing.application'

With Channels now in the installed apps, it will take control of the
``runserver`` command, replacing the standard Django development server with
the Channels development server.

.. note::
    The Channels development server will conflict with any other third-party
    apps that require an overloaded or replacement runserver command.
    An example of such a conflict is with `whitenoise.runserver_nostatic`_ from
    `whitenoise`_. In order to solve such issues, try moving ``channels`` to the
    top of your ``INSTALLED_APPS`` or remove the offending app altogether.

.. _whitenoise.runserver_nostatic: https://github.com/evansd/whitenoise/issues/77
.. _whitenoise: https://github.com/evansd/whitenoise

Let's ensure that the Channels development server is working correctly.
Run the following command::

    $ python3 manage.py runserver

You'll see the following output on the command line::

    Performing system checks...
    
    System check identified no issues (0 silenced).
    
    You have 13 unapplied migration(s). Your project may not work properly until you apply the migrations for app(s): admin, auth, contenttypes, sessions.
    Run 'python manage.py migrate' to apply them.
    
    February 18, 2018 - 22:16:23
    Django version 1.11.10, using settings 'mysite.settings'
    Starting ASGI/Channels development server at http://127.0.0.1:8000/
    Quit the server with CONTROL-C.
    2018-02-18 22:16:23,729 - INFO - server - HTTP/2 support not enabled (install the http2 and tls Twisted extras)
    2018-02-18 22:16:23,730 - INFO - server - Configuring endpoint tcp:port=8000:interface=127.0.0.1
    2018-02-18 22:16:23,731 - INFO - server - Listening on TCP address 127.0.0.1:8000

.. note::
    Ignore the warning about unapplied database migrations.
    We won't be using a database in this tutorial.

Notice the line beginning with 
``Starting ASGI/Channels development server at http://127.0.0.1:8000/``. 
This indicates that the Channels development server has taken over from the
Django development server.

Go to http://127.0.0.1:8000/chat/ in your browser and you should still see the
index page that we created before.

Go to the terminal where you ran the ``runserver`` command and press Control-C
to stop the server.

This tutorial continues in :doc:`Tutorial 2 </tutorial/part_2>`.