无法连接到测试服务器。“错误连接被拒绝“

Question

我是Django的新手，正在尝试通过python3 manage.py runserver运行测试服务器。我得到消息说一切都很顺利：

Performing system checks...

System check identified no issues (0 silenced).

You have 15 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.

January 28, 2019 - 19:15:50
Django version 2.1.5, using settings 'mytestsite.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.

不过，当我试图从Chrome浏览器连接到http://127.0.0.1:8000/时，我得到的信息是无法访问该网站。我在Ubuntu上的防火墙配置：

Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing), disabled (routed)
New profiles: skip

To                         Action      From
--                         ------      ----
22/tcp (OpenSSH)           ALLOW IN    Anywhere
8000                       ALLOW IN    Anywhere
Anywhere                   ALLOW IN    127.0.0.1
22/tcp (OpenSSH (v6))      ALLOW IN    Anywhere (v6)
8000 (v6)                  ALLOW IN    Anywhere (v6)

还有什么问题吗？这是我的第一套。谢谢你的帮助。你知道吗