title: Airflow: Can't connect to ('0.0.0.0', 8080)
body: <p>I am on Ubuntu 16.04,I have installed Airflow with pip. Next step</p>
  
  <pre><code>airflow initdb
  [2017-07-29 12:20:23,483] {__init__.py:57} INFO - Using executor SequentialExecutor
  DB: sqlite:////home/milenko/airflow/airflow.db
  [2017-07-29 12:20:23,813] {db.py:287} INFO - Creating tables
  INFO  [alembic.runtime.migration] Context impl SQLiteImpl.
  </code></pre>
  
  <p>This works fine.But when I try to start webserver</p>
  
  <pre><code>airflow webserver -p 8080
  [2017-07-29 12:20:45,913] [4585] {models.py:167} INFO - Filling up the DagBag from /home/milenko/airflow/dags
  Running the Gunicorn Server with:
  Workers: 4 sync
  Host: 0.0.0.0:8080
  Timeout: 120
  Logfiles: - -
  =================================================================            
  [2017-07-29 12:20:46,950] {__init__.py:57} INFO - Using executor SequentialExecutor
  [2017-07-29 12:20:47 +0200] [4590] [INFO] Starting gunicorn 19.3.0
  [2017-07-29 12:20:47 +0200] [4590] [ERROR] Connection in use: ('0.0.0.0', 8080)
  [2017-07-29 12:20:47 +0200] [4590] [ERROR] Retrying in 1 second.
  [2017-07-29 12:20:48 +0200] [4590] [ERROR] Connection in use: ('0.0.0.0', 8080)
  [2017-07-29 12:20:48 +0200] [4590] [ERROR] Retrying in 1 second.
  [2017-07-29 12:20:49 +0200] [4590] [ERROR] Connection in use: ('0.0.0.0', 8080)
  [2017-07-29 12:20:49 +0200] [4590] [ERROR] Retrying in 1 second.
  [2017-07-29 12:20:50 +0200] [4590] [ERROR] Connection in use: ('0.0.0.0', 8080)
  [2017-07-29 12:20:50 +0200] [4590] [ERROR] Retrying in 1 second.
  [2017-07-29 12:20:51 +0200] [4590] [ERROR] Connection in use: ('0.0.0.0', 8080)
  [2017-07-29 12:20:51 +0200] [4590] [ERROR] Retrying in 1 second.
  [2017-07-29 12:20:52 +0200] [4590] [ERROR] Can't connect to ('0.0.0.0', 8080)
  </code></pre>
  
  <p>How to solve this?Is this Gunicorn Server issue or not?
  With netstat I got this output</p>
  
  <pre><code>sudo netstat -nlp | grep :80
  tcp6       0      0 :::8080                 :::*                    LISTEN      1711/java
  </code></pre>
  
  <p>As I understand the port is in use.But what is 1711/java?If I turn it off will it affect something else?
  This is the relevant part of my airflow configuration file</p>
  
  <pre><code>[webserver]
  # The base url of your website as airflow cannot guess what domain or
  # cname you are using. This is used in automated emails that
  # airflow sends to point links to the right web server
  base_url = http://localhost:8080
  
  # The ip specified when starting the web server
  web_server_host = 0.0.0.0
  
  # The port on which to run the web server
  web_server_port = 8080
  
  # Paths to the SSL certificate and key for the web server. When both are
  # provided SSL will be enabled. This does not change the web server port.
  web_server_ssl_cert =
  web_server_ssl_key =
  
  # Number of seconds the gunicorn webserver waits before timing out on a worker
  web_server_worker_timeout = 120
  
  # Number of workers to refresh at a time. When set to 0, worker refresh is
  # disabled. When nonzero, airflow periodically refreshes webserver workers by
  # bringing up new ones and killing old ones.
  worker_refresh_batch_size = 1
  
  # Number of seconds to wait before refreshing a batch of workers.
  worker_refresh_interval = 30
  
  # Secret key used to run your flask app
  secret_key = temporary_key
  
  # Number of workers to run the Gunicorn web server
  workers = 4
  
  # The worker class gunicorn should use. Choices include
  # sync (default), eventlet, gevent
  worker_class = sync
  </code></pre>