title: Jupyter notebook kernel not connecting
body: <p>I have previously used <code>Jupyter Notebook</code> (python 2 and 3) on my mac. After not using it for a while, there seems to be a problem I am unable to fix. When starting the notebook from terminal using the command <code>Jupyter notebook</code>, and then select a notebook I want to work with, I get the error: </p>
  
  <pre><code>"A connection to the notebook server could not be established. The notebook will continue trying to reconnect. Check your network connection or notebook server configuration."
  </code></pre>
  
  <p>I am positive this has nothing to do with my internet connection (I have tried 2 machines connected to different networks).</p>
  
  <p>I have read that the browser could be the problem, therefore I have installed Chrome and Firefox. However, I get this error when I am using Safari, Chrome, and Firefox. </p>
  
  <p>Then I read about it being a proxy issue. I have tried to add the server address of the notebook to the <code>No proxy fields</code> of the advanced network preferences of my mac, and of the advanced setting on Firefox. </p>
  
  <p>The only thing I can think of is that I am entering the wrong server address? </p>
  
  <p>I do not know much about setting and errors in general, hopefully someone can provide me with some alternative options to get Jupyter working again. </p>
  
  <p>Terminal output:</p>
  
  <pre><code>ValueError: signal only works in main thread
  ERROR:tornado.application:Exception in callback &lt;functools.partial object at 0x111e2b208&gt;
  Traceback (most recent call last):
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/tornado/ioloop.py", line 759, in _run_callback
      ret = callback()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/tornado/stack_context.py", line 276, in null_wrapper
      return fn(*args, **kwargs)
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/zmq/eventloop/zmqstream.py", line 536, in &lt;lambda&gt;
      self.io_loop.add_callback(lambda : self._handle_events(self.socket, 0))
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/zmq/eventloop/zmqstream.py", line 450, in _handle_events
      self._handle_recv()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/zmq/eventloop/zmqstream.py", line 480, in _handle_recv
      self._run_callback(callback, msg)
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/zmq/eventloop/zmqstream.py", line 432, in _run_callback
      callback(*args, **kwargs)
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/tornado/stack_context.py", line 276, in null_wrapper
      return fn(*args, **kwargs)
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/ipykernel/kernelbase.py", line 283, in dispatcher
      return self.dispatch_shell(stream, msg)
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/ipykernel/kernelbase.py", line 233, in dispatch_shell
      self.pre_handler_hook()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/ipykernel/kernelbase.py", line 248, in pre_handler_hook
      self.saved_sigint_handler = signal(SIGINT, default_int_handler)
  ValueError: signal only works in main thread
  [I 19:03:26.685 NotebookApp] KernelRestarter: restarting kernel (1/5), new random ports
  Traceback (most recent call last):
    File "/Users/xxx/anaconda2/lib/python2.7/runpy.py", line 174, in _run_module_as_main
      "__main__", fname, loader, pkg_name)
    File "/Users/xxx/anaconda2/lib/python2.7/runpy.py", line 72, in _run_code
      exec code in run_globals
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/ipykernel_launcher.py", line 16, in &lt;module&gt;
      app.launch_new_instance()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/traitlets/config/application.py", line 658, in launch_instance
      app.start()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/ipykernel/kernelapp.py", line 477, in start
      ioloop.IOLoop.instance().start()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/tornado/ioloop.py", line 928, in start
      raise RuntimeError("IOLoop is already running")
  RuntimeError: IOLoop is already running
  [I 19:03:29.696 NotebookApp] KernelRestarter: restarting kernel (2/5), new random ports
  Traceback (most recent call last):
    File "/Users/xxx/anaconda2/lib/python2.7/runpy.py", line 174, in _run_module_as_main
      "__main__", fname, loader, pkg_name)
    File "/Users/xxx/anaconda2/lib/python2.7/runpy.py", line 72, in _run_code
      exec code in run_globals
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/ipykernel_launcher.py", line 16, in &lt;module&gt;
      app.launch_new_instance()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/traitlets/config/application.py", line 658, in launch_instance
      app.start()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/ipykernel/kernelapp.py", line 477, in start
      ioloop.IOLoop.instance().start()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/tornado/ioloop.py", line 928, in start
      raise RuntimeError("IOLoop is already running")
  RuntimeError: IOLoop is already running
  [I 19:03:32.712 NotebookApp] KernelRestarter: restarting kernel (3/5), new random ports
  Traceback (most recent call last):
    File "/Users/xxx/anaconda2/lib/python2.7/runpy.py", line 174, in _run_module_as_main
      "__main__", fname, loader, pkg_name)
    File "/Users/xxx/anaconda2/lib/python2.7/runpy.py", line 72, in _run_code
      exec code in run_globals
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/ipykernel_launcher.py", line 16, in &lt;module&gt;
      app.launch_new_instance()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/traitlets/config/application.py", line 658, in launch_instance
      app.start()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/ipykernel/kernelapp.py", line 477, in start
      ioloop.IOLoop.instance().start()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/tornado/ioloop.py", line 928, in start
      raise RuntimeError("IOLoop is already running")
  RuntimeError: IOLoop is already running
  [W 19:03:33.717 NotebookApp] Timeout waiting for kernel_info reply from 2cf24420-719b-4666-ad9f-fcdf8db505f3
  [E 19:03:33.721 NotebookApp] Uncaught exception in /api/kernels/2cf24420-719b-4666-ad9f-fcdf8db505f3/channels
      Traceback (most recent call last):
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/tornado/websocket.py", line 498, in _run_callback
          result = callback(*args, **kwargs)
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/notebook/services/kernels/handlers.py", line 262, in open
          super(ZMQChannelsHandler, self).open()
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/notebook/base/zmqhandlers.py", line 176, in open
          self.send_ping, self.ping_interval, io_loop=loop,
      TypeError: __init__() got an unexpected keyword argument 'io_loop'
  [E 19:03:34.749 NotebookApp] Uncaught exception in /api/kernels/2cf24420-719b-4666-ad9f-fcdf8db505f3/channels
      Traceback (most recent call last):
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/tornado/websocket.py", line 498, in _run_callback
          result = callback(*args, **kwargs)
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/notebook/services/kernels/handlers.py", line 262, in open
          super(ZMQChannelsHandler, self).open()
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/notebook/base/zmqhandlers.py", line 176, in open
          self.send_ping, self.ping_interval, io_loop=loop,
      TypeError: __init__() got an unexpected keyword argument 'io_loop'
  [I 19:03:35.724 NotebookApp] KernelRestarter: restarting kernel (4/5), new random ports
  [E 19:03:35.771 NotebookApp] Uncaught exception in /api/kernels/2cf24420-719b-4666-ad9f-fcdf8db505f3/channels
      Traceback (most recent call last):
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/tornado/websocket.py", line 498, in _run_callback
          result = callback(*args, **kwargs)
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/notebook/services/kernels/handlers.py", line 262, in open
          super(ZMQChannelsHandler, self).open()
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/notebook/base/zmqhandlers.py", line 176, in open
          self.send_ping, self.ping_interval, io_loop=loop,
      TypeError: __init__() got an unexpected keyword argument 'io_loop'
  Traceback (most recent call last):
    File "/Users/xxx/anaconda2/lib/python2.7/runpy.py", line 174, in _run_module_as_main
      "__main__", fname, loader, pkg_name)
    File "/Users/xxx/anaconda2/lib/python2.7/runpy.py", line 72, in _run_code
      exec code in run_globals
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/ipykernel_launcher.py", line 16, in &lt;module&gt;
      app.launch_new_instance()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/traitlets/config/application.py", line 658, in launch_instance
      app.start()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/ipykernel/kernelapp.py", line 477, in start
      ioloop.IOLoop.instance().start()
    File "/Users/xxx/anaconda2/lib/python2.7/site-packages/tornado/ioloop.py", line 928, in start
      raise RuntimeError("IOLoop is already running")
  RuntimeError: IOLoop is already running
  [E 19:03:36.791 NotebookApp] Uncaught exception in /api/kernels/2cf24420-719b-4666-ad9f-fcdf8db505f3/channels
      Traceback (most recent call last):
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/tornado/websocket.py", line 498, in _run_callback
          result = callback(*args, **kwargs)
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/notebook/services/kernels/handlers.py", line 262, in open
          super(ZMQChannelsHandler, self).open()
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/notebook/base/zmqhandlers.py", line 176, in open
          self.send_ping, self.ping_interval, io_loop=loop,
      TypeError: __init__() got an unexpected keyword argument 'io_loop'
  [E 19:03:37.810 NotebookApp] Uncaught exception in /api/kernels/2cf24420-719b-4666-ad9f-fcdf8db505f3/channels
      Traceback (most recent call last):
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/tornado/websocket.py", line 498, in _run_callback
          result = callback(*args, **kwargs)
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/notebook/services/kernels/handlers.py", line 262, in open
          super(ZMQChannelsHandler, self).open()
        File "/Users/xxx/anaconda2/lib/python2.7/site-packages/notebook/base/zmqhandlers.py", line 176, in open
          self.send_ping, self.ping_interval, io_loop=loop,
      TypeError: __init__() got an unexpected keyword argument 'io_loop'
  [W 19:03:38.733 NotebookApp] KernelRestarter: restart failed
  [W 19:03:38.733 NotebookApp] Kernel 2cf24420-719b-4666-ad9f-fcdf8db505f3 died, removing from map.
  [W 19:03:38.830 NotebookApp] 404 GET /api/kernels/2cf24420-719b-4666-ad9f-fcdf8db505f3/channels?session_id=3F75F379F865488D8379D3BB7FC0BF0F (::1): Kernel does not exist: 2cf24420-719b-4666-ad9f-fcdf8db505f3
  [W 19:03:38.838 NotebookApp] 404 GET /api/kernels/2cf24420-719b-4666-ad9f-fcdf8db505f3/channels?session_id=3F75F379F865488D8379D3BB7FC0BF0F (::1) 12.00ms referer=None
  [W 19:03:40.859 NotebookApp] Replacing stale connection: 2cf24420-719b-4666-ad9f-fcdf8db505f3:3F75F379F865488D8379D3BB7FC0BF0F
  </code></pre>