remove superfluous ws-hostname parameter from notebook

This made the notebook server artificially and unnecessarily brittle to tunneling, and non-local hostname resolution.  The ws_url is now defined based on the Origin of the request.  This allows tunneled hosts and ports to preserve connections, as the ws_url always matches the one in use by the client.

Implemented as a property, to facilitate future cases where it might behave differently.

IPython/frontend/html/notebook/handlers.py

@@ -139,7 +139,15 @@ class AuthenticatedHandler(web.RequestHandler):
                 return True
         else:
             return False
+    
+    @property
+    def ws_url(self):
+        """websocket url matching the current request
         
+        turns http[s]://host[:port]/foo/bar into
+                ws[s]://host[:port]/foo/bar
+        """
+        return self.request.headers.get('Origin').replace('http', 'ws', 1)
 
 
 class ProjectDashboardHandler(AuthenticatedHandler):
@@ -221,8 +229,7 @@ class MainKernelHandler(AuthenticatedHandler):
         km = self.application.kernel_manager
         notebook_id = self.get_argument('notebook', default=None)
         kernel_id = km.start_kernel(notebook_id)
-        ws_url = self.application.ipython_app.get_ws_url()
-        data = {'ws_url':ws_url,'kernel_id':kernel_id}
+        data = {'ws_url':self.ws_url,'kernel_id':kernel_id}
         self.set_header('Location', '/'+kernel_id)
         self.finish(jsonapi.dumps(data))
 
@@ -249,8 +256,7 @@ class KernelActionHandler(AuthenticatedHandler):
             self.set_status(204)
         if action == 'restart':
             new_kernel_id = km.restart_kernel(kernel_id)
-            ws_url = self.application.ipython_app.get_ws_url()
-            data = {'ws_url':ws_url,'kernel_id':new_kernel_id}
+            data = {'ws_url':self.ws_url,'kernel_id':new_kernel_id}
             self.set_header('Location', '/'+new_kernel_id)
             self.write(jsonapi.dumps(data))
         self.finish()

IPython/frontend/html/notebook/notebookapp.py

@@ -147,7 +147,6 @@ aliases.update({
     'port': 'NotebookApp.port',
     'keyfile': 'NotebookApp.keyfile',
     'certfile': 'NotebookApp.certfile',
-    'ws-hostname': 'NotebookApp.ws_hostname',
     'notebook-dir': 'NotebookManager.notebook_dir',
 })
 
@@ -155,7 +154,7 @@ aliases.update({
 # multi-kernel evironment:
 aliases.pop('f', None)
 
-notebook_aliases = [u'port', u'ip', u'keyfile', u'certfile', u'ws-hostname',
+notebook_aliases = [u'port', u'ip', u'keyfile', u'certfile',
                     u'notebook-dir']
 
 #-----------------------------------------------------------------------------
@@ -200,13 +199,6 @@ class NotebookApp(BaseIPythonApplication):
         help="The port the notebook server will listen on."
     )
 
-    ws_hostname = Unicode(LOCALHOST, config=True,
-        help="""The FQDN or IP for WebSocket connections. The default will work
-                fine when the server is listening on localhost, but this needs to
-                be set if the ip option is used. It will be used as the hostname part
-                of the WebSocket url: ws://hostname/path."""
-    )
-
     certfile = Unicode(u'', config=True, 
         help="""The full path to an SSL/TLS certificate file."""
     )
@@ -226,14 +218,6 @@ class NotebookApp(BaseIPythonApplication):
         help="Whether to prevent editing/execution of notebooks."
     )
 
-    def get_ws_url(self):
-        """Return the WebSocket URL for this server."""
-        if self.certfile:
-            prefix = u'wss://'
-        else:
-            prefix = u'ws://'
-        return prefix + self.ws_hostname + u':' + unicode(self.port)
-
     def parse_command_line(self, argv=None):
         super(NotebookApp, self).parse_command_line(argv)
         if argv is None: