restore websocket_url configurable

allows ws to be handled via separate proxies,
as appears to be the case on OpenShift and some other hosting services.

IPython/html/base/handlers.py

@@ -127,6 +127,10 b' class IPythonHandler(AuthenticatedHandler):'
     @property
     def base_url(self):
         return self.settings.get('base_url', '/')
+
+    @property
+    def ws_url(self):
+        return self.settings.get('websocket_url', '')
     
     #---------------------------------------------------------------
     # Manager objects
@@ -215,6 +219,7 b' class IPythonHandler(AuthenticatedHandler):'
     def template_namespace(self):
         return dict(
             base_url=self.base_url,
+            ws_url=self.ws_url,
             logged_in=self.logged_in,
             login_available=self.login_available,
             static_url=self.static_url,

IPython/html/notebookapp.py

@@ -172,6 +172,7 b' class NotebookWebApplication(web.Application):'
 
             # IPython stuff
             nbextensions_path = ipython_app.nbextensions_path,
+            websocket_url=ipython_app.websocket_url,
             mathjax_url=ipython_app.mathjax_url,
             config=ipython_app.config,
             jinja2_env=env,
@@ -512,6 +513,13 b' class NotebookApp(BaseIPythonApplication):'
     def _nbextensions_path_default(self):
         return [os.path.join(get_ipython_dir(), 'nbextensions')]
 
+    websocket_url = Unicode("", config=True,
+        help="""The base URL for websockets,
+        if it differs from the HTTP server (hint: it almost certainly doesn't).
+        
+        Should be in the form of an HTTP origin: ws[s]://hostname[:port]
+        """
+    )
     mathjax_url = Unicode("", config=True,
         help="""The url for MathJax.js."""
     )

IPython/html/static/notebook/js/main.js

@@ -43,6 +43,7 b' require(['
 
     var common_options = {
         base_url : utils.get_body_data("baseUrl"),
+        ws_url : IPython.utils.get_body_data("wsUrl"),
         notebook_path : utils.get_body_data("notebookPath"),
         notebook_name : utils.get_body_data('notebookName')
     };

IPython/html/static/services/kernels/js/kernel.js

@@ -23,6 +23,11 b' define(['
         this.stdin_channel = null;
         this.kernel_service_url = kernel_service_url;
         this.name = name;
+        this.ws_url = IPython.utils.get_body_data("wsUrl");
+        if (!this.ws_url) {
+            // trailing 's' in https will become wss for secure web sockets
+            this.ws_url = location.protocol.replace('http', 'ws') + "//" + location.host;
+        }
         this.running = false;
         this.username = "username";
         this.session_id = utils.uuid();
@@ -122,8 +127,6 b' define(['
         console.log("Kernel started: ", json.id);
         this.running = true;
         this.kernel_id = json.id;
-        // trailing 's' in https will become wss for secure web sockets
-        this.ws_host = location.protocol.replace('http', 'ws') + "//" + location.host;
         this.kernel_url = utils.url_path_join(this.kernel_service_url, this.kernel_id);
         this.start_channels();
     };
@@ -145,16 +148,16 b' define(['
     Kernel.prototype.start_channels = function () {
         var that = this;
         this.stop_channels();
-        var ws_host_url = this.ws_host + this.kernel_url;
+        var ws_host_url = this.ws_url + this.kernel_url;
         console.log("Starting WebSockets:", ws_host_url);
         this.shell_channel = new this.WebSocket(
-            this.ws_host + utils.url_join_encode(this.kernel_url, "shell")
+            this.ws_url + utils.url_join_encode(this.kernel_url, "shell")
         );
         this.stdin_channel = new this.WebSocket(
-            this.ws_host + utils.url_join_encode(this.kernel_url, "stdin")
+            this.ws_url + utils.url_join_encode(this.kernel_url, "stdin")
         );
         this.iopub_channel = new this.WebSocket(
-            this.ws_host + utils.url_join_encode(this.kernel_url, "iopub")
+            this.ws_url + utils.url_join_encode(this.kernel_url, "iopub")
         );
         
         var already_called_onclose = false; // only alert once

IPython/html/templates/notebook.html

@@ -24,6 +24,7 b' window.mathjax_url = "{{mathjax_url}}";'
 
 data-project="{{project}}"
 data-base-url="{{base_url}}"
+data-ws-url="{{ws_url}}"
 data-notebook-name="{{notebook_name}}"
 data-notebook-path="{{notebook_path}}"
 class="notebook_app"