diff --git a/web/gui/src/main/webapp/app/view/topo2/topo2Event.js b/web/gui/src/main/webapp/app/view/topo2/topo2Event.js
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+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ ONOS GUI -- Topology Event Module.
+
+ Defines the conduit between the client and the server:
+ - provides a clean API for sending events to the server
+ - dispatches incoming events from the server to the appropriate sub-module
+
+ */
+
+(function () {
+    'use strict';
+
+    // injected refs
+    var $log, wss, t2fs;
+
+    // internal state
+    var handlerMap,
+        openListener;
+
+    // TODO: only add heartbeat timer etc. if we really need to be doing that..
+
+    // ========================== Helper Functions
+
+    function createHandlerMap() {
+        handlerMap = {
+            topo2AllInstances: t2fs,
+            topo2CurrentLayout: t2fs,
+            topo2CurrentRegion: t2fs,
+            topo2StartDone: t2fs
+
+            // Add further event names / module references as needed
+        };
+    }
+
+    function wsOpen(host, url) {
+        $log.debug('topo2Event: WSopen - cluster node:', host, 'URL:', url);
+        // tell the server we are ready to receive topo events
+        wss.sendEvent('topo2Start');
+    }
+
+    // bind our event handlers to the web socket service, so that our
+    //  callbacks get invoked for incoming events
+    function bindHandlers() {
+        wss.bindHandlers(handlerMap);
+        $log.debug('topo2 event handlers bound');
+    }
+
+    // tell the server we are ready to receive topology events
+    function start() {
+        // in case we fail over to a new server,
+        // listen for wsock-open events
+        openListener = wss.addOpenListener(wsOpen);
+        wss.sendEvent('topo2Start');
+        $log.debug('topo2 comms started');
+    }
+
+    // tell the server we no longer wish to receive topology events
+    function stop() {
+        wss.sendEvent('topo2Stop');
+        wss.unbindHandlers(handlerMap);
+        wss.removeOpenListener(openListener);
+        openListener = null;
+        $log.debug('topo2 comms stopped');
+    }
+
+    // ========================== Main Service Definition
+
+    angular.module('ovTopo2')
+    .factory('Topo2EventService',
+        ['$log', 'WebSocketService', 'Topo2ForceService',
+
+        function (_$log_, _wss_, _t2fs_) {
+            $log = _$log_;
+            wss = _wss_;
+            t2fs = _t2fs_;
+
+            // deferred creation of handler map, so module references are good
+            createHandlerMap();
+
+            return {
+                bindHandlers: bindHandlers,
+                start: start,
+                stop: stop
+            };
+        }]);
+}());