docs: Add guide on how to simulate real apps in ndnSIM

Change-Id: I3694a8791b9540fc1b926a83ff55421b47e0f2a2
diff --git a/examples/ndn-cxx-simple/real-app-starter.hpp b/examples/ndn-cxx-simple/real-app-starter.hpp
new file mode 100644
index 0000000..00119e5
--- /dev/null
+++ b/examples/ndn-cxx-simple/real-app-starter.hpp
@@ -0,0 +1,67 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2011-2015  Regents of the University of California.
+ *
+ * This file is part of ndnSIM. See AUTHORS for complete list of ndnSIM authors and
+ * contributors.
+ *
+ * ndnSIM is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * ndnSIM is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ * PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * ndnSIM, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+#ifndef NDNSIM_EXAMPLES_NDN_CXX_SIMPLE_REAL_APP_STARTER_HPP
+#define NDNSIM_EXAMPLES_NDN_CXX_SIMPLE_REAL_APP_STARTER_HPP
+
+#include "real-app.hpp"
+
+#include "ns3/ndnSIM/helper/ndn-stack-helper.hpp"
+#include "ns3/application.h"
+
+namespace ns3 {
+
+// Class inheriting from ns3::Application
+class RealAppStarter : public Application
+{
+public:
+  static TypeId
+  GetTypeId()
+  {
+    static TypeId tid = TypeId("RealAppStarter")
+      .SetParent<Application>()
+      .AddConstructor<RealAppStarter>();
+
+    return tid;
+  }
+
+protected:
+  // inherited from Application base class.
+  virtual void
+  StartApplication()
+  {
+    // Create an instance of the app, and passing the dummy version of KeyChain (no real signing)
+    m_instance.reset(new app::RealApp(ndn::StackHelper::getKeyChain()));
+    m_instance->run(); // can be omitted
+  }
+
+  virtual void
+  StopApplication()
+  {
+    // Stop and destroy the instance of the app
+    m_instance.reset();
+  }
+
+private:
+  std::unique_ptr<app::RealApp> m_instance;
+};
+
+} // namespace ns3
+
+#endif // NDNSIM_EXAMPLES_NDN_CXX_SIMPLE_REAL_APP_STARTER_HPP