diff --git a/tools/ndngetfile.cpp b/tools/ndngetfile.cpp
index 99f54ca..1f59a36 100644
--- a/tools/ndngetfile.cpp
+++ b/tools/ndngetfile.cpp
@@ -1,6 +1,6 @@
-/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014,  Regents of the University of California.
+ * Copyright (c) 2014-2017, Regents of the University of California.
  *
  * This file is part of NDN repo-ng (Next generation of NDN repository).
  * See AUTHORS.md for complete list of repo-ng authors and contributors.
@@ -55,6 +55,7 @@
                          bind(&Consumer::onVersionedData, this, _1, _2)
                          :
                          bind(&Consumer::onUnversionedData, this, _1, _2),
+                         bind(&Consumer::onTimeout, this, _1), // Nack
                          bind(&Consumer::onTimeout, this, _1));
 }
 
@@ -72,7 +73,7 @@
 }
 
 void
-Consumer::onVersionedData(const Interest& interest, Data& data)
+Consumer::onVersionedData(const Interest& interest, const Data& data)
 {
   const Name& name = data.getName();
 
@@ -110,7 +111,7 @@
 }
 
 void
-Consumer::onUnversionedData(const Interest& interest, Data& data)
+Consumer::onUnversionedData(const Interest& interest, const Data& data)
 {
   const Name& name = data.getName();
   //std::cout<<"recevied data name = "<<name<<std::endl;
@@ -248,7 +249,7 @@
           {
             interestLifetime = boost::lexical_cast<int>(optarg);
           }
-        catch (boost::bad_lexical_cast&)
+        catch (const boost::bad_lexical_cast&)
           {
             std::cerr << "ERROR: -l option should be an integer." << std::endl;
             return 1;
@@ -260,7 +261,7 @@
           {
             timeout = boost::lexical_cast<int>(optarg);
           }
-        catch (boost::bad_lexical_cast&)
+        catch (const boost::bad_lexical_cast&)
           {
             std::cerr << "ERROR: -w option should be an integer." << std::endl;
             return 1;
diff --git a/tools/ndngetfile.hpp b/tools/ndngetfile.hpp
index 8e84440..e7e851b 100644
--- a/tools/ndngetfile.hpp
+++ b/tools/ndngetfile.hpp
@@ -1,6 +1,6 @@
-/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014,  Regents of the University of California.
+ * Copyright (c) 2014-2017, Regents of the University of California.
  *
  * This file is part of NDN repo-ng (Next generation of NDN repository).
  * See AUTHORS.md for complete list of repo-ng authors and contributors.
@@ -55,14 +55,14 @@
   fetchData(const ndn::Name& name);
 
   void
-  onVersionedData(const ndn::Interest& interest, ndn::Data& data);
+  onVersionedData(const ndn::Interest& interest, const ndn::Data& data);
 
   void
-  onUnversionedData(const ndn::Interest& interest, ndn::Data& data);
+  onUnversionedData(const ndn::Interest& interest, const ndn::Data& data);
 
   void
   onTimeout(const ndn::Interest& interest);
-  
+
   void
   readData(const ndn::Data& data);
 
diff --git a/tools/ndnputfile.cpp b/tools/ndnputfile.cpp
index 7dd92e5..f08a7a3 100644
--- a/tools/ndnputfile.cpp
+++ b/tools/ndnputfile.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014-2016,  Regents of the University of California.
+ * Copyright (c) 2014-2017, Regents of the University of California.
  *
  * This file is part of NDN repo-ng (Next generation of NDN repository).
  * See AUTHORS.md for complete list of repo-ng authors and contributors.
@@ -14,7 +14,7 @@
  * PURPOSE.  See the GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License along with
- * repo-ng, e.g., in COPYING.md file.  if (not, see <http://www.gnu.org/licenses/>.
+ * repo-ng, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include "../src/repo-command-parameter.hpp"
@@ -50,7 +50,7 @@
 static const uint64_t DEFAULT_CHECK_PERIOD = 1000;
 static const size_t PRE_SIGN_DATA_COUNT = 11;
 
-class NdnPutFile : ndn::noncopyable
+class NdnPutFile : boost::noncopyable
 {
 public:
   class Error : public std::runtime_error
@@ -93,7 +93,7 @@
   startInsertCommand();
 
   void
-  onInsertCommandResponse(const ndn::Interest& interest, ndn::Data& data);
+  onInsertCommandResponse(const ndn::Interest& interest, const ndn::Data& data);
 
   void
   onInsertCommandTimeout(const ndn::Interest& interest);
@@ -120,7 +120,7 @@
   startCheckCommand();
 
   void
-  onCheckCommandResponse(const ndn::Interest& interest, ndn::Data& data);
+  onCheckCommandResponse(const ndn::Interest& interest, const ndn::Data& data);
 
   void
   onCheckCommandTimeout(const ndn::Interest& interest);
@@ -186,7 +186,7 @@
       boost::iostreams::read(*insertStream, reinterpret_cast<char*>(buffer), DEFAULT_BLOCK_SIZE);
 
     if (readSize <= 0) {
-      throw Error("Error reading from the input stream");
+      BOOST_THROW_EXCEPTION(Error("Error reading from the input stream"));
     }
 
     shared_ptr<ndn::Data> data =
@@ -250,17 +250,18 @@
   ndn::Interest commandInterest = generateCommandInterest(repoPrefix, "insert", parameters);
   m_face.expressInterest(commandInterest,
                          bind(&NdnPutFile::onInsertCommandResponse, this, _1, _2),
+                         bind(&NdnPutFile::onInsertCommandTimeout, this, _1), // Nack
                          bind(&NdnPutFile::onInsertCommandTimeout, this, _1));
 }
 
 void
-NdnPutFile::onInsertCommandResponse(const ndn::Interest& interest, ndn::Data& data)
+NdnPutFile::onInsertCommandResponse(const ndn::Interest& interest, const ndn::Data& data)
 {
   RepoCommandResponse response(data.getContent().blockFromValue());
   int statusCode = response.getStatusCode();
   if (statusCode >= 400) {
-    throw Error("insert command failed with code " +
-                boost::lexical_cast<std::string>(statusCode));
+    BOOST_THROW_EXCEPTION(Error("insert command failed with code " +
+                                boost::lexical_cast<std::string>(statusCode)));
   }
   m_processId = response.getProcessId();
 
@@ -271,7 +272,7 @@
 void
 NdnPutFile::onInsertCommandTimeout(const ndn::Interest& interest)
 {
-  throw Error("command response timeout");
+  BOOST_THROW_EXCEPTION(Error("command response timeout"));
 }
 
 void
@@ -290,7 +291,7 @@
     ndn::Name::Component segmentComponent = interest.getName().get(prefix.size());
     segmentNo = segmentComponent.toSegment();
   }
-  catch (tlv::Error& e) {
+  catch (const tlv::Error& e) {
     if (isVerbose) {
       std::cerr << "Error processing incoming interest " << interest << ": "
                 << e.what() << std::endl;
@@ -333,11 +334,11 @@
     boost::iostreams::read(*insertStream, reinterpret_cast<char*>(buffer), DEFAULT_BLOCK_SIZE);
 
   if (readSize <= 0) {
-    throw Error("Error reading from the input stream");
+    BOOST_THROW_EXCEPTION(Error("Error reading from the input stream"));
   }
 
   if (insertStream->peek() != std::istream::traits_type::eof()) {
-    throw Error("Input data does not fit into one Data packet");
+    BOOST_THROW_EXCEPTION(Error("Input data does not fit into one Data packet"));
   }
 
   shared_ptr<ndn::Data> data = make_shared<ndn::Data>(m_dataPrefix);
@@ -352,7 +353,7 @@
 void
 NdnPutFile::onRegisterFailed(const ndn::Name& prefix, const std::string& reason)
 {
-  throw Error("onRegisterFailed: " + reason);
+  BOOST_THROW_EXCEPTION(Error("onRegisterFailed: " + reason));
 }
 
 void
@@ -386,17 +387,18 @@
                                                           .setProcessId(m_processId));
   m_face.expressInterest(checkInterest,
                          bind(&NdnPutFile::onCheckCommandResponse, this, _1, _2),
+                         bind(&NdnPutFile::onCheckCommandTimeout, this, _1), // Nack
                          bind(&NdnPutFile::onCheckCommandTimeout, this, _1));
 }
 
 void
-NdnPutFile::onCheckCommandResponse(const ndn::Interest& interest, ndn::Data& data)
+NdnPutFile::onCheckCommandResponse(const ndn::Interest& interest, const ndn::Data& data)
 {
   RepoCommandResponse response(data.getContent().blockFromValue());
   int statusCode = response.getStatusCode();
   if (statusCode >= 400) {
-    throw Error("Insert check command failed with code: " +
-                boost::lexical_cast<std::string>(statusCode));
+    BOOST_THROW_EXCEPTION(Error("Insert check command failed with code: " +
+                                boost::lexical_cast<std::string>(statusCode)));
   }
 
   if (m_isFinished) {
@@ -424,7 +426,7 @@
 void
 NdnPutFile::onCheckCommandTimeout(const ndn::Interest& interest)
 {
-  throw Error("check response timeout");
+  BOOST_THROW_EXCEPTION(Error("check response timeout"));
 }
 
 ndn::Interest
@@ -495,7 +497,7 @@
       try {
         ndnPutFile.freshnessPeriod = milliseconds(boost::lexical_cast<uint64_t>(optarg));
       }
-      catch (boost::bad_lexical_cast&) {
+      catch (const boost::bad_lexical_cast&) {
         std::cerr << "-x option should be an integer.";
         return 1;
       }
@@ -504,7 +506,7 @@
       try {
         ndnPutFile.interestLifetime = milliseconds(boost::lexical_cast<uint64_t>(optarg));
       }
-      catch (boost::bad_lexical_cast&) {
+      catch (const boost::bad_lexical_cast&) {
         std::cerr << "-l option should be an integer.";
         return 1;
       }
@@ -514,7 +516,7 @@
       try {
         ndnPutFile.timeout = milliseconds(boost::lexical_cast<uint64_t>(optarg));
       }
-      catch (boost::bad_lexical_cast&) {
+      catch (const boost::bad_lexical_cast&) {
         std::cerr << "-w option should be an integer.";
         return 1;
       }
@@ -567,7 +569,7 @@
   try {
     return repo::main(argc, argv);
   }
-  catch (std::exception& e) {
+  catch (const std::exception& e) {
     std::cerr << "ERROR: " << e.what() << std::endl;
     return 2;
   }
diff --git a/tools/ndnrepowatch.cpp b/tools/ndnrepowatch.cpp
index c5128f3..4172d79 100644
--- a/tools/ndnrepowatch.cpp
+++ b/tools/ndnrepowatch.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014,  Regents of the University of California.
+ * Copyright (c) 2014-2017, Regents of the University of California.
  *
  * This file is part of NDN repo-ng (Next generation of NDN repository).
  * See AUTHORS.md for complete list of repo-ng authors and contributors.
@@ -14,7 +14,7 @@
  * PURPOSE.  See the GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License along with
- * repo-ng, e.g., in COPYING.md file.  if (not, see <http://www.gnu.org/licenses/>.
+ * repo-ng, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include "../src/repo-command-parameter.hpp"
@@ -50,7 +50,7 @@
   STOP
 };
 
-class NdnRepoWatch : ndn::noncopyable
+class NdnRepoWatch : boost::noncopyable
 {
 public:
   class Error : public std::runtime_error
@@ -87,7 +87,7 @@
   startWatchCommand();
 
   void
-  onWatchCommandResponse(const ndn::Interest& interest, ndn::Data& data);
+  onWatchCommandResponse(const ndn::Interest& interest, const ndn::Data& data);
 
   void
   onWatchCommandTimeout(const ndn::Interest& interest);
@@ -168,6 +168,7 @@
     m_face.expressInterest(commandInterest,
                            bind(&NdnRepoWatch::onWatchCommandResponse, this,
                                      _1, _2),
+                           bind(&NdnRepoWatch::onWatchCommandTimeout, this, _1), // Nack
                            bind(&NdnRepoWatch::onWatchCommandTimeout, this, _1));
   }
   else if (status == STOP){
@@ -175,6 +176,7 @@
     m_face.expressInterest(commandInterest,
                            bind(&NdnRepoWatch::onWatchCommandResponse, this,
                                      _1, _2),
+                           bind(&NdnRepoWatch::onWatchCommandTimeout, this, _1), // Nack
                            bind(&NdnRepoWatch::onWatchCommandTimeout, this, _1));
   }
   else if (status == CHECK){
@@ -182,19 +184,20 @@
     m_face.expressInterest(commandInterest,
                            bind(&NdnRepoWatch::onWatchCommandResponse, this,
                                      _1, _2),
+                           bind(&NdnRepoWatch::onWatchCommandTimeout, this, _1), // Nack
                            bind(&NdnRepoWatch::onWatchCommandTimeout, this, _1));
   }
 
 }
 
 void
-NdnRepoWatch::onWatchCommandResponse(const ndn::Interest& interest, ndn::Data& data)
+NdnRepoWatch::onWatchCommandResponse(const ndn::Interest& interest, const ndn::Data& data)
 {
   RepoCommandResponse response(data.getContent().blockFromValue());
   int statusCode = response.getStatusCode();
   if (statusCode >= 400) {
-    throw Error("Watch command failed with code " +
-                boost::lexical_cast<std::string>(statusCode));
+    BOOST_THROW_EXCEPTION(Error("Watch command failed with code " +
+                                boost::lexical_cast<std::string>(statusCode)));
   }
   else if (statusCode == 101) {
     std::cerr << "Watching prefix is stopped!" <<std::endl;
@@ -214,15 +217,15 @@
     return;
   }
   else {
-    throw Error("Unrecognized Status Code " +
-                boost::lexical_cast<std::string>(statusCode));
+    BOOST_THROW_EXCEPTION(Error("Unrecognized Status Code " +
+                                boost::lexical_cast<std::string>(statusCode)));
   }
 }
 
 void
 NdnRepoWatch::onWatchCommandTimeout(const ndn::Interest& interest)
 {
-  throw Error("command response timeout");
+  BOOST_THROW_EXCEPTION(Error("command response timeout"));
 }
 
 void
@@ -240,13 +243,14 @@
                                                           .setName(m_dataPrefix));
   m_face.expressInterest(checkInterest,
                          bind(&NdnRepoWatch::onWatchCommandResponse, this, _1, _2),
+                         bind(&NdnRepoWatch::onCheckCommandTimeout, this, _1), // Nack
                          bind(&NdnRepoWatch::onCheckCommandTimeout, this, _1));
 }
 
 void
 NdnRepoWatch::onCheckCommandTimeout(const ndn::Interest& interest)
 {
-  throw Error("check response timeout");
+  BOOST_THROW_EXCEPTION(Error("check response timeout"));
 }
 
 void
@@ -255,8 +259,8 @@
   RepoCommandResponse response(data.getContent().blockFromValue());
   int statusCode = response.getStatusCode();
   if (statusCode != 101) {
-    throw Error("Watch stop command failed with code: " +
-                boost::lexical_cast<std::string>(statusCode));
+    BOOST_THROW_EXCEPTION(Error("Watch stop command failed with code: " +
+                                boost::lexical_cast<std::string>(statusCode)));
   }
   else {
     std::cerr << "Status code is 101. Watching prefix is stopped successfully!" << std::endl;
@@ -268,7 +272,7 @@
 void
 NdnRepoWatch::onStopCommandTimeout(const ndn::Interest& interest)
 {
-  throw Error("stop response timeout");
+  BOOST_THROW_EXCEPTION(Error("stop response timeout"));
 }
 
 ndn::Interest
@@ -322,7 +326,7 @@
       try {
         app.freshnessPeriod = milliseconds(boost::lexical_cast<uint64_t>(optarg));
       }
-      catch (boost::bad_lexical_cast&) {
+      catch (const boost::bad_lexical_cast&) {
         std::cerr << "-x option should be an integer.";
         return 1;
       }
@@ -331,7 +335,7 @@
       try {
         app.interestLifetime = milliseconds(boost::lexical_cast<uint64_t>(optarg));
       }
-      catch (boost::bad_lexical_cast&) {
+      catch (const boost::bad_lexical_cast&) {
         std::cerr << "-l option should be an integer.";
         return 1;
       }
@@ -341,7 +345,7 @@
       try {
         app.watchTimeout = milliseconds(boost::lexical_cast<int64_t>(optarg));
       }
-      catch (boost::bad_lexical_cast&) {
+      catch (const boost::bad_lexical_cast&) {
         std::cerr << "-w option should be an integer.";
         return 1;
       }
@@ -351,7 +355,7 @@
       try {
         app.maxInterestNum = boost::lexical_cast<int64_t>(optarg);
       }
-      catch (boost::bad_lexical_cast&) {
+      catch (const boost::bad_lexical_cast&) {
         std::cerr << "-n option should be an integer.";
         return 1;
       }
@@ -398,7 +402,7 @@
   try {
     return repo::main(argc, argv);
   }
-  catch (std::exception& e) {
+  catch (const std::exception& e) {
     std::cerr << "ERROR: " << e.what() << std::endl;
     return 2;
   }
diff --git a/tools/repo-ng-ls.cpp b/tools/repo-ng-ls.cpp
index 862f133..3a916a3 100644
--- a/tools/repo-ng-ls.cpp
+++ b/tools/repo-ng-ls.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014,  Regents of the University of California.
+ * Copyright (c) 2014-2017, Regents of the University of California.
  *
  * This file is part of NDN repo-ng (Next generation of NDN repository).
  * See AUTHORS.md for complete list of repo-ng authors and contributors.
@@ -14,7 +14,7 @@
  * PURPOSE.  See the GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License along with
- * repo-ng, e.g., in COPYING.md file.  if (not, see <http://www.gnu.org/licenses/>.
+ * repo-ng, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include "../src/common.hpp"
@@ -88,7 +88,7 @@
    #endif
                           );
   if (rc != SQLITE_OK) {
-    throw Error("Database file open failure");
+    BOOST_THROW_EXCEPTION(Error("Database file open failure"));
   }
   sqlite3_exec(m_db, "PRAGMA synchronous = OFF", 0, 0, &errMsg);
   sqlite3_exec(m_db, "PRAGMA journal_mode = WAL", 0, 0, &errMsg);
@@ -98,20 +98,20 @@
 RepoEnumerator::readConfig(const std::string& configFile)
 {
   if (configFile.empty()) {
-    throw Error("Invalid configuration file name");
+    BOOST_THROW_EXCEPTION(Error("Invalid configuration file name"));
   }
 
   std::ifstream fin(configFile.c_str());
   if (!fin.is_open())
-    throw Error("failed to open configuration file '" + configFile + "'");
+    BOOST_THROW_EXCEPTION(Error("failed to open configuration file '" + configFile + "'"));
 
   using namespace boost::property_tree;
   ptree propertyTree;
   try {
     read_info(fin, propertyTree);
   }
-  catch (ptree_error& e) {
-    throw Error("failed to read configuration file '" + configFile + "'");
+  catch (const ptree_error& e) {
+    BOOST_THROW_EXCEPTION(Error("failed to read configuration file '" + configFile + "'"));
   }
   ptree repoConf = propertyTree.get_child("repo");
   m_dbPath = repoConf.get<std::string>("storage.path");
@@ -126,7 +126,7 @@
   string sql = string("SELECT id, name, keylocatorHash FROM NDN_REPO;");
   rc = sqlite3_prepare_v2(m_db, sql.c_str(), -1, &m_stmt, 0);
   if (rc != SQLITE_OK)
-    throw Error("Initiation Read Entries from Database Prepare error");
+    BOOST_THROW_EXCEPTION(Error("Initiation Read Entries from Database Prepare error"));
   uint64_t entryNumber = 0;
   while (true) {
     rc = sqlite3_step(m_stmt);
@@ -154,7 +154,7 @@
     }
     else {
       sqlite3_finalize(m_stmt);
-      throw Error("Initiation Read Entries error");
+      BOOST_THROW_EXCEPTION(Error("Initiation Read Entries error"));
     }
   }
   return entryNumber;
@@ -197,7 +197,7 @@
   try {
     return repo::main(argc, argv);
   }
-  catch (std::exception& e) {
+  catch (const std::exception& e) {
     std::cerr << "ERROR: " << e.what() << std::endl;
     return 2;
   }