diff --git a/src/ccnx/sync-socket.h b/src/ccnx/sync-socket.h
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+++ b/src/ccnx/sync-socket.h
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+/* -*- Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil -*- */
+/*
+ * Copyright (c) 2012 University of California, Los Angeles
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation;
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * Author: Yingdi Yu <yingdi@cs.ucla.edu>
+ */
+
+#ifndef SYNC_SOCKET_H
+#define SYNC_SOCKET_H
+
+#include "sync-logic.h"
+#include <boost/function.hpp>
+#include <boost/unordered_map.hpp>
+#include "sync-seq-no.h"
+#include <ndn.cxx/wrapper/wrapper.h>
+#include <utility>
+#include <map>
+#include <vector>
+#include <sstream>
+
+namespace Sync {
+
+/**
+ * \ingroup sync
+ * @brief A simple interface to interact with client code
+ */
+class SyncSocket
+{
+public:
+  typedef boost::function< void (const std::vector<MissingDataInfo> &, SyncSocket * ) > NewDataCallback;
+  typedef boost::function< void ( const std::string &/*prefix*/ ) > RemoveCallback;
+  /**
+   * @brief the constructor for SyncAppSocket; the parameter syncPrefix
+   * should be passed to the constructor of m_syncAppWrapper; the other
+   * parameter should be passed to the constructor of m_fetcher; furthermore,
+   * the fetch function of m_fetcher should be a second paramter passed to
+   * the constructor of m_syncAppWrapper, so that m_syncAppWrapper can tell
+   * m_fetcher to fetch the actual app data after it learns the names
+   *
+   * @param syncPrefix the name prefix for Sync Interest
+   * @param dataCallback the callback to process data
+   */
+  SyncSocket (const std::string &syncPrefix, 
+              ndn::Ptr<SyncPolicyManager> syncPolicyManager,
+              NewDataCallback dataCallback, 
+              RemoveCallback rmCallback);
+
+  ~SyncSocket ();
+
+  bool 
+  publishData(const std::string &prefix, uint32_t session, const char *buf, size_t len, int freshness);
+
+  void 
+  remove (const std::string &prefix) 
+  { m_syncLogic.remove(prefix); }
+
+  void 
+  fetchData(const std::string &prefix, const SeqNo &seq, const ndn::DataCallback& callback, int retry = 0);
+
+  std::string 
+  getRootDigest() 
+  { return m_syncLogic.getRootDigest(); }
+
+  uint32_t
+  getNextSeq (const std::string &prefix, uint32_t session);
+
+  SyncLogic &
+  getLogic () 
+  { return m_syncLogic; }
+
+  // make this a static function so we don't have to create socket instance without
+  // knowing the local prefix. it's a wrong place for this function anyway
+  static std::string
+  GetLocalPrefix (); 
+  
+private:
+  void 
+  passCallback(const std::vector<MissingDataInfo> &v) 
+  { m_newDataCallback(v, this); }
+
+  void
+  onChatDataTimeout(ndn::Ptr<ndn::Closure> closure, ndn::Ptr<ndn::Interest> interest, int retry);
+
+  void
+  onChatDataUnverified(ndn::Ptr<ndn::Data> data);
+
+private:
+  typedef boost::unordered_map<std::string, SeqNo> SequenceLog;
+  NewDataCallback m_newDataCallback;
+  SequenceLog m_sequenceLog;
+  ndn::Ptr<SyncPolicyManager> m_syncPolicyManager;
+  ndn::Ptr<ndn::Wrapper> m_handler;
+  SyncLogic      m_syncLogic;
+};
+
+} // Sync
+
+#endif // SYNC_SOCKET_H