diff --git a/networktransport.cpp b/networktransport.cpp
index 8f1b633..9250643 100644
--- a/networktransport.cpp
+++ b/networktransport.cpp
@@ -13,7 +13,8 @@ Transport<MyState, RemoteState>::Transport( MyState &initial_state, RemoteState
     current_state( initial_state ),
     sent_states( 1, TimestampedState<MyState>( timestamp(), 0, initial_state ) ),
     assumed_receiver_state( sent_states.begin() ),
-    received_states( 1, TimestampedState<RemoteState>( timestamp(), 0, initial_remote ) )
+    received_states( 1, TimestampedState<RemoteState>( timestamp(), 0, initial_remote ) ),
+    last_receiver_state( initial_remote )
 {
   /* server */
 }
@@ -26,7 +27,8 @@ Transport<MyState, RemoteState>::Transport( MyState &initial_state, RemoteState
     current_state( initial_state ),
     sent_states( 1, TimestampedState<MyState>( timestamp(), 0, initial_state ) ),
     assumed_receiver_state( sent_states.begin() ),
-    received_states( 1, TimestampedState<RemoteState>( timestamp(), 0, initial_remote ) )
+    received_states( 1, TimestampedState<RemoteState>( timestamp(), 0, initial_remote ) ),
+    last_receiver_state( initial_remote )
 {
   /* client */
 }
@@ -144,7 +146,6 @@ void Transport<MyState, RemoteState>::send_to_receiver( void )
     }
 
     /* send instruction */
-    /* XXX what about MTU problem? */
     string s = inst.tostring();
 
     try {
@@ -225,6 +226,10 @@ void Transport<MyState, RemoteState>::recv( void )
 
   if ( !found ) {
     //    fprintf( stderr, "Ignoring out-of-order packet. Reference state %d has been discarded or hasn't yet been received.\n", int(inst.old_num) );
+    /* There may be some benefit to storing these diffs until they can be used later,
+       but my guess is that the benefit is slim -- the diffs are likely to be small enough
+       that the entire diff will usually fit in one datagram, and by the time of retransmission
+       the target state will be different anyway. */
     return;
   }
 
@@ -282,3 +287,25 @@ void Transport<MyState, RemoteState>::process_throwaway_until( uint64_t throwawa
 
   assert( received_states.size() > 0 );
 }
+
+template <class MyState, class RemoteState>
+string Transport<MyState, RemoteState>::get_remote_diff( void )
+{
+  /* find diff between last receiver state and current remote state, then rationalize states */
+
+  string ret( received_states.back().state.diff_from( last_receiver_state, 1 ) );
+
+  last_receiver_state = received_states.back().state;
+
+  MyState * const oldest_receiver_state = &received_states.front().state;
+
+  last_receiver_state.subtract( oldest_receiver_state );
+
+  for ( typename list< TimestampedState<RemoteState> >::reverse_iterator i = received_states.rbegin();
+	i != received_states.rend();
+	i++ ) {
+    i->state.subtract( oldest_receiver_state );
+  }  
+
+  return ret;
+}
diff --git a/networktransport.hpp b/networktransport.hpp
index ca5bcb2..28a1244 100644
--- a/networktransport.hpp
+++ b/networktransport.hpp
@@ -76,21 +76,27 @@ namespace Network {
 
     /* simple receiver */
     list< TimestampedState<RemoteState> > received_states;
+    MyState last_receiver_state; /* the state we were in when user last queried state */
 
   public:
     Transport( MyState &initial_state, RemoteState &initial_remote );
     Transport( MyState &initial_state, RemoteState &initial_remote,
 	       const char *key_str, const char *ip, int port );
 
+    /* Send data or an ack if necessary.
+       Returns the number of ms to wait until next event. */
     int tick( void );
 
+    /* Blocks waiting for a packet. */
     void recv( void );
 
     int port( void ) { return connection.port(); }
     string get_key( void ) { return connection.get_key(); }
 
     MyState &get_current_state( void ) { return current_state; }
-    RemoteState &get_remote_state( void ) { return received_states.back().state; }
+
+    string get_remote_diff( void );
+
     uint64_t get_remote_state_num( void ) { return received_states.back().num; }
 
     int fd( void ) { return connection.fd(); }
diff --git a/ntester.cpp b/ntester.cpp
index 9c1711d..80b72a4 100644
--- a/ntester.cpp
+++ b/ntester.cpp
@@ -52,12 +52,7 @@ int main( int argc, char *argv[] )
 	  n->recv();
 
 	  if ( n->get_remote_state_num() != last_num ) {
-	    fprintf( stderr, "Num: %d. Contents: ",
-		     (int)n->get_remote_state_num() );
-	    for ( size_t i = 0; i < n->get_remote_state().user_bytes.size(); i++ ) {
-	      fprintf( stderr, "%c", n->get_remote_state().user_bytes[ i ] );
-	    }
-	    fprintf( stderr, "\n" );
+	    fprintf( stderr, "%s\n", n->get_remote_diff().c_str() );
 	    last_num = n->get_remote_state_num();
 	  }
 	}