diff --git a/xwords4/common/comtypes.h b/xwords4/common/comtypes.h
index b36d99994..42130e2ae 100644
--- a/xwords4/common/comtypes.h
+++ b/xwords4/common/comtypes.h
@@ -47,6 +47,7 @@
 #endif
 #define MAX_COLS MAX_ROWS
 
+#define STREAM_VERS_DUPLICATE 0x1B
 #define STREAM_VERS_DISABLEDS 0x1A
 #define STREAM_VERS_DEVIDS 0x19
 #define STREAM_VERS_MULTIADDR 0x18
@@ -88,7 +89,7 @@
 #define STREAM_VERS_405  0x01
 
 /* search for FIX_NEXT_VERSION_CHANGE next time this is changed */
-#define CUR_STREAM_VERS STREAM_VERS_DISABLEDS
+#define CUR_STREAM_VERS STREAM_VERS_DUPLICATE
 
 typedef struct XP_Rect {
     XP_S16 left;
diff --git a/xwords4/common/game.c b/xwords4/common/game.c
index 1facc227f..187a6e1c7 100644
--- a/xwords4/common/game.c
+++ b/xwords4/common/game.c
@@ -487,7 +487,9 @@ gi_copy( MPFORMAL CurGameInfo* destGI, const CurGameInfo* srcGI )
     destGI->phoniesAction = srcGI->phoniesAction;
     destGI->allowPickTiles = srcGI->allowPickTiles;
     destGI->forceChannel = srcGI->forceChannel;
-    XP_LOGF( "%s: copied forceChannel: %d", __func__, destGI->forceChannel );
+    destGI->inDuplicateMode = srcGI->inDuplicateMode;
+    XP_LOGF( "%s: copied forceChannel: %d; inDuplicateMode: %d", __func__,
+             destGI->forceChannel, destGI->inDuplicateMode );
 
     for ( srcPl = srcGI->players, destPl = destGI->players, ii = 0; 
           ii < nPlayers; ++srcPl, ++destPl, ++ii ) {
@@ -566,6 +568,9 @@ gi_readFromStream( MPFORMAL XWStreamCtxt* stream, CurGameInfo* gi )
     gi->phoniesAction = (XWPhoniesChoice)stream_getBits( stream, 2 );
     gi->timerEnabled = stream_getBits( stream, 1 );
 
+    gi->inDuplicateMode = strVersion >= STREAM_VERS_DUPLICATE
+        ? stream_getBits( stream, 1 )
+        : XP_FALSE;
     if ( strVersion >= STREAM_VERS_41B4 ) {
         gi->allowPickTiles = stream_getBits( stream, 1 );
         gi->allowHintRect = stream_getBits( stream, 1 );
@@ -641,6 +646,7 @@ gi_writeToStream( XWStreamCtxt* stream, const CurGameInfo* gi )
     stream_putBits( stream, 1, gi->hintsNotAllowed );
     stream_putBits( stream, 2, gi->phoniesAction );
     stream_putBits( stream, 1, gi->timerEnabled );
+    stream_putBits( stream, 1, gi->inDuplicateMode );
     stream_putBits( stream, 1, gi->allowPickTiles );
     stream_putBits( stream, 1, gi->allowHintRect );
     stream_putBits( stream, 1, gi->confirmBTConnect );
diff --git a/xwords4/common/gameinfo.h b/xwords4/common/gameinfo.h
index aa931bc5b..608b7c059 100644
--- a/xwords4/common/gameinfo.h
+++ b/xwords4/common/gameinfo.h
@@ -58,6 +58,7 @@ typedef struct CurGameInfo {
     XP_Bool timerEnabled;
     XP_Bool allowPickTiles;
     XP_Bool allowHintRect;
+    XP_Bool inDuplicateMode;
     XWPhoniesChoice phoniesAction;
     XP_Bool confirmBTConnect;   /* only used for BT */
 } CurGameInfo;
diff --git a/xwords4/common/server.c b/xwords4/common/server.c
index 325f3b38a..85d5404dd 100644
--- a/xwords4/common/server.c
+++ b/xwords4/common/server.c
@@ -1,6 +1,6 @@
 /* -*- compile-command: "cd ../linux && make -j3 MEMDEBUG=TRUE"; -*- */
 /* 
- * Copyright 1997-2009 by Eric House (xwords@eehouse.org).  All rights
+ * Copyright 1997 - 2019 by Eric House (xwords@eehouse.org).  All rights
  * reserved.
  *
  * This program is free software; you can redistribute it and/or
@@ -84,6 +84,7 @@ typedef struct ServerVolatiles {
 
 typedef struct ServerNonvolatiles {
     XP_U32 lastMoveTime;    /* seconds of last turn change */
+    XP_S32 dupTimerExpires;
     XP_U8 nDevices;
     XW_State gameState;
     XW_State stateAfterShow;
@@ -103,6 +104,9 @@ typedef struct ServerNonvolatiles {
     RemoteAddress addresses[MAX_NUM_PLAYERS];
     XWStreamCtxt* prevMoveStream;     /* save it to print later */
     XWStreamCtxt* prevWordsStream;
+    XP_Bool dupTurnsMade[MAX_NUM_PLAYERS];
+    XP_Bool dupTurnsForced[MAX_NUM_PLAYERS];
+    XP_Bool dupTurnsSent;       /* used on client only */
 } ServerNonvolatiles;
 
 struct ServerCtxt {
@@ -290,6 +294,9 @@ getNV( XWStreamCtxt* stream, ServerNonvolatiles* nv, XP_U16 nPlayers )
     if ( STREAM_VERS_DICTNAME <= version ) {
         nv->lastMoveTime = stream_getU32( stream );
     }
+    if ( STREAM_VERS_DUPLICATE <= version ) {
+        nv->dupTimerExpires = stream_getU32( stream );
+    }
 
     if ( version < STREAM_VERS_SERVER_SAVES_TOSHOW ) {
         /* no longer used */
@@ -327,6 +334,15 @@ getNV( XWStreamCtxt* stream, ServerNonvolatiles* nv, XP_U16 nPlayers )
     }
     /* XP_LOGF( "%s: read streamVersion: 0x%x", __func__, nv->streamVersion ); */
 #endif
+
+    if ( version >= STREAM_VERS_DUPLICATE ) {
+        for ( ii = 0; ii < nPlayers; ++ii ) {
+            nv->dupTurnsMade[ii] = stream_getBits( stream, 1 );
+            XP_LOGF( "%s(): dupTurnsMade[%d]: %d", __func__, ii, nv->dupTurnsMade[ii] );
+            nv->dupTurnsForced[ii] = stream_getBits( stream, 1 );
+        }
+        nv->dupTurnsSent = stream_getBits( stream, 1 );
+    }
 } /* getNV */
 
 static void
@@ -335,6 +351,7 @@ putNV( XWStreamCtxt* stream, const ServerNonvolatiles* nv, XP_U16 nPlayers )
     XP_U16 ii;
 
     stream_putU32( stream, nv->lastMoveTime );
+    stream_putU32( stream, nv->dupTimerExpires );
 
     /* number of players is upper limit on device count */
     stream_putBits( stream, NDEVICES_NBITS, nv->nDevices-1 );
@@ -358,6 +375,12 @@ putNV( XWStreamCtxt* stream, const ServerNonvolatiles* nv, XP_U16 nPlayers )
     stream_putU8( stream, nv->streamVersion );
     /* XP_LOGF( "%s: wrote streamVersion: 0x%x", __func__, nv->streamVersion ); */
 #endif
+
+    for ( ii = 0; ii < nPlayers; ++ii ) {
+        stream_putBits( stream, 1, nv->dupTurnsMade[ii] );
+        stream_putBits( stream, 1, nv->dupTurnsForced[ii] );
+    }
+    stream_putBits( stream, 1, nv->dupTurnsSent );
 } /* putNV */
 
 static XWStreamCtxt*