diff --git a/1instance.c b/1instance.c
index 580b9cd..78d6b27 100644
--- a/1instance.c
+++ b/1instance.c
@@ -98,7 +98,9 @@ int loop_if_server(single_instance_struct* str,event_dispatcher dispatcher)
 
 void send_message(single_instance_struct* str,char* message)
 {
+#ifdef DEBUG_1INSTANCE
   int i=
+#endif
   write(str->fd,message,strlen(message));
 #ifdef DEBUG_1INSTANCE
   fprintf(stderr,"send: %s => %d(%d)\n",message,i,strlen(message));
diff --git a/Makefile b/Makefile
index 3ee328d..e9ad57b 100644
--- a/Makefile
+++ b/Makefile
@@ -11,7 +11,7 @@ FLAG24 = -DALLOW24BPP
 
 #OPTFLAGS=-g # -Wall
 OPTFLAGS=-O2 -Wall
-CFLAGS=$(OPTFLAGS) $(PTHREADDEF) $(FLAG24) $(INCLUDES)
+CFLAGS=$(OPTFLAGS) $(PTHREADDEF) $(FLAG24) $(INCLUDES) -DBACKCHANNEL
 RANLIB=ranlib
 
 LIBS=$(LDFLAGS) $(VNCSERVERLIB) $(PTHREADLIB)
diff --git a/cargs.c b/cargs.c
index dfb8f1c..6e41ae5 100644
--- a/cargs.c
+++ b/cargs.c
@@ -60,7 +60,7 @@ rfbProcessArguments(rfbScreenInfoPtr rfbScreen,int* argc, char *argv[])
 	    if (i + 1 >= *argc) rfbUsage();
 	    passwds[0] = argv[++i];
 	    passwds[1] = 0;
-	    rfbScreen->rfbAuthPasswdData = passwds;
+	    rfbScreen->rfbAuthPasswdData = (void*)passwds;
 	    rfbScreen->passwordCheck = rfbCheckPasswordByList;
         } else if (strcmp(argv[i], "-deferupdate") == 0) {  /* -desktop desktop-name */
             if (i + 1 >= *argc) rfbUsage();
diff --git a/mac.c b/mac.c
index b590e25..856bd20 100644
--- a/mac.c
+++ b/mac.c
@@ -327,6 +327,10 @@ refreshCallback(CGRectCount count, const CGRect *rectArray, void *ignore)
 	  break;
 	}
     }
+#ifdef BACKCHANNEL
+      else if(message[0]=='b')
+	rfbSendBackChannel(screen,message+1,strlen(message+1));
+#endif
   }
 #endif
 
@@ -377,6 +381,13 @@ int main(int argc,char *argv[])
       send_message(&single_instance,"l");
       exit(0);
     } else
+#ifdef BACKCHANNEL
+    if(i<argc-1 && !strcmp(argv[i],"-backchannel")) {
+      sprintf(message,"b%s",argv[i+1]);
+      send_message(&single_instance,message);
+      exit(0);
+    } else
+#endif
 #endif
     if(i<argc-1 && strcmp(argv[i],"-wait4client")==0) {
       maxSecsToConnect = atoi(argv[i+1])/1000;
diff --git a/rfb.h b/rfb.h
index fc7610a..a604dac 100644
--- a/rfb.h
+++ b/rfb.h
@@ -273,7 +273,7 @@ typedef struct
     FILE* httpFP;
 
     PasswordCheckProcPtr passwordCheck;
-    char* rfbAuthPasswdData;
+    void* rfbAuthPasswdData;
 
     /* this is the amount of milliseconds to wait at least before sending
      * an update. */
@@ -574,6 +574,10 @@ extern void rfbSendBell(rfbScreenInfoPtr rfbScreen);
 
 void rfbGotXCutText(rfbScreenInfoPtr rfbScreen, char *str, int len);
 
+#ifdef BACKCHANNEL
+extern void rfbSendBackChannel(rfbScreenInfoPtr s,char* message,int len);
+#endif
+
 /* translate.c */
 
 extern Bool rfbEconomicTranslate;
@@ -599,7 +603,6 @@ extern void httpCheckFds();
 
 /* auth.c */
 
-extern char *rfbAuthPasswdFile;
 extern void rfbAuthNewClient(rfbClientPtr cl);
 extern void rfbAuthProcessClientMessage(rfbClientPtr cl);
 
diff --git a/rfbproto.h b/rfbproto.h
index 2103c81..aa2f54b 100644
--- a/rfbproto.h
+++ b/rfbproto.h
@@ -268,7 +268,9 @@ typedef struct {
 #define rfbSetColourMapEntries 1
 #define rfbBell 2
 #define rfbServerCutText 3
-
+#ifdef BACKCHANNEL
+#define rfbBackChannel 15
+#endif
 
 /* client -> server */
 
@@ -297,6 +299,9 @@ typedef struct {
 #define rfbEncodingZlib 6
 #define rfbEncodingTight 7
 #define rfbEncodingZlibHex 8
+#ifdef BACKCHANNEL
+#define rfbEncodingBackChannel 15
+#endif
 
 /*
  * Special encoding numbers:
@@ -508,7 +513,6 @@ typedef struct {
 #define rfbTightFilterPalette          0x01
 #define rfbTightFilterGradient         0x02
 
-
 /*- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  * XCursor encoding. This is a special encoding used to transmit X-style
  * cursor shapes from server to clients. Note that for this encoding,
@@ -604,6 +608,10 @@ typedef struct {
 
 #define sz_rfbServerCutTextMsg 8
 
+#ifdef BACKCHANNEL
+typedef rfbServerCutTextMsg rfbBackChannelMsg;
+#endif
+
 
 /*-----------------------------------------------------------------------------
  * Union of all server->client messages.
diff --git a/rfbserver.c b/rfbserver.c
index 34ac38e..94533f3 100644
--- a/rfbserver.c
+++ b/rfbserver.c
@@ -1460,3 +1460,29 @@ rfbProcessUDPInput(rfbScreenInfoPtr rfbScreen)
 	rfbDisconnectUDPSock(rfbScreen);
     }
 }
+
+#ifdef BACKCHANNEL
+void rfbSendBackChannel(rfbScreenInfoPtr rfbScreen,char* str,int len)
+{
+    rfbClientPtr cl;
+    rfbBackChannelMsg sct;
+    rfbClientIteratorPtr iterator;
+
+    iterator = rfbGetClientIterator(rfbScreen);
+    while ((cl = rfbClientIteratorNext(iterator)) != NULL) {
+        sct.type = rfbBackChannel;
+        sct.length = Swap32IfLE(len);
+        if (WriteExact(cl, (char *)&sct,
+                       sz_rfbServerCutTextMsg) < 0) {
+            rfbLogPerror("rfbSendServerCutText: write");
+            rfbCloseClient(cl);
+            continue;
+        }
+        if (WriteExact(cl, str, len) < 0) {
+            rfbLogPerror("rfbSendServerCutText: write");
+            rfbCloseClient(cl);
+        }
+    }
+    rfbReleaseClientIterator(iterator);
+}
+#endif
diff --git a/x11vnc.c b/x11vnc.c
index 443d246..7181d75 100644
--- a/x11vnc.c
+++ b/x11vnc.c
@@ -232,8 +232,8 @@ int probeX=0,probeY=0;
 
 void probeScreen(rfbScreenInfoPtr s,int xscreen)
 {
-  int i,j,pixel,i1,j1,
-    bpp=s->rfbServerFormat.bitsPerPixel/8,mask=(1<<bpp)-1,
+  int i,j,/*pixel,i1,*/j1,
+    bpp=s->rfbServerFormat.bitsPerPixel/8,/*mask=(1<<bpp)-1,*/
     rstride=s->paddedWidthInBytes;
   XImage* im;
   //fprintf(stderr,"/%d,%d",probeX,probeY);
@@ -316,6 +316,13 @@ int main(int argc,char** argv)
       send_message(&single_instance,"l");
       exit(0);
     } else
+#ifdef BACKCHANNEL
+    if(i<argc-1 && !strcmp(argv[i],"-backchannel")) {
+      sprintf(message,"b%s",argv[i+1]);
+      send_message(&single_instance,message);
+      exit(0);
+    } else
+#endif
 #endif
     if(i<argc-1 && strcmp(argv[i],"-display")==0) {
       fprintf(stderr,"Using display %s\n",argv[i+1]);
@@ -459,6 +466,10 @@ int main(int argc,char** argv)
 	    break;
 	  }
       }
+#ifdef BACKCHANNEL
+      else if(message[0]=='b')
+	rfbSendBackChannel(screen,message+1,strlen(message+1));
+#endif
     }
 #endif