diff --git a/libvncserver/main.c b/libvncserver/main.c
index 96aeda7..0c87d8e 100644
--- a/libvncserver/main.c
+++ b/libvncserver/main.c
@@ -498,6 +498,11 @@ enum rfbNewClientAction rfbDefaultNewClientHook(rfbClientPtr cl)
 	return RFB_CLIENT_ACCEPT;
 }
 
+rfbBool rfbDefaultProcessCustomClientMessage(rfbClientPtr cl,uint8_t type)
+{
+	return FALSE;
+}
+
 /*
  * Update server's pixel format in screenInfo structure. This
  * function is called from rfbGetScreen() and rfbNewFramebuffer().
@@ -641,6 +646,7 @@ rfbScreenInfoPtr rfbGetScreen(int* argc,char** argv,
    screen->setTranslateFunction = rfbSetTranslateFunction;
    screen->newClientHook = rfbDefaultNewClientHook;
    screen->displayHook = 0;
+   screen->processCustomClientMessage = rfbDefaultProcessCustomClientMessage;
 
    /* initialize client list and iterator mutex */
    rfbClientListInit(screen);
diff --git a/libvncserver/rfbserver.c b/libvncserver/rfbserver.c
index 33e277d..0e6a4ce 100644
--- a/libvncserver/rfbserver.c
+++ b/libvncserver/rfbserver.c
@@ -1039,6 +1039,9 @@ rfbProcessClientNormalMessage(cl)
 
     default:
 
+	if(cl->screen->processCustomClientMessage(cl,msg.type))
+		return;
+
         rfbLog("rfbProcessClientNormalMessage: unknown message type %d\n",
                 msg.type);
         rfbLog(" ... closing connection\n");
diff --git a/rfb/rfb.h b/rfb/rfb.h
index d97cd19..dd61660 100644
--- a/rfb/rfb.h
+++ b/rfb/rfb.h
@@ -125,6 +125,7 @@ typedef rfbBool (*rfbSetTranslateFunctionProcPtr)(struct _rfbClientRec* cl);
 typedef rfbBool (*rfbPasswordCheckProcPtr)(struct _rfbClientRec* cl,const char* encryptedPassWord,int len);
 typedef enum rfbNewClientAction (*rfbNewClientHookPtr)(struct _rfbClientRec* cl);
 typedef void (*rfbDisplayHookPtr)(struct _rfbClientRec* cl);
+typedef rfbBool (*rfbProcessCustomClientMessageProcPtr)(struct _rfbClientRec* cl,uint8_t type);
 
 typedef struct {
   uint32_t count;
@@ -291,6 +292,10 @@ typedef struct _rfbScreenInfo
      * an update should be sent. This should make working on a slow
      * link more interactive. */
     int progressiveSliceHeight;
+
+    /* if LibVNCServer doesn't know the normal message, it calls this
+     * hook. If the hook handles the message, it returns TRUE. */
+    rfbProcessCustomClientMessageProcPtr processCustomClientMessage;
 } rfbScreenInfo, *rfbScreenInfoPtr;