--- a/src/main/java/jp/ac/u_ryukyu/treevnc/BroadcastRFBListener.java	Fri Feb 22 15:42:41 2019 +0900
+++ b/src/main/java/jp/ac/u_ryukyu/treevnc/BroadcastRFBListener.java	Fri Feb 22 16:07:03 2019 +0900
@@ -44,11 +44,11 @@
 		} catch (SocketException e) {
 			System.out.println("join to " +  Ipv4McastAddr + " failed.");
 		}
-		try {
+		/*try {
 			soc.joinGroup(InetAddress.getByName(Ipv6McastAddr));
 		} catch (SocketException e) {
 			System.out.println("join to " +  Ipv6McastAddr + " failed.");
-		}
+		}*/
         return soc;
     }
 
@@ -58,37 +58,37 @@
 	 */
 	private void rfbBroadcastLoop() {
 		byte[] buf = new byte[BufSize];
-		try {
 
-            DatagramPacket recvPacket = new DatagramPacket(buf, BufSize);
-            while (!stopFlag) {
+		DatagramPacket recvPacket = new DatagramPacket(buf, BufSize);
+		while (!stopFlag) {
+			try {
 				soc.receive(recvPacket);
 				String hostname = recvPacket.getAddress().getHostAddress();
-		        byte[] reply = recvPacket.getData();
+				byte[] reply = recvPacket.getData();
 				int len = recvPacket.getLength();
 				boolean isTreeRoot = rfb.isTreeManager();
-				if (isTreeRoot && receiverTask != null ) {
+				if (isTreeRoot && receiverTask != null) {
 					receiverTask.setReader(new Reader(new ByteArrayInputStream(reply)));
 					if (receiverTask.getMessageId() == FRAMEBUFFER_UPDATE) {
 						receiverTask.framebufferUpdateMessage();
 					}
 				}
+			} catch (Exception e) {
+				System.out.println("broadcast-rfb-listener :" + e.getMessage());
 			}
-		} catch (Exception e) {
-            System.out.println("tree-root-find-listener :" + e.getMessage());
 		}
 	}
 
 	public void multicastUpdateRectangle(ByteBuffer buf) {
 
-		try {
+		/*try {
 			DatagramPacket sendPacket = new DatagramPacket(buf.array
 					(), buf.limit(), InetAddress.getByName(TreeRootFinderListener.Ipv6McastAddr), ConnectionParams.DEFAULT_VNC_BROADCAST);
 			soc.send(sendPacket);
 		} catch (IOException e) {
 			System.out.println("cannot send UpdateRectangle.");
 			e.printStackTrace();
-		}
+		}*/
 
 		try {
 			DatagramPacket sendPacket1 = new DatagramPacket(buf.array(), buf.limit(), InetAddress.getByName(TreeRootFinderListener.Ipv4McastAddr), ConnectionParams.DEFAULT_VNC_BROADCAST);