--- a/src/main/java/jp/ac/u_ryukyu/treevnc/client/TreeVncProtocol.java	Fri Jun 13 18:16:27 2014 +0900
+++ b/src/main/java/jp/ac/u_ryukyu/treevnc/client/TreeVncProtocol.java	Fri Jun 13 18:51:14 2014 +0900
@@ -45,8 +45,8 @@
 
 	}
 
-	public void findRootReply(String hostname, int port) throws IOException {
-		sendWithHostAndPort(ProtocolContext.FIND_ROOT_REPLY, hostname, port);
+	public void findRootReply(int port) throws IOException {
+		sendWithHostAndPort(ProtocolContext.FIND_ROOT_REPLY, null, port);
 	}
 
 	public void whereToConnect(String hostname, int port) throws IOException {
@@ -65,6 +65,11 @@
 	public void sendWithHostAndPort(int command, String hostname, int port)
 			throws IOException {
 		openport();
+		if (hostname == null) {
+			// in case of root finder, we can't get localaddress from datagram packet.
+			// so use local part of TCP socket.
+			hostname = echoSocket.getLocalAddress().getHostAddress();
+		}
 		int cmdlen = 4+4+4+hostname.length();
 		if (cmdlen < 12) cmdlen=12;
 		ByteBuffer buf = ByteBuffer.allocate(cmdlen);

--- a/src/main/java/jp/ac/u_ryukyu/treevnc/server/TreeRootFinderListener.java	Fri Jun 13 18:16:27 2014 +0900
+++ b/src/main/java/jp/ac/u_ryukyu/treevnc/server/TreeRootFinderListener.java	Fri Jun 13 18:51:14 2014 +0900
@@ -35,6 +35,7 @@
 			soc.joinGroup(mAddr);
 			while (!stopFlag) {
 				soc.receive(recvPacket);
+				String hostname = recvPacket.getAddress().getHostAddress();
 		        byte[] reply = recvPacket.getData();
 				int len = recvPacket.getLength();
 				if (len != 12) {
@@ -49,9 +50,9 @@
 				port = port * 256 + reply[10];
 				port = port * 256 + reply[11];
 				
-				TreeVncProtocol t = new TreeVncProtocol("", port);
+				TreeVncProtocol t = new TreeVncProtocol(hostname, port);
 				try {
-					t.findRootReply(getMyAddress(), vps.getRfb().getAcceptPort());
+					t.findRootReply(vps.getRfb().getAcceptPort());
 				} catch (IOException e) {
 					e.printStackTrace();
 				}