[jsk_naoqi_robot/cross/README] add information how to handle several …

…sessions

jsk_naoqi_robot/cross/README.md

@@ -95,6 +95,15 @@ ssh to NAO_IP machine and run this command directly under the home directory.
 
 If you want to attach the session again, please execute `./User/attach.sh`.
 
+If there are several sessions like this (You can see same outputs with `screen -c User/screenrc -ls`.):
+```
+There are several suitable screens on:
+	31164.session	(04/04/14 12:28:31)	(Detached)
+	29334.session	(04/04/14 12:26:33)	(Detached)
+Use -S to specify a session.
+```
+Please specify a session like `screen -c User/screenrc -r 31164` and it is recommended to close all sessions one by one.
+
 You can connect to `app_chooser` by http://<$NAO_IP>:8000/rwt_app_chooser/#!robot
 
 Also, you can access to running ROS process on Pepper from your remote PC by typing `rossetmaster <$NAO_IP>`