[ros-users] map saver problem

hi i am trying to run the gmapping from logged data tutorial. I have
downloaded the base_localisation bag from willow garage and followed the
rest of tutorial but I am not able to save the map, when i run rosrun
map_server map_saver map:=dynamic_map
i get [ INFO] 0.000000000: Waiting for the map and thats all nothing happens
after this.

So please help me as I am not able to fix this.

--shayan