When I'm starting listener it is successfully starting with the default port values, but then when i change the port number and again start listener, it is still loading with same port number(1521). what could be the problem?

When i shutdown the services connected to the listener, and startup the database in nomount stage, i could not access the listener, while accessing through RMAN it is showing TNS NO Listener, but still the network connection is active between the two boxes. what is the solution for this?