Since you are able to connect to the database, through sqlplus that shows that the listeners are up and functional.

To connect to the server manager fist you would have to

set ORACLE_SID=bob
svrmgrl##
svrmgr> connect internal


I would suggest that you get accoustom to that of using sqlplus to do the administration as svrmgrl had been discontinued as of 9i.

set your ORACLE_SID
sqlplus "/ as sysdba"


Good luck.
Sam