Just in case someone finds this useful. Please expand/correct
This will give you the host name of the database/instance you are connected to (which may be a remote server)
select host_name from v$instance;
This will give you the local host name, irrespective of the database/instance you are connected to
select SYS_CONTEXT('USERENV', 'HOST') host_name from dual;
(Oracle 11g, probably earlier)