UTL_INADDR ORA-29257:host [ip or name] unknown

In Oracle there is UTL_INADDR package that is an API to access host name and ip address of server.
Usage

select UTL_INADDR.get_host_name('host_name') from dual;
select UTL_INADDR.get_address_name('ip_address') from dual;

SET serveroutput on
BEGIN
  DBMS_OUTPUT.PUT_LINE(UTL_INADDR.GET_HOST_NAME);  -- get local host name
  DBMS_OUTPUT.PUT_LINE(UTL_INADDR.GET_HOST_ADDRESS);  -- get local IP addr
END;
/

If host_name or ip_address is null, this function returns local host hostname or ip.
If hostname or IP can't be resolved, error ORA-29257:host [ip or name] unknown is returned.