1. Download the Oracle XE deb package (free registration is required).
2. Double click the downloaded file and select to install it.
3. In terminal run sudo /etc/init.d/oracle-xe configure.
4. You will be prompted to enter the following parameters: HTTP port number, database listener port number, SYSTEM and SYS database accounts password and whether the service should be started upon boot.
5. Thereafter the configuration might take a few minutes. That’s it. To start the service in the future run sudo /etc/init.d/oracle-xe start and to stop sudo /etc/init.d/oracle-xe stop.

select 'Hello ' || '&name' from dual
union all
select 'Goodbye ' || '&name' from dual;

To prompt for any given variable only once and use the entered value multiple times use two ampersands instead of one. The query below will prompt for the variable “name” once only:

select 'Hello ' || '&&name' from dual
union all
select 'Goodbye ' || '&&name' from dual;

To prevent prompting altogeher, use the set define command:

set define off
select 'Hello world & dog' from dual;

SQL> select dbms_xdb.gethttpport from dual;

In order to change the port number, run the following SQL (the port is changed to 8181 in the example below) and restart the database:

SQL> begin
dbms_xdb.sethttpport('8181');
end;
/


If you want to disable the HTTP access altogether, you can set the port number to 0.

There are also similar methods dbms_xdb.getftpport and dbms_xdb.setftpport, although I am not sure in what context FTP is used with Oracle XE. By default the port is 0, i.e. disabled.