Connecting to an Interbase DB online via Java/Interclient

I have Interbase set up on my local machine and it works fine, but
when I try to put a database online and connect to it (via
Java/Interclient), I get this error:
interbase.interclient.CommunicationException: [interclient]
Communication error:
 A socket exception occurred while trying to establish a socket
connection to se
The message of the SocketException is "Connection refused: no further
See API reference for exception
I've put the interclient.jar file in the same directory as the
database, and I'm connecting to
So I guess my questions are:
- Is this possible at all?  I searched the archives for this group,
and when other people were having the same problem, the suggestion was
that they needed to enable Interserver on their (local) machine.  If
this is the only way, it's not really an option if I'm connecting to
somebody else's server ...
- If it is possible, could somebody either connect to the db at that
URL (it's just one record in a table called 'stock'), and try to tell
me what I'm doing wrong?  Or if somebody else has a DB online that I
could use for testing, it would be most appreciated.  (Although
probably if you have a DB online you don't want somebody messing with
it, but I thought I'd ask).  For test.db, the username is the default
'SYSDBA' and the password is 'masterkey'.