Since Firebird1 you can specify port number directly in connect string:
myserver/3052:c:\mydb.fdb

In _any_ Firebird/InterBase version you can specify port number indirectly,
using "services" file (it works e.g. in IB5.6):

myserver/gds_db2:c:\mydb.fdb

provided "services" contains this line:

gds_db2 3052/tcp


Ivan Prenosil
http://www.volny.cz/iprenosil/interbase

----- Original Message -----
From: "Jonathan Neve" <jonathan@...>
> Apparently, it's possible with FireBird to set the port number in the
> connexion string. Is that right?
> If so, starting from which version.
>
> Also, can a FireBird 1.0 or 1.5 client machine communicate with an IB
> 6.0 server? Because I wouldn't mind upgrading the client machines if
> necessary, but I wouldn't like to touch the server.