I've had to do the "port forward - tunneling - port reconnect" thing for Oracle, and I'm pretty sure you can put the reconnect and initial connection on the same port, or at least you can specify a specific port where that reconnect happens. Because indeed otherwise you're left with a range of open ports or you don't know which port to tunnel on.
The database had to be in a certain mode though (Don't know if it was shared or dedicated), and some changed to the ORA file or other were necessary too to specify the port.
Oh yes, and in good Oracle fashion, this was only possible from Oracle9i, or before Oracle10 or something like that
:-)
And why it pays to be an Oracle consultants, folks
:-) (I'm not an Oracle consultant for the record).
Next lesson: try installing Oracle on a linux platform...I hope you guys know something about library linking, compiler options and make files