Bluez stack moved to using D-Bus almost exclusively. Check kbdd for some D-Bus shell scripting hackery for allocating rfcomm ports. See dbus-bluez-rfcomm inside kbdd.tar.gz or see wiki.bluez.org for other examples.

Advantage of using d-bus for allocating rfcomm port is that is plays nice with rest of the system, you don't need to hardcode specific rfcomm port number and hope system will not use it.