XEP-0065 is supported. Currently jabber.el cannot act as a server, not even on on Emacsen that support server sockets (GNU Emacs 22 and up). Therefore it relies on proxies. Proxies have to be entered and queried manually.
Psi's “fast mode” (http://delta.affinix.com/specs/stream.html), which gives greater flexibility with regards to NAT, is not implemented.