One important note: If ur node is visible on the Internet then launch client by
java -cp Nxt.zip Nxt IP_ADDRESS
Right now only 1 bootstrapping node runs the newest version. If it goes down the network will be fragmented.
If I don't have a static IP, would it work if I set up dynamic DNS and use hostname instead of IP_ADDRESS? What ports should be opened if behind a router/firewall, is 7874 enough?
Privacy questions: Can an attacker monitoring your traffic (i.e. your ISP) learn your account number, if you just log in (at localhost:7875), without sending transactions? Is your IP being recorded in the blockchain when performing transactions, thus exposing your account number? If so, could one connect using tor / socks proxy, like for example the bitcoin-qt client allows?
DNS name should work as long as it's resolved to ur IP. 7874 for peers, 7875 for client and 7876 for API reqeusts.
Noone can see ur account id if u use localhost to unlock the account. Dunno if blockchain saves ur IP though. But, if u send a transaction then connected peers can see who is the sender and they already know ur IP. Tor should work for Nxt.