As said by Ook!

Using ICQ2000(b) I had to open up some port for transfers/chats like mentioned in the 2 prior links.
I installed ICQ2001 last week and (ofcourse) I used the same connect and transfer ports as I did with 2000b. 2001 went online OK, but file transfers, chats and the (new) ICQ shared file system didn't work at all ("Can't establish a direct connection").

After some playing around with the available ports I noticed that when I set everything to default on the "User" tab (Connections settings) it all works great!
I stopped forwarding any ports on my router for ICQ and checked again, and, strangely, everything worked ok.
I think ICQ has found some nice way to work without any firewall settings at all; I've only changed 1 setting on the Server tab ("Not using firewall" to "Using firewall, not using proxy") and it just works great behind a router.. even the ICQ shared folder works like it's supposed to.

got feedback? got feedback?

Any feedback you provide is sent to the owner of this FAQ for possible incorporation and shown publically as well.

by Greywolf