I tried to use file sharing and chat over home network. Adding both local addresses and ports (both with and without extra port) into settings on two computers does absolutely nothing (and there is no indication that anything should happen, there is no change in the list of peers, no log messages, etc.). The same happens with two different instances on the same computer.

What might be important is that ISP NAT does not support hairpinning. Therefore, you can't see your own share, nor chat with yourself, because you're always “offline” (unreachable) from the same address as destination. I suppose that peers use public addresses as main communication channel even when they are on the same LAN, and local connection is a secondary shortcut created afterwards.

It might also be important that I used a number of recent 32 bit FOPNU versions because old systems were involved.