Direct chat is a peer-to-peer python terminal based chat app which doesn't rely on a third party server.
A: Exchange IPs with someone else. Then enter them within the same minute.
A: Not yet.
A: Via UDP holepunching, without a rendezvous server. Both peers send a UDP packet to each other at around the same time, and both NATs think that the recieved packet is a response to the packet that was sent, so they allow more incoming packets from the other peer, establishing a connection.
A: Firstly, make both sides entered the correct IP. If you're sure of that, symmetric NATs, cellular networks, VPNs and firewalls may not allow this work.
A: Not yet, this will be added in the future.
A: Very fast, since the packet is sent directly from one peer to another, without having to go through a server.