There is definitely a server involved with establishing the direct connection
Just had an hour long, serverless, encrypted, low latency video call on mobile with nostr:npub1h8nk2346qezka5cpm8jjh3yl5j88pf4ly2ptu7s6uu55wcfqy0wq36rpev over #Keet 🔥🔥🔥
Discussion
From what I understand, all connections are made using the DHT. It works like BitTorrent, there is no central server.