Erm, i'm confused, is ngrok really currently proxying 17 million tunnels? How are they supporting so many IPv4 tunnels? Presumably they don't have the IPv4 spa

Erm, i'm confused, is ngrok really currently proxying 17 million tunnels? How are they supporting so many IPv4 tunnels? Presumably they don't have the IPv4 space to assign standard ports to them. HTTP is easy but they say they let you "expose any networked service". Why are folks only worried about the closed source client, which likely does nothing interesting, when all the magic must be at the backend?