This question has been asked previously but not recently and not with a clear answer.

Using Socket.io, is there a maximum number of concurrent connections that one can maintain before you need to add another server?

Does anyone know of any active production environments that are using websockets (particularly socket.io) on a massive scale? I'd really like to know what sort of setup is best for maximum connections?

Because Websockets are built on top of TCP, my understanding is that unless ports are shared between connections you are going to be bound by the 64K port limit. But I've also seen reports of 512K connections using Gretty. So I don't know.