[Ndymium]

A connection is identified by the tuple {host IP, host port, client IP, client port}. The server listens on one port, but the client has a separate port for each connection. This means that there can be 65k connections for a single {host IP, client IP} combination.

There's two ways to get more connections: use more client IPs or use more host IPs. In this post the OP has decided to add more host IPs.

[miyuru]

That means this benchmark is useless right?

In real world there will be more client IPs and the host will be listening on 1 IPv4 on 1 port.

[Ndymium]

That would depend on if it matters to the WebSocket server if connections are from one or multiple IPs. In this case I would not think that there's any difference as far as the WS library is concerned. Maybe it has some effect on the OS kernel's networking routines, but I would not expect it to be big.