[DanielHB]

if you really want maximum performance maybe consider using CoAP for node-communication:

https://en.wikipedia.org/wiki/Constrained_Application_Protoc...

It is UDP-based but adds handshakes and retransmissions. But I am guessing for your benchmark transmission overhead isn't a major concern.

Websockets are not that bad, only the initial connection is HTTP. As long as you don't create a ton of connections all the time it shouldn't be much slower than a TCP-based socket (purely theoretical assumption on my part, I never tested).