Dear Thomas and Konstantin,

thank you very much for the feedback. I found the ROOTANA javascript display a good source of 
information and references.

As Thomas said, maybe the simplest thing would be to use the ROOT THttpServer. Honestly, I do 
not think that ROOT was ever meant to act as an online monitor due to its wacky memory 
management and abysmal multithread support. In other words, I think that by using ROOT we would 
inevitably lose some performance. 

Perhaps there are better ways of achieving the same goal. For example, I was leaning towards a 
plotly.js based approach where I would encode a series of vectors in base64 strings (for better 
transmission performance), send them to the client through the MJSONRPC mechanism, decode them 
and then feed them to plotly.js. But in this case, I should study many new libraries 
(plotly.js, the library for the base64 encoding, the Gaussian fitting, etc...) and I do not 
have the time to do that now: "beam is coming".

So ROOT it is. I will use the ROOTANA javascript display as a reference. Do you happen to know 
who wrote that part? 

In that example, you have some "static" histograms that you keep always in memory, while in our 
case the number of channels is so big that we have to dynamically generate the histograms only 
when needed (when the user select a single channel).

Best regards
Giorgio