[Interest] Best approach for html5 application

[Marco Trapanese]

Hello,

I've already developed several web-based application using Qt5 as engine 
for data processing. The webpages are accessed from remote terminal, 
often from smartphones. Here my current approach:

- on the server machine (often a small SBC) I run any http server, i.e. 
lighttpd
- I develop the user interface in html5 and javascript - to handle 
actions and behavior of the UI
- on the server runs also a Qt5 application which provides the 
communications with the outside world (database, local I/O, fieldbus, 
etc...)
- both the webpages and the "core" Qt5 application exchange data using a 
websocket. In this way I can transmit and receive data between the user 
side and server side

This approach works but has several drawbacks:

- it's not so easy (for me at least) to provide server side code to make 
a really dynamic pages. I found two ways: 1. send the generated html 
code through the websocket and use a javascript function to put it into 
the actual page, 2. use some server side language (i.e. cgi) and create 
another communication channel between it and the Qt5 application. 
Currently I create the contents directly from javascript, but this is 
not so safe

- the websocket(s) requires at least to open one more port than the 
default 80 and that should be forwarded to the http server

- for the same reason it's hard to have more servers in the same LAN 
because you have to forward both ports (http and websocket ones) to the 
correct local ip


That said, I have few questions:

1) in general, this is the best approach or you might suggest a better one?
2) any hint about the drawbacks?
3) until now the webservers were designed to answer to only one client, 
but in the next project the web-application should be used by dozen of 
clients at the same time (the goal is to acquire some data and put it 
into a db, taking care of which user submitted). I guess it's much 
better to put the webpages on a reliable third-party hosting provider, 
but then I'm afraid I also need to set up my own server to run the Qt5 
application

Thanks for any suggestion!
Marco