In my case, i have the 2 servers (tomcat:80 and lightstreamer:8081) on the same machine.
is there any additional configuration i have to make ? (in addition to having 2 network cards)

And why do i need 2 network cards ?
use standard HTTP ports (80) for both your Web Server and your Lightstreamer Server
Does that mean that the 2 servers MUST use the same port (80) ?