Thank you Giuseppe, NOW IT WORKS!
Switching to 6.0.3, we would not like to adapt our existing Internet pages with the new sintax, it is preferable to leave the ones that worked with the previous version of Lighstreamer. I see that the Javascript code in the pages uses: LScommons.js, LSpushpage.js and misc.js. Should I copy these files to the same folder as the HTML pages? These files are not present in the distribution of Lighstreamer 6.0.3, should I take them from an older distribution?

Thank you! Paolo