I just reinstalled the forum and everything is working fine.
The links have the right url, I did not have a 403 error even without modifying config.json with socket.io origins.
While at the installation I did not change anything.
But hey, everything works fine, it's the main lol.
Thanks, i love to use NodeBB !
(I just put the url of the site when setting up the forum and not by changing config.json later as I had done the first, it may be from there?)