Kurento binds somehow always to the external IP instead of the local one or 0.0.0.0
. For that reason you need to add your external IP to your interface.
$ ip addr add 144.76.97.34/32 dev ens3
Specific to your linux distribution. Use a search engine of your choice. ;)
Also don't forget to forward all necassary ports listed in http://docs.bigbluebutton.org/2.2/configure-firewall.html