We were trying to install "Big blue button" in an Ubuntu server with a firewall. For installation, we need these UDP ports ("16384-32768") should be opened in the firewall. But we don't know whether the udp ports are opened or not in the firewall. When we tried the "netcat" service, we were able to communicate. But while doing "nmap" scanning, it has been showing these UDP ports in the state as "closed"
nmap command used as :
nmap -sS -sU -PN -p 16384 EXTERNAL_IP ( For single port )
Host is up (0.039s latency). PORT STATE SERVICE 16384/tcp filtered connected 16384/udp closed connected