Hi guys, I like to fend for myself before asking for help.
But unfortunately I can not really.
I currently have a dedicated server, I have an Ubuntu OS 18.04 LTS server.
I decided to mount a Rust server. But nobody can join the server, except administrators with SSH access.
After several research on LinuxGSM support, "firewall, port", I suspect there is something wrong.
I guess I'm not the last or the first to have this case. I would like some help with what has already been this problem? ty

Ps: I've openned ports: 

iptables -A INPUT -m state --state NEW -m tcp -p tcp --dport 28015 -j ACCEPT
iptables -A INPUT -m state --state NEW -m udp -p udp --dport 28015 -j ACCEPT
iptables -A INPUT -m state --state NEW -m tcp -p tcp --dport 28016 -j ACCEPT