#Open port on linux
iptables -A INPUT -p tcp --dport 9000 -j ACCEPT
# for specific ip
iptables -I INPUT -p tcp -s 153.403.145.229 --dport 9000 -j ACCEPT
Open port in iptables
What is Iptables?
Iptables is a set of rules that allows a system administrator to configure the tables provided by the Linux kernel firewall and the chains and rules it stores. Iptables almost always comes pre-installed on any Linux distribution.Having a properly configured firewall is very important for the overall security on your server.
What is a port?
A computer port is a type of electronic, software- or programming-related docking point through which information flows from a program on your computer or to your computer from the Internet or another computer in a network.