Open or close server ports

Open server ports for remote access

In many cases, it is necessary to open additional ports for your application(s) to function correctly.

If you are using iptables, use the following command to open port 21:

$ iptables -A INPUT -p tcp --dport 21 -j ACCEPT

If you are using ufw, use the following command to achieve the same result:

$ sudo ufw allow 21

Close server ports and deny remote access

In some cases, it is necessary to close ports for your application(s) to increase security.

If you are using iptables, use the following command to close port 21:

$ iptables -A INPUT -p tcp --dport 21 -j DROP

If you are using ufw, use the following command to achieve the same result:

$ sudo ufw deny 21