How do I add rules to the iptables firewall?

Some examples are given below:

To allow access to port 80 on the firewall, append the following rule:

iptables -A INPUT -p tcp -m tcp –sport 80 -j ACCEPT
iptables -A OUTPUT -p tcp -m tcp –dport 80 -j ACCEPT

This allows regular Web browsing from websites that communicate via port 80. To allow access to secure websites (such as https://www.example.com/), you must open port 443, as well.

iptables -A INPUT -p tcp -m tcp –sport 443 -j ACCEPT
iptables -A OUTPUT -p tcp -m tcp –dport 443 -j ACCEPT

To allow remote SSH access, the following rules may be used:

iptables -A INPUT -p tcp –dport 22 -j ACCEPT
iptables -A OUTPUT -p udp –sport 22 -j ACCEPT

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