Opening Ports in a Linux Firewall

This guide applies only to users of Linux based operating systems.

The procedure for opening ports in the Linux firewall "iptables" is relatively simple.

First, open a command-line terminal.  In most systems, you can usually find this in your 'Applications' menu under the 'System Tools' section.

Once you have a terminal open, you have to obtain root access to change firewall settings.  Do this by typing:
 

su -

You will be prompted for your root password.

In the following examples, substitute the port # you want to open for the 12345 in the command.

If you want to open an incoming TCP port, type the following:
 

iptables -I INPUT -p tcp --dport 12345 --syn -j ACCEPT

If you want to open a UDP port (perhaps for DHT in Tixati), type the following:
 

iptables -I INPUT -p udp --dport 12345 -j ACCEPT

After you are done opening ports in your firewall, you can save your changes so they will be applied when you restart your computer by typing the following command:
 

service iptables save

That's it!  If you have any questions or comments about this guide, please feel free to drop us a note on the Support and Feedback page.

If you also have a broadband NAT router for your internet connection and want to configure it to forward incoming TCP connections or UDP packets, read the Forwarding Ports In a Broadband Router guide.
 

原文链接 ：  https://www.tixati.com/optimize/open-ports-linux.html