How to open network ports on a Linux server firewall

First, it is important to know the difference between TCP and UDP protocols. TCP is a connection-oriented protocol that ensures data delivery and is commonly used for web browsing, email, and file transfers. On the other hand, UDP is a connectionless protocol that doesn’t guarantee data delivery but is ideal for applications that don’t require strict reliability, such as online gaming and video streaming.

To computer” title=”How to open network ports on a computer”>open a network port on a Linux server firewall, you need to access the server’s command line interface (CLI) as a root user. The command line interface provides greater control over the system firewall compared to the graphical user interface (GUI).

Before opening a port, you must verify if the port is currently blocked. To list all open ports on your server, use the following command:

$ sudo netstat -lnp | grep ‘LISTEN’

This command lists all listening ports along with their associated protocol, process ID, and process name.

Once you’ve identified the port you want to open, you can proceed to configure your server firewall. The two most common firewall applications in Linux systems are iptables and firewalld.

Iptables is a traditional firewall application that uses a set of rules to filter network traffic. To open a port using iptables, you must minecraft-server-a-step-by-step-guide” title=”Creating a Minecraft Server: A Step-by-Step Guide”>create a rule that allows incoming traffic on the specified port. You can do this using the following command:

$ sudo iptables -A INPUT -p tcp –dport [PORT NUMBER] -j ACCEPT

This command creates a new rule that allows incoming TCP traffic on the specified port. You can replace “tcp” with “udp” to allow UDP traffic instead. Remember to replace “[PORT NUMBER]” with the actual number of the port you want to open.

After creating the new rule, you must save the configuration subsystem-for-linux-3″ title=”Windows Subsystem for Linux”>settings to make it persistent across server reboots. You can use the following command to save the iptables configuration:

$ sudo iptables-save > /etc/sysconfig/iptables

The above command saves the current iptables configuration to the /etc/sysconfig/iptables file.

Firewalld is a newer firewall application that uses zones to manage network access. Each zone represents a certain level of trust and allows incoming traffic based on predefined rules. To open a port using firewalld, you must add a new rule to the appropriate zone.

First, list all available zones using the following command:

$ sudo firewall-cmd –get-zones

This command lists all available zones on your system, such as public, home, and work. Once you’ve identified the appropriate zone, you can add a new rule to allow traffic on the specified port. Use the following command to add a new rule:

$ sudo firewall-cmd –zone=[ZONE NAME] –add-port=[PORT NUMBER]/tcp –permanent

Replace “[ZONE NAME]” with the actual name of the zone and “[PORT NUMBER]” with the number of the port you want to open. You can also use “–add-port=[PORT NUMBER]/udp” to allow UDP traffic instead.

Finally, reload the firewalld configuration to apply the changes by using the following command:

$ sudo firewall-cmd –reload

Conclusion:

Opening network ports on a Linux server firewall can be vital for certain applications to function correctly. However, it is essential to ensure that you’re opening only the required ports and limiting access to authorized sources. Implementing a firewall is always recommended to protect your server from harmful traffic. The way you open the port depends on what kind of firewall you are running- iptables or firewalld. This guide covers both ways to help you open your required network ports with ease.