How to Open a Port in Linux

In networking on computers, an internet service or application’s network identification can be identified by the number of ports, which is a virtual concept. To try to connect to a network data socket or connection or outlet, the number —a 16-bit integer with a value between 0 and 65535—must be merged with the address of the Internet Protocol (IP).

If you happen to apply firewall software, say Iptables, Uncomplicated Firewall (UFW), or Firewalld, you can open ports quickly or channels or connections from a command line interface if it’s necessarily forwarded inbound or external communication to your system running on Linux.

Adjusting your firewall configuration or settings file is the only way to add rules that allow firewalls to access ports for products such as ConfigServer Firewall (CSF) Advanced and Policy Firewall (ADP). You can discover methods to configure and close ports on five of the most prominent firewalls for Red Hat, Fedora, Ubuntu, Debian, CentOS, and other Linux distributions.

Things to Be Concerned Of.

  1. Each firewall software developed for Linux will effortlessly enable TCP and UDP ports.
  2. Usually, Linux systems offer Iptables preinstalled or already set up, and the rule is quite simple to configure.
  3. If you’re working with Firewalld, performing improvements through firewall-cmd commands along with the --permanent flag or parameter promises, they aren’t altered while the firewall stops functioning and is relaunched.

There are several methods to enable ports for your firewall and Linux distribution. Each of the three most frequent circumstances or instances or conditions will be discussed in the categories that are as follows.

  • On Ubuntu-based distributions, the UFW firewall.
  • firewalld on RHEL-based distributions consisting of CentOS.
  • The iptables program can be implemented on computer systems without UFW or Firewalld.
Open a Port in Linux
Open a Port in Linux

How to Check Port Status in Linux?

In the Linux operating system, there are quite a few manners for confirming the operational state of a port, channel, or connection. Several of the most commonly employed methods are listed here.

Implementation of Netstat command: A well-known networking or connectivity command called netstat may convey several networking information, including the number of opened ports. The subsequent syntax or format can potentially be performed when executing the netstat command or operation to validate a particular port’s current condition or status.

Netstat -tulpn | grep LISTEN code example

The grep LISTEN filter enables the netstat initiatives or programs to show only those ports that are in the LISTEN state, in contrast to the -tulpn flags enabling the command itself to highlight all listening or hearing ports.

Implementation of the ss command: The most recent version of the netstat command or operator or program is the ss command. It also comes with a few extra capabilities, like the capacity to demonstrate the procedure identification number (PID) of an operation monitoring on a port. It presents an additional condensed or simplified and easier-to-read output. A particular syntax, phrase, or format might be performed when executing the ss command to determine the current condition of a port.

Example of ss Code or operator

ss -tulpn | grep LISTEN

Implementation of the lsof command or operator: A command-line tool named lsof can be implemented to report every single opened file and socket on an operating system. Mentioned throughout this are sockets or terminals or connections or ports that continually monitor for connections on designated ports. You would apply the syntax below for executing the lsof command to validate the current condition of a port.

Example of the lsof code or operator

lsof -i -P -n | grep LISTEN

This command’s output will give simple listening sockets on network interfaces. The -P parameter or flag informs the program to highlight the PID of the process utilizing every socket and the -n flag informs the command to provide addresses or domains and port numbers for each socket in numerical representation.

Significantly up to you what technique you prefer when attempting to verify the present state of a particular port in Linux. Whereas the ss command is more concise and easy to execute, netstat is one of the most frequently executed. The greatest largest amount of data can be obtained by the lsof command, even though interpreting it can be more difficult.

Whenever conducting any of these commands to determine the port status, you may obtain what results appear in one of these instances, such as.

Netstat Code Example

$ netstat -tulpn | grep LISTEN
tcp 0 0* LISTEN 2227/nginx
tcp 0 0* LISTEN 2227/nginx

This outcome reveals that ports 80 and 443 are accessible and prepared to receive inquiries. Moreover presented is the PID of the operation, which has been responding on every port.

Ss Code Example

$ ss -tulpn | grep LISTEN
LISTEN 0 0 *:* users:(("nginx",2227,"/usr/sbin/nginx"))
LISTEN 0 0 *:* users:(("nginx",2227,"/usr/sbin/nginx"))

Along with the username and procedure Identification of the operation listening for every port, the final result or output is comparable to what came before it.

lsof Code example

$ grep LISTEN | lsof -i -P –n
nginx 2227 root 3u IPv4 0xb389853a 0t0 TCP *:80 (LISTEN)
nginx 2227 root 4u IPv4 0xb389854e 0t0 TCP *:443 (LISTEN)

The data included in both previous outputs are equally provided in this particular output, including the component or device number and node or network identification associated with every socket, or channel, or connector.

How to Open Ports in Linux?

The procedure needed for activating ports in Linux is outlined here.

Determine whether the connection through the port has been declared open. The netstat command, which stands for netstat, might be implemented to show every open port on your system. All accessible ports connected to TCP will be revealed by the command below.

Example Code

netstat -an | grep LISTEN

Specify what kind of firewall you are using right now. The Iptables and firewalls are the two fundamental firewalls applied to Linux. Perform the following commands to determine which firewall you are utilizing:

Example Code

which iptables

You are using iptables if the command produces a destination address. You are running firewalld if the command you type produces no address.

Run iptables to allow access to the port. The command that follows can be employed for opening a port if you make use of iptables:

Example Code


In this instance, you might execute an equivalent command to access port 8080.

Example Code

iptables -A INPUT -p tcp -dport 8080 -j ACCEPT

Run firewalld to allow access to the port. The syntax that follows can be executed to open a port if firewalld has been enabled:

Example Code

firewall-cmd --zone=public --add-port=[port number]/tcp

In this instance, you would execute the subsequent command to enable port 8080.

Example Code

firewall-cmd --zone=public --add-port=8080/tcp

Save the firewall’s configuration adjustments. You need to back up the firewall’s modifications after enabling the appropriate port. Perform the following command to achieve this.

Example of the Code

firewall-cmd --reload

The connection to the port will continue to be enabled whenever you successfully save the changes. Consider a couple more essential things when accessing ports on the Linux operating system.

Always enable the ports that need to be opened for whatever services you execute, and if attainable, maintain these available for as little duration as necessary. 

It would help to use a robust firewall to safeguard against unapproved entry into your system.

How to Open Ports in Ubuntu-based Systems?

In Ubuntu-based systems as a whole, there are actually a couple of methods to access ports: by implementing the Uncomplicated Firewall (UFW) or by using iptables.

Implementing about UFW

UFW is a fundamental firewall that is simple to configure and set up. Execute one of the following commands for accessing a port with UFW:

Syntax of the Code

sudo ufw allow <port>

For example, you might execute the following command to enable port 50.

Example Code

sudo ufw allow 50

You can open a selection of ports by setting the beginning and completion ports. For example, you could execute the subsequent command to reveal ports 50 and 440.

Example Code

sudo ufw allow 50:440

Whenever a port has been opened up, you can execute the following commands to ensure it is open.

Example Code

sudo ufw status

Implementing about iptables

Whereas iptables is an even more sophisticated firewall than UFW, implementing it is a bit harder. Through iptables, you can send out one of the following commands to open a port.

Syntax of the Code

sudo iptables -I INPUT -p tcp -m tcp --dport <port> -j ACCEPT

For example, you might execute the subsequent command to access port 50.

Example Code

sudo iptables -I INPUT -p tcp -m tcp --dport 50 -j ACCEPT

You may also open any number of ports by choosing both beginning and ending ports. For example, you could execute the command to access ports 50 and 440.

Example Code

sudo iptables -I INPUT -p tcp -m tcp --dport 50:440 -j ACCEPT

Whenever a port has been officially opened up, you might execute a command like this to prove it’s available.

Example Code

sudo iptables -L

How to Open Ports in Cent OS-based Systems?

Implementing iptables or firewalld are two distinct methods for accessing ports in CentOS-based workstations.

Employing iptables Code

Authenticate or login into the server’s root.

To access port 50, perform the following command.

Example of the Code

/sbin/iptables -I INPUT -p tcp --destination-port 50 -j ACCEPT

iptables rules or principles must be saved

Example Code

/sbin/service iptables save

To make sure that the port has been opened, evaluate the iptables principles or principles:

Example Code

/sbin/iptables -S

Employing firewalld

Inspect the firewall’s status.

Example Code

systemctl status firewalld

The zones that are active or operational

Example Code

firewall-cmd --list-all-zones

Ports 50 and 440 ought to remain operational in the public region.

Example Code

firewall-cmd --zone=public --add-port=50/tcp --add-port=440/tcp

Extending or reloading the firewall rules

Example Code

firewall-cmd --reload

Ensure that the ports of entry are readily available and represented in the relevant zone:

Example Code

firewall-cmd --list-ports

How to Open Ports in Other Linux Distributions?

The steps needed for activating ports in different distributions of Linux have been outlined.

Ubuntu and Debian

Activate the command prompt or terminal window.

Perform the following command or operation to enable TCP traffic across the port.

Example Code

sudo ufw allow 1191/tcp

Execute the command that appears below to make available a certain amount of ports:

Example Code

sudo ufw allow 60000:61000/tcp

Make use of the following commands to cease operations and activate the Straightforward Firewall (UFW):

Example Code

sudo ufw disable
sudo ufw enable

Firewalld on CentOS and additional systems

Activate the command prompt or terminal window.

To permit TCP traffic over the port, submit the following command:

Example Code

firewall-cmd --zone=public --add-port=1191/tcp --permanent

Execute the command that appears below to make available a couple of ports:

Example Code

firewall-cmd --zone=public --add-port=60000:61000/tcp --permanent

Submit the subsequent command to reload or reactivate the firewall rules:

Example Code

firewall-cmd --reload

Operating Systems Running Linux absent of firewalls or UFW

Activate the Command prompt or terminal window.

If you want to edit or modify the iptables firewall configuration, enter the command described in the following.

Example Code

sudo vi /etc/sysconfig/iptables

Provide the following line in the document or file.

Example Code

-A INPUT -p tcp -m tcp --dport 1191 -j ACCEPT

After saving the document, dismiss the window for editing.

Perform the contents of the following command for reloading or resetting the iptables rules:

Example Code

sudo service iptables restart
  1. Are there open ports available on the operating system Linux?

    Display every open port. On the Linux operating system, you have to initially look at the listing of all ports that are open and find an ephemeral port that does not have anything on it before launching it. The most commonly used methods or protocols for packet transfer at the network layer, TCP and UDP, are capable of being listed through the netstat command, which stands for netstat.

  2. What is the command that Linux uses to initiate communication with a port?

    For the opening of ports, perform the command netstat -tulpn. On newer Linux distributions or operating systems, using ss -tulpn to allow ports is another option to consider.

  3. How does Linux deal with ports?

    In the Linux operating system, the term “port” is a metaphorical or symbolic idea that promotes communication with several network-related services. It is a 16-bit integer with an integer range of zero through the number 65535, which has no physical form. A socket or socket domain or address has been generated by combining a port with an internet protocol address. It establishes a relationship between the client’s device and the server’s system.

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