Open port Linux allows to configure firewall settings to allow the connections on specific ports for the systems which can efficiently send and receive data packets over a network.
In some cases, certain ports may be closed by default for security reasons, preventing incoming connections. In that situation, it becomes necessary to open ports in Linux to enable seamless communication. There are different methods for opening ports in Linux.
In the given below you will learn how to check port status, how to open ports in different systems.
How to Check Port Status in Linux
Checking the status of ports in Linux is essential to identify whether a specific port is open or closed. There are several methods available to accomplish this task. Let’s explore two commonly used methods in given below.
Method 1: Using the netstat command
- Open a terminal or command prompt on your Linux system.
- Type the following command.
- netstat -tuln
- This command displays a list of all active network connections and listening ports on your system.
- Search for the port number you want to check in the “Local Address” column.
- It shows the IP address and port number combination.
- If a port is open and actively listening, you will see an entry with the corresponding port number and the state “LISTEN”. This indicates that the port is open and ready to receive incoming connections.
- If a port is closed or not actively listening, it will not appear in the list.
Method 2: Using the nmap tool
- Install nmap on your Linux system if it is not already installed.
- Open a terminal or command prompt on your Linux system.
- Type the following command.
- sudo nmap -p [port number] localhost
- Replace [port number] with the actual port number you want to check.
- This command scans the specified port on the local machine.
The output will provide information about the port’s status. - If the port is open, it will be listed as “open” in the output.
- If the port is closed, it will be listed as “closed”.
Additionally, the output may include other details such as the service associated with the port and the version of the service.
How to Open Port in Linux
Opening ports in Linux involves configuring the firewall settings to allow incoming connections on specific ports. The exact method can vary depending on the firewall software used.
There are two common firewall solutions, they are given below.
Method 1: Opening Ports with iptables
- Open a terminal on your Linux system.
- Check if iptables installed by running the following command.
- sudo iptables –version
- If iptables not installed, you can typically install it using the package manager specific to your Linux distribution. (e.g., apt, yum, dnf).
- Determine the port number you want to open.
- Run the following command to add a rule.
- sudo iptables -A INPUT -p tcp –dport [port number] -j ACCEPT
- Replace [port number] with the actual port number you want to open.
- If you have IPv6 enabled and want to allow incoming connections on the same port for IPv6, run the following command.
- sudo ip6tables -A INPUT -p tcp –dport [port number] -j ACCEPT
- Save the iptables rules to persist across reboots.
- sudo iptables-save | sudo tee /etc/iptables/rules.v4
- sudo iptables-save | sudo tee /etc/iptables/rules.v6
- Consult your distribution’s documentation for the appropriate command if you are using a different distribution.
- The specified port is now open on your Linux system.
Method 2: Opening Ports with firewall
- Open a terminal on your Linux system.
- Check if firewall installed by running the following command
- sudo firewall-cmd –version
- Determine the port number you want to open.
- Run the following command to open the specified port.
- sudo firewall-cmd –add-port =[port number]/tcp –permanent
- Reload the firewall to apply the changes
- sudo firewall-cmd –reload
- The specified port is now open on your Linux system.
Also read: Switch Users in Linux Terminal using Su and Sudo Command
How to Open Ports in Ubuntu-based Systems
Opening ports in Ubuntu-based systems may done using the Uncomplicated Firewall (UFW), which provides a simplified interface for managing firewall rules.
Follow the steps below to open ports using UFW
- Open a terminal on your Ubuntu-based system.
- Check if UFW installed by running the following command
- sudo ufw –version
- If UFW not installed, you can install it using following command.
- sudo apt-get install ufw
- Enable UFW by running the command.
- sudo ufw enable
- You may prompted for your password.
- Determine the port number and protocol (TCP or UDP) you want to open.
- Run the following command.
- sudo ufw allow [port number]/[protocol]
- Replace [port number] with the actual port number you want to open, and [protocol] with either “tcp” or “udp” depending on the protocol you need.
- To open TCP port 80, the command would be:
- sudo ufw allow 80/tcp
- Repeat step 5 for any additional ports you want to open.
- Check the status of UFW to verify the changes.
- sudo ufw status
- The output will display the status of UFW and the list of rules including the newly added ones.
UFW will automatically configure the firewall to allow incoming connections on the specified ports. It manages the underlying firewall rules, making it easier to handle firewall configurations on Ubuntu-based systems.
How to Open Ports in Cent OS-based Systems
To open ports in CentOS-based systems, you can utilize the firewalld service, which is the default firewall management tool for CentOS. Following steps are useful to open ports using firewalld.
- Open a terminal on your CentOS-based system.
- Check if firewalld installed by running the following command
- sudo firewall-cmd –version
- Start the firewalld service by running the command.
- sudo systemctl start firewalld
- Enable the firewalld service to start automatically at boot time
- sudo systemctl enable firewalld
- Determine the port number and protocol (TCP or UDP) you want to open.
- Run the following command to add a rule
- sudo firewall-cmd –zone=public –add-port=[port number]/[protocol] –permanent
- Reload the firewalld configuration to apply the changes.
- sudo firewall-cmd –reload
- Verify the added rule and check the status of firewalld
- sudo firewall-cmd –list-all
- The output will display the list of active zones and the rules including the newly added one.
- Firewalld simplifies the process of managing firewall rules in CentOS-based systems.
Also Check: Sudo Command in Linux
How to Open Port in Other Linux Distributions
Opening ports in other Linux distributions typically involves configuring the firewall software used in the respective distribution. While the specific commands and tools may vary, the underlying principles remain similar. Below steps you can follow to open ports in other Linux distributions.
- Determine which firewall software used in your Linux distribution. Common firewall software includes iptables, nftables, firewalld, and ufw.
- Run the appropriate command to check firewall software installed on your system.
- Install the firewall software, if necessary.
- Once you have installed the firewall software, you can proceed to configure the firewall rules to open the desired ports.
- Verify the changes.
Note that the steps and commands provide here generalized, and the actual process may vary based on the Linux distribution and the firewall software used.
Can I open ports using a graphical interface in Linux?
Yes, many Linux distributions provide graphical tools or firewall management applications that allow users to open ports using a user-friendly interface.
What are the troubleshooting steps if I am unable to open a port in Linux?
If you encounter issues, troubleshooting steps include double-checking the firewall rules, ensuring the service or application is running and listening on the correct port, and verifying that there are no network restrictions or conflicts.
Is it recommended to open all ports on my Linux system?
No, it’s not recommended generally to open all ports on your Linux system.
Can I open ports temporarily in Linux?
Yes, you can open ports temporarily by configuring firewall rules.
