Network interface ports are critical for communication between systems over a network. In Linux, understanding how network ports function can help you troubleshoot connection issues and manage your server more effectively. This guide will explore the basics of network interface ports in Linux and how to manage them on a VPS or local server.

What is a Network Interface Port?

A network interface port is a logical endpoint for communication. Ports are used by the Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) to differentiate between different types of network traffic. For example, web traffic typically uses port 80 for HTTP and port 443 for HTTPS, while SSH traffic uses port 22.

Viewing Open Ports in Linux

To view the open ports on your Linux system, you can use the netstat or ss command. This will show you which services are listening on specific ports. For example, to list all listening ports, you can run the following command in your terminal:

sudo ss -tuln

This command shows both TCP (-t) and UDP (-u) ports that are actively listening (-l), along with their numeric port numbers (-n).

Commonly Used Ports in Linux

Here are some commonly used ports in Linux:

• SSH (22): Secure Shell access to remote machines, commonly used for managing servers such as a VPS server.
• HTTP (80): Unencrypted web traffic.
• HTTPS (443): Secure web traffic with encryption.
• FTP (21): File Transfer Protocol for transferring files.
• MySQL (3306): Database server communication.

Managing Ports with UFW (Uncomplicated Firewall)

If you're managing a VPS server and need to allow or block certain ports, the UFW (Uncomplicated Firewall) tool is easy to use. For example, to allow SSH access on port 22, you can run the following command:

sudo ufw allow 22/tcp

Similarly, to allow HTTP traffic on port 80, use:

sudo ufw allow 80/tcp

Once you've configured your ports, make sure UFW is enabled:

sudo ufw enable

Changing Default Ports

For security reasons, many administrators choose to change default ports on their VPS servers. For example, changing the default SSH port (22) can help reduce the risk of brute-force attacks. To change the SSH port, edit the SSH configuration file:

sudo nano /etc/ssh/sshd_config

Find the line that reads #Port 22 and change it to another port number, such as:

Port 2222

After saving your changes, restart the SSH service:

sudo systemctl restart ssh

Network Interface Ports on a VPS

On a VPS server, managing network interface ports is essential for controlling traffic flow and ensuring security. If you're running services like web servers, databases, or SSH on your VPS, configuring the appropriate ports will help you manage access and ensure that only authorized traffic reaches your server.

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