---
title: "How to Read netstat and ss Output: A Guide"
url: "https://astraguardvpn.com/blog/how-to-read-netstat-and-ss-output-a-guide"
description: "Learn to interpret netstat and ss outputs, including LISTEN and ESTABLISHED states, with examples and troubleshooting tips."
updated: "2026-08-24T09:00:15.991Z"
---

# How to Read netstat and ss Output: A Guide

Understand netstat and ss outputs with examples and technical depth. Learn to identify listening ports and processes.

Before You Start Understanding network connections is crucial for troubleshooting and optimizing systems. This guide will help you interpret network socket states using two popular tools: netstat and ss. Before diving in, ensure you have administrative access on your system to run these commands. Technical Background Network sockets are endpoints for sending or receiving data across a computer network. They use the Internet Protocol (IP) suite to communicate, often appearing as listening or established connections. A socket in the LISTEN state is waiting for incoming connections, much like a receptionist waiting for a phone call. An ESTABLISHED state indicates an active, two-way communication channel between sockets. The netstat (network statistics) and ss (socket statistics) commands provide insights into these network connections. Netstat is older and widely used, while ss is a newer tool offering similar functionality with enhanced capabilities and performance. Both tools can reveal which process owns a port, crucial for diagnosing network issues or security threats. Step By Step 1. Identify Your Operating System: - For Windows, use PowerShell. - For Linux or macOS, use a Terminal. 2. Check Listening Ports: - Windows: Open PowerShell and type `netstat -an | findstr LISTEN`. - Linux/macOS: Open Terminal and run `sudo netstat -tuln`. 3. Determine Established Connections: - Use `netstat -an | findstr ESTABLISHED` in PowerShell. - Use `sudo netstat -tan | grep ESTABLISHED` in Terminal. 4. Find Process Owning a Port: - Windows: `netstat -ano | findstr :PORT_NUMBER`. Replace PORT_NUMBER with the actual port. - Linux/macOS: `sudo lsof -i :PORT_NUMBER`. Worked Example Example: Checking Listening Ports on Linux Command: sudo ss -tuln Output: Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port tcp LISTEN 0 128 0.0.0.0:22 0.0.0.0:* tcp LISTEN 0 128 127.0.0.1:631 0.0.0.0:* This output shows two services: SSH (port 22) and CUPS (port 631) listening for incoming connections. Configuration Or Command Reference - `-t` or `--tcp`: Display TCP sockets. - `-u` or `--udp`: Display UDP sockets. - `-l` or `--listening`: Show only listening sockets. - `-n`: Show numerical addresses instead of resolving hostnames. - `-p` or `--processes`: Show the process using the socket (root privileges required). Troubleshooting Symptom: No output from netstat or ss. Likely Cause: Insufficient privileges. Fix: Run the command with `sudo` or as an administrator. Symptom: Unknown port in LISTEN state. Likely Cause: Unwanted or rogue process. Fix: Identify the process with `-p` flag and terminate if necessary. Symptom: High number of ESTABLISHED connections. Likely Cause: Network congestion or attack. Fix: Review and optimize network configuration; consider security assessments. Related Concepts And Further Reading - TCP/IP Protocol Suite - Network Security Basics - Process Management and Monitoring - Linux Networking Tools - Windows Networking Commands Key Takeaways • Network sockets facilitate communication between devices. • LISTEN state indicates a socket is waiting for connections. • ESTABLISHED state represents active communication. • netstat and ss are powerful tools for network diagnostics. • Identifying processes that own ports can enhance security. FAQ Q: What is the difference between netstat and ss? A: ss is a newer tool with enhanced performance and capabilities compared to netstat. Q: Can I find which process owns a port on Windows? A: Yes, use `netstat -ano` and cross-reference the PID with Task Manager. Q: Why do I need administrative privileges to run these commands? A: Accessing network sockets and process information requires elevated permissions for security reasons.

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