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Check port in Windows and Linux

Check port in Windows and Linux

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Whether you’re troubleshooting network issues, setting up a server, or ensuring security compliance, check port state is an essential task for system administrators and developers alike. Ports are communication endpoints for networked devices, and knowing which ones are open can help you monitor traffic, detect vulnerabilities, or verify that services are running properly.

In this article, we’ll walk you through how to check open ports on both Windows and Linux systems. No matter your operating system or level of experience, these steps will equip you with the tools needed to manage and secure your network more effectively.

Check listening ports in Windows

To check listening ports in Windows, you can use several built-in tools. Here’s how:

Method 1: Using netstat Command

  • Open Command Prompt as Administrator:
    Press Win + X → choose Command Prompt (Admin) or Windows Terminal (Admin).
  • Run the following command: 
netstat -ano | findstr LISTENING
  • To find which program is using a specific port: 
tasklist /FI "PID eq <PID_NUMBER>"

Method 2: Using PowerShell

Run this command in PowerShell:

Get-NetTCPConnection -State Listen


You can also filter by port or local address:

Get-NetTCPConnection -State Listen | Where-Object { $_.LocalPort -eq 80 }

Method 3: Using Resource Monitor

  • Press Win + R, type resmon, and press Enter.
  • Go to the Network tab.
  • Under Listening Ports, you can see:
  • The port number
  • The process name
  • The PID

Check listening ports in Linux

To check listening ports in Linux, you can use various command-line tools depending on what’s installed. Here’s a list of the most common and effective methods:

Method 1: Using ss (modern and preferred)

ss -tuln
  • -t: TCP ports
  • -u: UDP ports
  • -l: Listening ports only
  • -n: Show numeric port numbers (skip DNS lookup)

To include the process using the port:

ss -tulnp

Method 2: Using netstat (older but still common)

Note: netstat may require installing net-tools on some systems.

netstat -tuln
  • Add -p to show the program name and PID:
netstat -tulnp

Method 3: Using lsof

sudo lsof -i -P -n | grep LISTEN
  • -i: Network files
  • -P: Show port numbers instead of service names
  • -n: Do not resolve hostnames
  • grep LISTEN: Filters for listening ports only

Check remote ports in Windows

To check if a remote port is open in Windows, you can use several built-in tools or third-party utilities. Here are the most effective methods.

Method 1: Using Test-NetConnection in PowerShell (Recommended)

This is the most modern and reliable method:

Test-NetConnection -ComputerName <hostname_or_ip> -Port <port_number>

Example:

Test-NetConnection -ComputerName example.com -Port 80
  • Shows if the port is reachable
  • Provides ping status, TCP connection, and more

Method 2: Using Portqry Tool from Microsoft

Download from Microsoft: PortQry Command Line Port Scanner

Basic usage:

portqry -n <hostname_or_ip> -p tcp -e <port_number>

Example:

portqry -n 192.168.1.100 -p tcp -e 3389

Gives detailed results like:

  • Listening
  • Not listening
  • Filtered

Check remote ports in Linux

To check if a remote port is open in Linux, you can use several command-line tools depending on what’s available on your system. Below are the most common and effective methods.

Method 1: Using nc (Netcat) for check port

nc -zv <hostname_or_ip> <port>
  • -z: Zero-I/O mode (scan without sending data)
  • -v: Verbose output

Example:

nc -zv example.com 443

✅ If the port is open, it will return:
Connection to example.com 443 port [tcp/https] succeeded!

❌ If closed, you’ll see a connection refused or timed out message.

Method 2: Using nmap (Advanced and powerful)

nmap -p <port> <hostname_or_ip>

Example:

nmap -p 22 192.168.1.1

You can scan multiple ports or ranges:

map -p 22,80,443 example.com

Or scan all 65,535 TCP ports:

nmap -p- example.com

Method 3: Using timeout with bash built-ins (No extra tools)

timeout 3 bash -c "</dev/tcp/<hostname_or_ip>/<port>" && echo "Open" || echo "Closed"

Example:

timeout 3 bash -c "</dev/tcp/example.com/22" && echo "Open" || echo "Closed"

Conclusion

Being able to check port state —both locally and remotely—is a fundamental skill for anyone managing systems or troubleshooting network issues. Whether you’re using Windows or Linux, there are reliable built-in tools and optional utilities that allow you to verify which ports are listening and whether a remote service is reachable.

On the local side, commands like netstat, ss, and lsof help identify active ports and their associated processes. For remote checks, tools such as Test-NetConnection, nc, and nmap make it easy to test connectivity and detect potential firewalls or configuration issues.

By mastering these methods, you can better secure your systems, ensure services are functioning correctly, and quickly diagnose connection problems. Whether you’re working on a personal project or maintaining enterprise infrastructure, these port-checking techniques are essential parts of your network toolbox.

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