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A Network Debugging Tool That Works for You
Need to verify that a port is open and reachable on your Windows machine? Whether you are troubleshooting a firewall rule, confirming that a service is listening, or testing connectivity between applications, Port Listener gives you instant, real-time feedback without complex configuration or heavyweight network analyzers.
Originally developed to test error conditions in our own software, Port Listener has grown into a fully featured TCP port monitoring utility trusted by developers, system administrators, and security professionals. Version 2.00 is a complete rewrite from the ground up -- now with live TCP/IP connection monitoring, built-in HTTP response handling, system tray support, and timestamped logging.
Simply specify a port, click Start Listening, and watch connections arrive in real time. Port Listener automatically detects whether incoming traffic is an HTTP request and responds with valid HTML, or sends a plain-text welcome message for raw TCP connections. Run multiple instances simultaneously to monitor several ports at once -- each one runs independently.
Who Is This For?
- Developers -- Test network communication between applications, verify API endpoints are reachable, and debug client-server connections without deploying full services.
- Network administrators -- Troubleshoot connectivity issues, confirm port availability through firewalls, and validate load balancer configurations.
- Security analysts -- Analyze incoming data for security testing, inspect raw packet contents, and verify firewall rules are working as expected.
- General users -- Quickly check if a specific port is blocked or accessible on your machine without needing deep networking knowledge.
Key Features
TCP Port Listening
Instantly listen on any specified TCP port. Port Listener binds to the port and waits for incoming connections, giving you immediate visibility into network traffic.
Live Connection Monitoring
See which remote hosts are connecting in real time. View source IP addresses, connection timestamps, and incoming data as it arrives -- no packet sniffer required.
Built-In HTTP Response
Port Listener automatically detects HTTP requests and responds with a valid HTML page, confirming that your port is reachable from browsers, Postman, curl, or any HTTP client.
Multiple Instances
Run several Port Listener instances simultaneously to monitor multiple ports at once. Each instance operates independently with its own log and connection display.
System Tray Mode
Minimize Port Listener to the Windows system tray to keep your workspace clean while monitoring runs in the background. Hover for status, right-click for options.
Timestamped Logging
Enable timestamps in the log to track exactly when each connection arrives. Optional log clearing on each restart keeps output focused on the current session.
Fully Portable -- Zero Installation
No Installation Required Runs directly from an .exe file. No setup wizard, no "Next, Next, Finish."
Runs From USB Copy to a flash drive and use on any PC. IT techs carry these on a keychain for on-site support.
Leaves No Trace No files left behind after use. Delete the folder and it is gone completely.
No Registry Changes Does not modify the Windows registry, system settings, or install drivers.
Self-Contained Everything the program needs lives in its own folder. No scattered DLLs or AppData clutter.
No Admin Rights Needed Runs under standard user accounts. No UAC prompts, no IT ticket required.
Lightweight Tiny footprint, typically under 1 MB. No frameworks, runtimes, or bloated dependencies.
Instant Startup Launches in under a second. No splash screens, no loading bars, no waiting.
How to Get Started
- Extract and launch -- Unzip the download and run
listener.exe. No installation required.
- Choose a port -- Enter any TCP port number and click Start Listening.
- Allow firewall access -- When Windows Firewall prompts you, allow both public and private network access for Port Listener.
- Test connectivity -- Connect from a browser, telnet, PowerShell, Postman, or any other tool. Port Listener will display the connection and respond automatically.
Command Line Options
Pass a port number on the command line to auto-start listening and minimize to the system tray:
listener.exe [port number]
Sample Responses
HTTP Request -- When Port Listener detects an HTTP request, it responds with a valid HTML page:
HTTP/1.1 200 OK
Content-Type: text/html; charset=UTF-8
<html>
<head><title>Port Listener v2.00</title></head>
<body>
<h2>Port Listener is working!</h2>
</body>
</html>
Raw TCP (Telnet) -- Plain text response for non-HTTP connections:
Welcome to the Port Listener Server on port [portnumber]
Port Listener v2.00 - Windows Support
Win 11
Win 10
Win 8
Win 7
Server 2022
Server 2019
Server 2012
Server 2011
Server 2008 R2
Port Listener v1.03 - Legacy Windows Support
Version 1.03 has reached end of life but remains available for older Windows systems.
Vista
XP
ME
98
95
Server 2003
Server 2000
NT Server
Download Port Listener
Screenshots
The main screen lets you specify a TCP port to listen on. Click Start Listening to begin monitoring incoming connections.
Port Listener detects HTTP requests and responds with a valid HTML page, confirming that your port is reachable from any browser.
Telnet and raw TCP connections receive a plain-text welcome message confirming connectivity on the specified port.
Using Postman to make an HTTP request -- Port Listener detects the request type and responds with the appropriate HTML.
A PowerShell script creates a TCP connection to Port Listener, which receives the message and sends back a plain-text response.
When you first minimize Port Listener, a balloon hint explains how to interact with the app from the Windows taskbar.
Hover over the system tray icon to see the current listening status and port number.
Right-click the tray icon for quick access to restore, stop listening, or exit the application.
If the port you selected is already in use by another application, Port Listener will display an error message so you can choose a different port.
Always allow both public and private network access when Windows Firewall prompts you, otherwise Port Listener cannot receive connections.
A complete walkthrough: listening on port 8080, opening Firefox to localhost:8080, and seeing the HTTP response and raw headers in Port Listener.
Version History
v2.00
April 6, 2025
Complete rewrite of the software from the ground up.
This version only supports Windows 7, 8, 10, 11 and Windows Server 2008, 2011, 2012, 2019, 2022 and newer.
Removed UDP support (did not work on newer Windows versions).
Added detection of HTTP requests with valid HTML response.
Raw TCP sockets now send a welcome message when a client connects.
Added option to include timestamps in the log.
Added option to clear the log each time listening starts.
Added Windows System Tray support.
Command-line port number now auto-minimizes and starts listening.
Corrected min and max port numbers for new Windows restrictions.
v1.03
July 21, 2016
Added a command-line option to pass in the port number.
v1.02
June 25, 2015
Added a connection type of TCP or UDP.
Defaulted to TCP.
Minor spelling corrections.
v1.01
October 31, 2007
Added Port Data View to see incoming data on the port.
Increased ports to 999999.
Enhanced error handling for exceptions.
Corrected issues with the tray icon restore state.
What Users Are Saying
★★★★★
"Indispensable for firewall testing. Drop it on a server, listen on a port, test from the other side."
-- Jason K., Network Engineer
★★★★★
"The HTTP reachability testing is great. I use it daily to verify connectivity between services."
-- Laura D., DevOps Engineer
Download Port Listener
What's New in v2.00: Added HTTP reachability testing, Redesigned interface, Added Always On Top and system tray
Windows 11, 10, 8, 7 · Server 2022, 2019, 2012, 2011, 2008 R2 · 321 KB
1.2 MB
SHA256: 6b292df48590...b764
Freeware
Updated: April 6, 2025
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Support Port Listener Development
Port Listener is completely free. If this tool has saved you time or simplified your network troubleshooting, consider making a donation to help fund continued development and new features.
Support and Information
Frequently Asked Questions
Find answers to common questions about Port Listener.
View FAQ
Need Help?
Found a bug or have a question? We are here to help.
Contact Us
Uninstall
To uninstall, simply delete the program folder. No registry entries or system files are left behind.
How to Update
Download the latest version and extract over your existing folder, or to a new location. Settings are preserved.
Privacy: This software does not collect, transmit, or store any personal data. No internet connection required.
End-User License Agreement (EULA)
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