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.
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
Download v2.00
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