Name: Port Listener
Brand: RJL Software
Availability: InStock
Rating: 4.7 (4901 reviews)
Author: RJL Software

Port Listener - Lightweight TCP/IP Port Monitoring Tool

Port Listener v2.00 is a free, lightweight utility designed to listen on specified TCP ports, helping you troubleshoot network connections, detect port activity, and analyze incoming data. New in version 2.00, the tool now supports real-time visibility of TCP/IP connections and can even respond to incoming HTTP requests with an HTML response--great for confirming remote reachability. Whether you're a developer, sysadmin, or security analyst, Port Listener is a must-have for your toolkit.

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Key Features:

TCP Port Listening – Instantly listen on any specified TCP port.
New! View Live TCP/IP Connections – See which remote hosts are connecting in real time.
New! Built-In HTTP Response – Sends an HTML reply to incoming HTTP requests to confirm reachability.
Real-Time Data Display – Monitor incoming data as it arrives.
Multiple Instances Supported – Monitor several ports at once.
System Tray Mode – Keeps your workspace tidy while running in the background.

Perfect For:

Developers & IT Professionals - Test network communication between applications.
Network Administrators - Troubleshoot connectivity issues and confirm port availability.
Cybersecurity Analysts - Analyze incoming data for security testing and packet inspection.
General Users - Easily check if a port is blocked or accessible.

How It Works:

Launch Port Listener and specify a TCP port to listen on.
Minimize the application to the system tray for background monitoring.
View real-time data transmissions to analyze network traffic.
Run multiple instances to test multiple ports simultaneously.

Sample HTTP Response

Analyzes if the request looks like an HTTP request, simple response of an html page.

More detailed example can be found in our Screenshots

    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>

Sample telnet Response

Plain text, no headers, raw data sent back from Port Listener.

More detailed example can be found in our Screenshots

    Welcome to the Port Listener Server on port [portnumber]

Command line options explained for Port Listener:

You can send the port number along the command line to start lisening on that TCP port when the software starts.

listener.exe [port number]

Not sure what a command line is or how to use it? See our Support FAQ

Why Choose Port Listener?

Originally developed to test error conditions in our own software, we realized this tool could be incredibly useful for others as well. Now, we're offering Port Listener for free to help developers, IT teams, and security professionals simplify network troubleshooting.