DEV Community

Radosław
Radosław

Posted on

Building NETRadar - My First Real Network Scanner in Python

#python #programming #software #beginners

Building NetRadar – My First Real Network Scanner in Python

Instead of doing another tutorial project, I decided to build something that actually works in a real environment.

That’s how NetRadar came to life — a simple CLI tool for scanning local networks and detecting open ports.

💡 Why I built it

I didn’t want to just follow guides anymore.
I wanted to understand how networking actually works — not just in theory, but in practice.

So the idea was simple:

Scan a local network → find active devices → check which ports are open.

At first, it sounded straightforward.
In reality, it turned into a much more interesting challenge.

🔧 What NetRadar does

NetRadar is a CLI-based tool that allows you to:

  • discover active hosts in a local network
  • scan TCP ports (quick / deep modes)
  • detect open ports using sockets
  • map ports to known services (HTTP, SSH, RDP, etc.)
  • validate user input (IP ranges, modes, etc.)
  • export results to a structured JSON file
  • display clean, readable output in the terminal

🖥️ Example output 

======= RESULTS =======

Host: 192.168.0.1
  80 (HTTP)
  443 (HTTPS)

Host: 192.168.0.5
  No open ports

======= SUMMARY =======
Active hosts: 2
Open ports found: 2
Enter fullscreen mode Exit fullscreen mode

📁 JSON output

One of the things I focused on was making the output usable, not just visible.

{
  "scan_info": {
    "base": "192.168.0.",
    "range": "192.168.0.1-192.168.0.10",
    "mode": "quick",
    "timestamp": "2026-04-12 20:15:33"
  },
  "results": [
    {
      "ip": "192.168.0.1",
      "open_ports": [
        { "port": 80, "service": "HTTP" }
      ]
    }
  ]
}
Enter fullscreen mode Exit fullscreen mode

⚙️ How it works (simplified)

1. Host discovery

I used subprocess to ping IP addresses:

ping -n 1 192.168.0.x
Enter fullscreen mode Exit fullscreen mode

If the response is successful → the host is active.

2. Port scanning

This was the most interesting part.

I used Python sockets:

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.settimeout(0.5)
result = sock.connect_ex((host_ip, port))
Enter fullscreen mode Exit fullscreen mode

If result == 0, the port is open.

3. Data structure

Instead of just printing results, I stored everything in dictionaries:

{
  "ip": "192.168.0.1",
  "active": True,
  "open_ports": [
    {"port": 80, "service": "HTTP"}
  ]
}
Enter fullscreen mode Exit fullscreen mode

This made it easy to:

  • print results
  • export to JSON
  • extend the project later

🧠 What I learned

This project taught me a lot more than I expected:

  • how socket connections actually work
  • how to design clean and usable data structures
  • how to handle user input properly
  • how to turn logic into a real CLI tool
  • how small UX details (like output formatting) matter

The biggest difference compared to tutorials was this:

I had to solve real problems on my own.

🚀 Challenges

Some things were harder than I thought:

  • handling invalid user input
  • structuring the data cleanly
  • making the output readable
  • debugging network behavior

At one point, nothing worked and I had no idea why —
but fixing those issues was the most valuable part.

🔥 What’s next (NetRadar V2)

I’m already working on improvements:

  • multi-threading (faster scanning)
  • better performance
  • more advanced features
  • possibly a simple GUI

🧭 Final thoughts

This is not a huge project, but it’s the first one that actually feels like a real tool, not just an exercise.

And that changed the way I approach learning.

Instead of just consuming content, I’m trying to build things that:

  • solve real problems
  • can be improved over time
  • actually work outside of tutorials

If you have any feedback or ideas — I’d love to hear them 👇

Top comments (0)