As I embark on my cybersecurity journey, I’ve decided to document everything I learn. You can check out my previous blog here.

Creating Python Firewall

Today, I started working on a home firewall in Python to learn about sockets, networking, and how programs interact with the OSI model. I began by exploring Python’s socket module to create a basic client-server communication system.

What I Built

1. A custom Python server using sockets
   
   
2. A manual Python client to send requests to the server
   
   
3. Implemented basic data exchange between client and server.
   
   

Key Learnings

✅ How to create and bind a socket to a port
✅ How to listen for incoming connections
✅ Handling concurrent connections using socket.listen()
✅ Sending and receiving data between client and server
✅ Understanding raw sockets and how they work
✅ Debugging network issues using netstat

Debugging Lessons

While running multiple tests, I encountered an issue where my server wouldn’t restart😅. Turns out, the port was already in use due to previous runs 😁. I learned to use netstat to find and kill processes blocking my port.😎

MY BAD

Breaking Down My Code:

Server Side (server.py)

1️⃣ Import the socket module:

import socket

2️⃣ Create a socket:

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

• AF_INET → IPv4 addressing
• SOCK_STREAM → TCP connection (alternative: SOCK_DGRAM for UDP)

3️⃣ Bind the socket to an IP and port:

sock.bind(("0.0.0.0", 8080))

4️⃣ Start listening for connections:

sock.listen(5) 

5️⃣ Accept incoming connections:

conn, client_IP = sock.accept()

6️⃣ Send data to the client:

conn.send("Hello, this is the server".encode("utf-8"))

7️⃣ Close the connection:

conn.close()

Client Side (client.py)

1️⃣ Create a client socket:

sock = socket.socket()

2️⃣ Connect to the server:

sock.connect(("SERVER_IP", 8080))

3️⃣ Receive server response:

data = sock.recv(2048)
print(data.decode("utf-8"))

4️⃣ Close the client connection:

sock.close()

Final Thoughts:

This might not seem like a big achievement, but for me, it’s a step closer to my dream: becoming a Security Engineer. Every small step matters!

Here is a little reference if you want to:

• Medium Article

Soon i will upload my progress on github for cleaner documentation.

Looking forward to continuing this journey—see you in the next blog! 🚀

Happy Programming, Happy Hacking🧑‍💻