Python Port Scanner (Educational)
Goal: understand TCP connect behavior + timeouts using Python sockets (authorized environments only).
Overview
This writeup documents a small script that attempts TCP connections to a list of ports and reports which ones accept connections.
Python
Networking
What I learned
• connect_ex returns 0 on success
• timeouts matter for speed & accuracy
• basic error handling and clean loops
port_scan.py
import socket
def scan(host: str, ports: range, timeout: float = 0.4) -> list[int]:
open_ports = []
for port in ports:
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.settimeout(timeout)
if s.connect_ex((host, port)) == 0:
open_ports.append(port)
return open_ports
if __name__ == "__main__":
# Use only on systems you own or have explicit permission to test.
target = "127.0.0.1"
ports = range(1, 1025)
result = scan(target, ports)
print("Target:", target)
print("Open ports:", result if result else "None")Ethics note
This is for learning. Don’t scan networks or systems you don’t own / don’t have explicit authorization to test.