Local Port Scout

What it does

Local Port Scout checks a local or private host for open TCP ports. It is intentionally scoped for safe lab use and local network learning.

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How it works

1. IP Address & Ports: A computer has one IP address (like a street address) but thousands of ports (like apartment numbers). Websites listen on port 80/443, email on port 25, etc.
2. The Handshake (TCP): The script uses Python's standard socket library to attempt a quick connection to a port. This is called a TCP Three-Way Handshake.
3. The Result:
   • If the connection succeeds, the script prints that the port is OPEN.
   • If the connection times out or is refused, the port is CLOSED.
4. Multithreading: Instead of checking doors one by one (which takes a long time), the script spawns multiple "workers" (threads) to check many doors at the same time.

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Implementation notes

• socket.socket(socket.AF_INET, socket.SOCK_STREAM): Creates a new network socket using IPv4 and TCP.
• s.connect_ex((host, port)): Attempts to connect. Unlike connect(), which crashes the script if it fails, connect_ex returns a status number. A value of 0 means success (port is open).
• threading.Thread(...): Runs the scanner logic concurrently, scanning hundreds of ports per second.

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Running it

Run the scanner against a local or private host:

python port_scanner.py

Note: For safety, This script is restricted to scanning local hosts (like localhost or 127.0.0.1) to prevent accidental scanning of remote systems.