Port Scan Localhost Common Ports in Python

Scan common localhost ports (HTTP, HTTPS, SSH, FTP, and more) with a fast socket-based Python script that prints an open/closed status table.

Easy Python 3.9+ Aug 9, 2026 Automation & scripting 13 views 0 copies

socket port-scanning network localhost automation

Python code

33 lines

Python 3.9+

import socket
from datetime import datetime

COMMON_PORTS = {
    80: "HTTP", 
    443: "HTTPS", 
    22: "SSH", 
    21: "FTP", 
    25: "SMTP",
    3306: "MySQL",
    5432: "PostgreSQL"
}

def scan_port(port):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.settimeout(0.1)
    try:
        result = sock.connect_ex(("127.0.0.1", port))
        return result == 0
    finally:
        sock.close()

def main():
    print(f"Port scan started at {datetime.now().strftime('%Y-%m-%d %H:%M:%S')}")
    print(f"{'Port':<8} {'Service':<12} {'Status':<10}")
    print("-" * 34)
    
    for port, service in sorted(COMMON_PORTS.items()):
        status = "OPEN" if scan_port(port) else "closed"
        print(f"{port:<8} {service:<12} {status:<10}")

if __name__ == "__main__":
    main()

Output

stdout

Port scan started at 2025-07-24 14:32:05
Port     Service      Status    
----------------------------------
21       FTP          closed    
22       SSH          closed    
25       SMTP         closed    
80       HTTP         open      
443      HTTPS        open      
3306     MySQL        closed    
5432     PostgreSQL   closed

How it works

This script uses socket.connect_ex() to test TCP connectivity without raising exceptions—it returns 0 when the port is open. The settimeout(0.1) makes the scan fast by capping how long each connection attempt waits. The finally block guarantees the socket closes even if an error occurs. The script prints results in a formatted table using f-strings, sorted by port number for readability.

Common mistakes

Forgetting to close the socket, which leaks file descriptors
Using `connect()` instead of `connect_ex()`, which throws exceptions on closed ports
Scanning public IPs without permission—this script is for localhost only
Setting too long a timeout, making the scan slow

Variations

Use `sock.timeout = 0.01` for faster scans with less accuracy
Replace `127.0.0.1` with a variable to scan remote hosts

Real-world use cases

Checking which dev services are running locally before starting a project.
Verifying firewall rules by confirming which ports are open on a test server.
Monitoring a local machine for unexpected open ports as a basic security check.

Port Scan Localhost Common Ports in Python

Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

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Common mistakes

Variations

Real-world use cases

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