port_scanner.py in Python

Scan a host for open ports from a common list.

"""Scan a host for open TCP ports from a small common list."""
import socket
import sys

COMMON = {22: "ssh", 80: "http", 443: "https", 5432: "postgres",
          6379: "redis", 8080: "http-alt"}


def is_open(host, port, timeout=0.5):
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
        sock.settimeout(timeout)
        return sock.connect_ex((host, port)) == 0


def main():
    host = sys.argv[1] if len(sys.argv) > 1 else "127.0.0.1"
    print(f"scanning {host}")
    found = 0
    for port, name in sorted(COMMON.items()):
        if is_open(host, port):
            print(f"  {port:5d} open   ({name})")
            found += 1
    print(f"{found} of {len(COMMON)} common ports open")


if __name__ == "__main__":
    main()

How it works

1. connect_ex reports whether a port accepts.
2. A short timeout keeps closed ports fast.
3. Open ports are matched to service names.

Keywords and builtins used here

• as
• def
• else
• for
• if
• is_open
• len
• main
• print
• return
• sorted
• with

The run, in numbers

Lines

27

Characters to type

668

Tokens

199

Three-star pace

110 tpm

At the three-star pace of 110 tokens a minute, this run takes about 109 seconds.

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Step 1 of 3 in Encore, step 39 of 41 in Domain tools.

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