Port-knocking client (e.g. for knockd) in Python

knock.py

#!/usr/bin/env python3
# Port-knocking client
# Usage: knock HOST PORT [PORT...]

import socket
import sys

try:
  host = sys.argv[1]
  ports = [int(p) for p in sys.argv[2:]]
  ports[0]
except (ValueError, IndexError):
  print('Usage: %s HOST PORT [PORT...]' % sys.argv[0], file=sys.stderr)
  sys.exit(1)

TIMEOUT_SECS = 0.2

# Get IP address and address family
family, _, _, _, (ip, _) = socket.getaddrinfo(
    host, port=None, flags=socket.AI_ADDRCONFIG)[0]

for port in ports:
  s = socket.socket(family, socket.SOCK_STREAM)
  s.settimeout(TIMEOUT_SECS)
  s.connect_ex((ip, port))
  s.close()