knock.py

import socket
import sys

socket.setdefaulttimeout(0.1)

for p in sys.argv[2:]:
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    try:
        print("Connecting to %s:%d" % ((sys.argv[1], int(p))))
        s.connect((sys.argv[1], int(p)))
    except:
        s.close()

knock.sh

domain=$1
shift
# for p in ${@:2}; do 
for p in $@; do 
	nmap -Pn --max-retries 0 -p $p $domain; 
done