Python open port scanner

portscan.py

#!/usr/bin/env python3
import socket
import sys
import threading

HOST = sys.argv[1]
SERVER = socket.gethostbyname(HOST)
print(F"[*] Port Scanning on {SERVER}")
def scan(start,end):
	for PORT in range(start,end):
		with socket.socket(socket.AF_INET) as s:
			ret = s.connect_ex((SERVER,PORT))
			if ret == 0:
				print(F"[+] TCP port {PORT} is opened!")

scan(0,65536)
print(F"[+] Scanning completed on host {SERVER}")