portfinder.py

import argparse
import socket
import sys

Version = "1.0"

parser = argparse.ArgumentParser()
parser.add_argument("host", action="store", help="The host to test")
parser.add_argument("-r", action="store", dest="range", help="A range of ports to scan speperated by a -, for example: -r 125-150")
parser.add_argument("--version", action="version", version="%(prog)s {}".format(Version))
results = parser.parse_args()

popular = [21, 22, 23, 25, 53, 67, 68, 69, 80, 110, 123, 135, 137, 138, 139,
           143, 161, 162, 179, 389, 443, 445, 636, 989, 990]

s = socket.socket()
host = results.host
p_range = results.range

def attempt_connection(inp_host, inp_port):
    try:
        s.connect((inp_host, inp_port))
    except (ConnectionRefusedError, OSError):
        print("Port {} : Connection failed".format(inp_port))
    else:
        print("Port {} is open".format(inp_port))

if p_range == None:
    print("Checking popular ports on {}".format(host))
    for port in popular:
        attempt_connection(host, port)
else:
    try:
        start, finish = p_range.split("-", 1)
        int(start)
        int(finish)
        if finish <= start:
            raise ValueError
    except ValueError:
        print("range does not contain legal values")
    else:
        print("Checking ports {} to {} on host {}".format(start, finish, host))
        for port in range(int(start), int(finish)+1):
            attempt_connection(host, port)