How to optimize port-scanning with a multi-threaded approach

Introduction
Python port-scanning example
Conclusion

Introduction

Port scanning is regularly used in the vulnerability analysis of servers. Although port scanning is quite simple - this multi-threaded approach can be repurposed for other more valuable use-cases, eg. API testing. The purpose of this approach is to optimize the application, reducing the execution time significantly.

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Python port-scanning example

Full example code found below:


import socket, threading

host = raw_input("Enter an address to scan: ")
ip = socket.gethostbyname(host)
threads = []
open_ports = {}

def try_port(ip, port, delay, open_ports):

    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) #socket.AF_INET, socket.SOCK_STREAM
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    sock.settimeout(delay)
    result = sock.connect_ex((ip, port))

    if result == 0:
        open_ports[port] = 'open'
        return True
    else:
        open_ports[port] = 'closed'
        return None

def scan_ports(ip, delay):

def scan_ports(ip, delay):

    for port in range(0, 1023):
        thread = threading.Thread(target=try_port, args=(ip, port, delay, open_ports))
        threads.append(thread)

    for i in range(0, 1023):
        threads[i].start()

    for i in range(0, 1023):
        threads[i].join()

    for i in range (0, 1023):
        if open_ports[i] == 'open':
            print '\nport number ' + str(i) + ' is open'
        if i == 1022:
            print '\nscan complete!'

if __name__ == "__main__":
    scan_ports(ip, 3)