Python port scanner exception problems

Question

import socket
import sys
import threading
import concurrent.futures
import pyfiglet,time
import colorama
from colorama import Fore

ascii_banner = pyfiglet.figlet_format("Port Scanner")
print(ascii_banner)

print(Fore.GREEN + "Stat time: " + time.asctime())
start = time.perf_counter()

my_file = open("List of OpenPorts.txt", "w")
my_file.write("Port Scanner \n\n")


colorama.init()

print_lock = threading.Lock()

ip = input(Fore.BLUE + "Enter the IP to scan: ")

def scan(ip, port):
    scanner = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    scanner.settimeout(1)
    try:
        scanner.connect((ip, port))
        scanner.close()
        with print_lock:
            print(Fore.BLUE + f"Port[{port}]" + Fore.GREEN + " Opened")
            my_file.write(f'Port{port} is open \n')
    except socket.gaierror:
        print("Invalid Hostname. Please enter in a valid hostname")
        my_file.write("Invalid Hostname. Please enter in a valid hostname")




with concurrent.futures.ThreadPoolExecutor(max_workers=100) as executor:
    for port in range(1025):
        executor.submit(scan, ip, port + 1)

finish = time.perf_counter()
print("End time: " +time.asctime())
print(f'Finished in {round(finish - start, 2)} second(s)')
my_file.close()

**Im trying to make the code print only one exception when it encounters a problem. But when the code runs it prints the error code multiple times , I'm guessing it prints it 1025 times because of the threading code . Im not sure how to make it print only one time and end the code afterwards. **

Answer 1

Because every thread is checking for the same error (invalid hostname), if we run scan() once with a random port number we can check for the invalid hostname before spinning up all 1025 threads.

import socket
import sys
import threading
import concurrent.futures
import pyfiglet,time
import colorama
from colorama import Fore

ascii_banner = pyfiglet.figlet_format("Port Scanner")
print(ascii_banner)

print(Fore.GREEN + "Stat time: " + time.asctime())
start = time.perf_counter()

my_file = open("List of OpenPorts.txt", "w")
my_file.write("Port Scanner \n\n")


colorama.init()

print_lock = threading.Lock()

ip = input(Fore.BLUE + "Enter the IP to scan: ")

def scan(ip, port):
    scanner = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    scanner.settimeout(1)
    try:
        scanner.connect((ip, port))
        scanner.close()
        with print_lock:
            print(Fore.BLUE + f"Port[{port}]" + Fore.GREEN + " Opened")
            my_file.write(f'Port{port} is open \n')
    except socket.gaierror:
        with print_lock:
            print("Invalid Hostname. Please enter in a valid hostname")
            my_file.write("Invalid Hostname. Please enter in a valid hostname")
            return False
    except ConnectionRefusedError:
        pass

    return True



with concurrent.futures.ThreadPoolExecutor(max_workers=100) as executor:
    # Random value
    if not scan(ip, 10000):
        exit(0)

    for port in range(1025):
        executor.submit(scan, ip, port + 1)

finish = time.perf_counter()
print("End time: " +time.asctime())
print(f'Finished in {round(finish - start, 2)} second(s)')
my_file.close()