Port scanner using multithreading

Question

I have written a rather simple port scanner using Python, and I would like to know things I could do better regarding:

• Code quality, making the code in general better

• Performance, making the code run faster and more efficient

• Making the scan more lightweight for the system being scanned so there is no risk of it crashing

At the moment it takes around 160 seconds to scan all ports.

import socket
import time
import threading
from queue import Queue
socket.setdefaulttimeout(0.25)
print_lock = threading.Lock()
target = '127.0.0.1'
def portscan(port):
 s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
 try:
 con = s.connect((target, port))
 with print_lock:
 print('Port', port, 'is open!')
 con.close()
 except:
 pass
def threader():
 while True:
 worker = q.get()
 portscan(worker)
 q.task_done()
q = Queue()
startTime = time.time()
for x in range(100):
 t = threading.Thread(target=threader)
 t.daemon = True
 t.start()
for worker in range(1, 65536):
 q.put(worker)
q.join()
print('Time taken:', time.time() - startTime)

• hjpotter92: just putting it out there stackoverflow.com/a/16780297/1190388

Answer 1

The review only addresses this aspect:

Code quality, making the code in general better

Naming

The PEP 8 style guide recommends snake_case for function and variable names.

Function portscan would be better as port_scan.

Variable startTime as start_time.

It also recommends all upper case letters for constants:

TARGET = '127.0.0.1'

Use underscore characters to make large numeric literals easier to read and understand. For example, change:

65536

to:

65_536

Documentation

The PEP-8 style guide recommends adding docstrings for functions. For example:

def portscan(port):
 """ Scan a port """

The docstring should also describe what the input is and what the function does.

Simpler

Since the x variable is not used inside this for loop:

for x in range(100):

the _ placeholder can be used:

for _ in range(100):

f-string

The following line:

print('Time taken:', time.time() - startTime)

can be improved using an f-string with a precision specifier to limit the number of places after the decimal:

print(f'Time taken: {time.time() - startTime:.2f} seconds')

The message is also clearer with the addition of time units ("seconds").