So yesterday I was practicing what I learnt over the past few days and decided to create a script to scan through all the IPs in the local network and check which ones are being used.
I used subprocess the use the "ping" command with a given timeout, and other few libraries such as docopt, threading and time for common tasks such as handling command line arguments, threading, waiting code etc...
Here's the script:
""" ipcheck.py - Getting available IPs in a network.
Usage:
ipcheck.py -h | --help
ipcheck.py PREFIX
ipcheck.py [(-n <pack_num> PREFIX) | (-t <timeout> PREFIX)]
Options:
-h --help Show the program's usage.
-n --packnum Number of packets to be sent.
-t --timeout Timeout in miliseconds for the request.
"""
import sys, os, time, threading
from threading import Thread
from threading import Event
import subprocess
import docopt
ips = [] # Global ping variable
def ping(ip, e, n=1, time_out=1000):
global ips
# FIX SO PLATFORM INDEPENDENT
# Use subprocess to ping an IP
try:
dump_file = open('dump.txt', 'w')
subprocess.check_call("ping -q -w%d -c%s %s" % (int(time_out), int(n), ip),
shell=True, stdout=dump_file, stderr=dump_file)
except subprocess.CalledProcessError as err:
# Ip did not receive packets
print("The IP [%s] is NOT AVAILABLE" % ip)
return
else:
# Ip received packets, so available
print("The IP [%s] is AVAILABLE" % ip)
#ips.append(ip)
finally:
# File has to be closed anyway
dump_file.close()
# Also set the event as ping finishes
e.set()
ips.append(1)
def usage():
print("Helped init")
def main(e):
# variables needed
timeout = 1000
N_THREADS = 10
# Get arguments for parsing
arguments = docopt.docopt(__doc__)
# Parse the arguments
if arguments['--help'] or len(sys.argv[1:]) < 1:
usage()
sys.exit(0)
elif arguments['--packnum']:
n_packets = arguments['--packnum']
elif arguments['--timeout']:
timeout = arguments['--timeout']
prefix = arguments['PREFIX']
# Just an inner function to reuse in the main
# loop.
def create_thread(threads, ip, e):
# Just code to crete a ping thread
threads.append(Thread(target=ping, args=(ip, e)))
threads[-1].setDaemon(True)
threads[-1].start()
return
# Do the threading stuff
threads = []
# Loop to check all the IP's
for i in range(1, 256):
if len(threads) < N_THREADS:
# Creating and starting thread
create_thread(threads, prefix+str(i), e)
else:
# Wait until a thread finishes
e.wait()
# Get rid of finished threads
to_del = []
for th in threads:
if not th.is_alive(): to_del.append(th)
for th in to_del: threads.remove(th)
# Cheeky clear init + create thread
create_thread(threads, prefix+str(i), e)
e.clear()
time.sleep(2*timeout/1000) # Last chance to wait for unfinished pings
print("Program ended. Number of threads active: %d." % threading.active_count())
if __name__ == "__main__":
ev = Event()
main(ev)
The problem I'm having is that, although I'm setting a timeout (in milliseconds) for the ping command, some threads do not finish some reason. I fixed this temporarily by making all the threads daemonic and waiting twice the timeout after the program finishes (last few lines in main), but this doesn't work as expected, some threads are still not finished after the sleep.
Is this something to do with the command ping itself or is there a problem in my design ?
Peace!
