lang/python/ PingExample1

This pings every 192.168.1.x address, compiles a list of those who replied (within 1 second which is fine for a LAN). It then looks in /etc/hosts to see which are recognised and lists out which ip addresses (actually just the x) have known names and which do not. I wrote this because the expensive Netgear Orbi doesn't allow you to call a local machine by an unqualified name (e.g. ping pi3 doesn't work unless pi3 is in the /etc/hosts file).

The code:

#!/usr/bin/env python3
from threading import Thread
from subprocess import run, PIPE, DEVNULL

def ping(host):
  m = run(["ping","-c1","-W1",host],stdout=DEVNULL,stderr=DEVNULL)
  return m.returncode
def p(n):
  host = f"192.168.1.{n}"
  return ping(host) == 0
s = set()
def task(n):
  if p(n):
    s.add(n)
ts = []
def main():
  for i in range(2,255):
    t = Thread(target=task,args=(i,))
    ts.append(t)
    t.start()
  for t in ts:
    t.join()
  print(" ".join(map(str,sorted(s))))
  hosts = open("/etc/hosts").read().rstrip().splitlines()
  hosts = list(filter(lambda t: t.startswith("192"),hosts))
  hs = list(map(lambda t: int(t.split(" ")[0].split(".")[3]),hosts))
  hm = { hs[i]:hosts[i] for i in range(len(hs)) }
  for n in sorted(s):
    if n in hm:
      print(f"{n} : {hm[n]}")
    else:
      print(f"{n} unknown")

if __name__ == "__main__":
  main()