IsPortOpenOnRemoteHost

Essentially we want to replicate

nmap -p 4000-4100 hostname

Source: this gist

For this particular use of nmap, I have this Python script, which outputs JSON (so avoids the need to parse the output of nmap). It runs each attempt to connect in a separate thread, each with a 1 second timeout, which is fine for a LAN.

#!/usr/bin/env python3
import json
import sys
import socket
from threading import Thread

def isOpen(ip,port):
  s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
  try:
    s.settimeout(1.0)
    s.connect((ip, int(port)))
    s.shutdown(socket.SHUT_RDWR)
    s.close()
    return True
  except Exception as e:
    return False

class Pinger:
  def __init__(self,host,baseport=7000,count=100):
    self.host = host
    self.baseport = baseport
    self.count = count
    self.targets = set(range(count))
    self.openports = set()
    self.threads = []
    self.ports = set()
    for n in self.targets:
      thread = Thread(target=self.task,args=(n,))
      self.threads.append(thread)

  def task(self,n):
    targets = self.targets
    ports = self.ports

    if n in targets:
      targets.remove(n)
      port = n + self.baseport
      if isOpen(self.host,port):
        ports.add(n)

  def start(self):
    for thread in self.threads:
      thread.start()

  def join(self):
    for thread in self.threads:
      thread.join()

  def result(self):
    return (self.host,list(sorted(self.ports)))

hosts = sys.argv[1:]
pingers = []
for host in hosts:
  pingers.append((host,Pinger(host)))
for host, pinger in pingers:
  pinger.start()
for host, pinger in pingers:
  pinger.join()
data = {}
for host, pinger in pingers:
  _, ports = pinger.result()
  data[host] = ports

j = json.dumps(data)
print(j)