Python Hostname resolving very slow

Question

I am currently trying to build a little Networkscan for my home network. To resolve the hostnames, I want to use this function called within a for loop iterating over a range of IPs. That is doing very well, but I think the gethostbyaddr(tgtHost) function is very very slow. Is there a way to speed things up or use alternative functions ?

def fn_hostscan(tgtHost):

    response = os.system("ping -n 1 " + tgtHost + "> C:\\temp\log.txt")

    if response == 0:
        try:
            tgtName = gethostbyaddr(tgtHost)
            print("\n[+] " + tgtHost + " = " + tgtName[0])
        except:
            dummy = 0
    else:

    print("\n[-]" + tgtHost + " = None found")

Is there any way I can encourage this question to be closed? — Kelvin, Feb 11 '16 at 21:46

score 1 · Answer 1 · edited May 23 '17 at 11:45

1

Taking a look at whats around for this:

Would this suit your purposes? - Finding local IP addresses using Python's stdlib

import socket 
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.connect(("gmail.com",80))
print(s.getsockname()[0])
s.close()

edited May 23 '17 at 11:45

Community

1
1

answered Feb 26 '15 at 14:17

Kelvin

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score 1 · Answer 2 · answered Mar 02 '15 at 08:23

gethostbyaddr and similar functions are dependant of your resolv.conf (see http://linux.die.net/man/5/resolv.conf).

your DNS resolver is slow (try using Google's Public DNS)
some IPs do not have PTR records or their NS are offline, the default timeout is 5sec - keep that in mind while "looping"

To improve performance you might want to parallelize it, use a fast resolver and keep the timeout setting to a minimum.

If you can, use libs similar to http://c-ares.haxx.se/

Python Hostname resolving very slow

2 Answers2