[Python]Listing live nodes on LAN..how to make it fast?

**Dhiraj Thakur(Invincible)** · September 26th, 2012

Code:

import socket 
from socket import gaierror,herror 
ip='192.168.0.' 
name={ ##name resolver 'Dhir':'Dhiraj PC'## } 
for i in range(100,110): 
    add=ip+str(i) 
    try: 
        up=socket.gethostbyaddr(add)[0] 
        if(name.has_key(up)): 
            print add+'--{'+name.get(up)+'} is up!' 
        else :  
            print up+' is up!' 
    except herror: 
        pass

This is my code...is there any way to make it fast....i can tolerate 3 sec delay but not more than 5 second when checking for every node..

**Tony Flury** · September 26th, 2012

How many nodes on your network ?

I think 5 seconds to check on 10 potential nodes - i.e. 1/2 second for each node is not bad considering.

I note that with your code it is actually only looking for one node (as defined in the name dictionary), so why not loop around the name dictionary and do a gethostbyname, rather than go through 10 IP addresses looking for one name ?

also strictly speaking you should be using

Code:

if up in name:

rather than

if name.has_key(up): ## has_key is deprecated in Python 2.7 

and 

since you already know that the key exists, you can use : 

name[up]

rather than

name.get(up)

Also from what i understand (i might be wrong) that gethostbyname and gethostbyaddr don't actually tell you if the node is live - it simply resolves the dns lookup - or does a reverse DNS lookup, and the DNS entry can exists by the actual node could be dead - unless your network does some dynamic DNS deal.

To check if the node is alive you may well need to execute a ping or similar.

**juancarlospaco** · September 27th, 2012

Talk to the Broadcast, not by range()

ie: ping to broadcast

**Dhiraj Thakur(Invincible)** · September 27th, 2012

Originally Posted by juancarlospaco

Talk to the Broadcast, not by range()

ie: ping to broadcast

You mean like this?

Code:

os.system("ping -b -c 3 192.168.0.255")

Originally Posted by Tony Flury

How many nodes on your network ?

I think 5 seconds to check on 10 potential nodes - i.e. 1/2 second for each node is not bad considering.

I note that with your code it is actually only looking for one node (as defined in the name dictionary), so why not loop around the name dictionary and do a gethostbyname, rather than go through 10 IP addresses looking for one name ?

also strictly speaking you should be using

Code:

if up in name:

rather than

if name.has_key(up): ## has_key is deprecated in Python 2.7 

and 

since you already know that the key exists, you can use : 

name[up]

rather than

name.get(up)

Also from what i understand (i might be wrong) that gethostbyname and gethostbyaddr don't actually tell you if the node is live - it simply resolves the dns lookup - or does a reverse DNS lookup, and the DNS entry can exists by the actual node could be dead - unless your network does some dynamic DNS deal.

To check if the node is alive you may well need to execute a ping or similar.

I have to check for live nodes not particular nodes..and i have about 4-5 computers connected via a switch..
and my code is taking upto 5-6 seconds for every ip lookup..this is what's bugging me..
and about gethostbyname/addr...what else can i do to find names of comp. on my network?

**ofnuts** · September 27th, 2012

Originally Posted by Dhiraj Thakur(Invincible)

You mean like this?

Code:

os.system("ping -b -c 3 192.168.0.255")

I have to check for live nodes not particular nodes..and i have about 4-5 computers connected via a switch..
and my code is taking upto 5-6 seconds for every ip lookup..this is what's bugging me..
and about gethostbyname/addr...what else can i do to find names of comp. on my network?

Not expert enough in that side of Python, but I would definitely try to use one thread per host checked and start several threads in parallel.