pinging network script

jschiwal · 11-26-2007, 09:16 AM

He said he has 50 devices to check. 50 units * several minutes is a very long time.

Something like this in bash using your same test would work:

Code:

read foo < /dev/tcp/hpmedia/22 &
[1] 533
jschiwal@hpamd64:~> sleep 5; kill $! && ssh=closed || ssh=open
[1]+  Done                    read foo < /dev/tcp/hpmedia/22
bash: kill: (533) - No such process
jschiwal@hpamd64:~> read foo < /dev/tcp/hpmedia/23 &
[1] 541
jschiwal@hpamd64:~> sleep 5; kill $! && telnet=closed || telnet=open
jschiwal@hpamd64:~> echo $telnet
closed
[1]+  Terminated              read foo < /dev/tcp/hpmedia/23
jschiwal@hpamd64:~> echo $ssh
open

I haven't used the ksh shell, but it probably has a similar job control feature. "$!" is the last background process. I'm using a double negative. If the port is open, killing the last background process fails.

jlliagre · 11-26-2007, 10:51 AM

Are you observing a stall even while no firewall is blocking the inactive service port ?

metallica1973 · 11-26-2007, 11:18 AM

I tested the scipt and it is rather slow internally. It seems as though it is taking a couple of seconds to determine whether or not the device is up or not(timing out). It there anyway to shorten the length of time it takes to access the device and determine whether or not telnet port 23 is open. thanks

acid_kewpie · 11-26-2007, 11:58 AM

why has no one commented on my awesome perl solution?

metallica1973 · 11-26-2007, 03:26 PM

I am willing to try your one liner perl script but will it produce the output that I am looking for?

PHP Code:



$ cat check.ksh 
#!/bin/ksh 
exec 2>/dev/null 
printf " %-20.20s %-8s %-6s\n" host status telnet 
for host in $(<list) 
do 
        status=down 
        telnet=closed 
        if ping $host 5 >/dev/null 2>&1 
        then 
                status=up 
                read foo < /dev/tcp/$host/23 && telnet=open 
        else 
                telnet="n/a" 
        fi 
        printf " %-20.20s %-8s %-6s\n" $host $status $telnet 
done 
$ ./check.ksh 
 host                 status   telnet 
 127.0.0.1            up       closed 
 192.168.1.1          up       open   
 192.168.1.2          up       closed 
 192.168.1.3          down     n/a

This is awesome but slow! thanks

jlliagre · 11-26-2007, 06:40 PM

You can reduce the ping timeout from 5 seconds to 2 or even 1 second and so improve my script scan performance.

The timeout is the second parameter of the ping command:

Code:

if ping $host 5 >/dev/null 2>&1

There may be a risk of false negative if your WAN is too busy though.

metallica1973 · 11-26-2007, 07:31 PM

awesome. All of you rock.

jschiwal · 11-28-2007, 01:49 AM

Quote:

Originally Posted by acid_kewpie

why has no one commented on my awesome perl solution?

I did try it and it seems to hang as well. I used it to test port 23 on "hpmedia.jesnet".

It worked OK testing port 22 however.

Alien_Hominid · 11-28-2007, 07:56 AM

Telnet connection timeout is too high. You can use telnet command on any host and you'll see that if the host is up, telnet will need at least a minute to respond that the service in unavailable.

telnet google.com is now running maybe for 4 minutes and still hasn't finished

acid_kewpie · 11-28-2007, 10:07 AM

sure, i *think* the use of the telnet client in itself has been disowned now though.

Alien_Hominid · 11-28-2007, 10:52 AM

What I wanted to say is if telnet client checks for so long if port is open, probably all scripts will do smth similar.

acid_kewpie · 11-28-2007, 11:33 AM

no, becuase telnet as a client will retry, generally do an exponentially timed backoff between attempts and such. nmap will send one SYN packet, expect one SYNACK back within a few milliseconds

metallica1973 · 11-28-2007, 11:57 AM

I promise I wont ask for anymore help but how can I have this script:

PHP Code:



$ cat check.ksh  
#!/bin/ksh  
exec 2>/dev/null  
printf " %-20.20s %-8s %-6s\n" host status telnet  
for host in $(<list)  
do  
        status=down  
        telnet=closed  
        if ping $host 5 >/dev/null 2>&1  
        then  
                status=up  
                read foo < /dev/tcp/$host/23 && telnet=open  
        else  
                telnet="n/a"  
        fi  
        printf " %-20.20s %-8s %-6s\n" $host $status $telnet  
done  
$ ./check.ksh  
 host                 status   telnet  
 127.0.0.1            up       closed  
 192.168.1.1          up       open    
 192.168.1.2          up       closed  
 192.168.1.3          down     n/a

to include the hostname of the device and have two different categories of devices like NAM's and Sniffers. like for example:

PHP Code:



 NAM             status   telnet  
 127.0.0.1       up       closed  
 192.168.1.1     up       open    
 192.168.1.2     up       closed  
 192.168.1.3     down     n/a   
 
 Sniffers       status    telnet  
 127.0.0.1       up       closed  
 192.168.1.1     up       open    
 192.168.1.2     up       closed  
 192.168.1.3     down     n/a

help

Alien_Hominid · 11-28-2007, 11:59 AM

Op mentioned he can't use nmap and I don't know how perl or /dev/tcp/$host/23 peform their checks. Sorry for misinformation then. Based my opinion on that that all need several minutes to respond.

acid_kewpie · 11-28-2007, 12:57 PM

no, certainly in perl it only does one attempt, i assume the onus is on the coder to implement a retry mechanism.