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Port checking using the ksh shell

Posted on 2004-08-17
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Last Modified: 2013-12-27
I am after checking ports using telnet in the ksh shell, i need to telnet into the relevant ip and port check if there is connectivity if not display an error.



Thanks for Your Help,
Mike
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Question by:Slightly_Imperfect
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LVL 18

Accepted Solution

by:
liddler earned 63 total points
ID: 11821081
Which ports are you checking? all? Just a few?

You are going to have to issue the telnet, and pipe stderr somewhere, like
telnet $ip $port 2>$out

You may want this in a loop for your ports, if there are many and in a second loop if there are lots of ips

for ip in 10.10.0.1 10.0.0.2 10.0.0.2
do
for port in 20 21 22 25 80 110 443
cat /dev/null >/tmp/out
do
telnet $ip $port 2> /tmp/out
fail=`grep Unable /tmp/out`  #bit messey using a tmp file
if [[ -n $fail ]];then
echo "failed"
done
done

However, telnet may hang if it actually connects, so you might want to use kill / pkill to kill off any telnet spwned by this script running after a short time (say 1 second?)

 
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Author Comment

by:Slightly_Imperfect
ID: 11821109
how would you add the kill part to the actual script ?



Thanks,
Mike
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LVL 18

Expert Comment

by:liddler
ID: 11821295
something like
telnet $ip $port 2> /tmp/out &
sleep 1
pkill telnet

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LVL 48

Assisted Solution

by:Tintin
Tintin earned 62 total points
ID: 11826321
telnet isn't the best tool for this type of job.  You'd be better off with something like netcat or similar.
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