check connectivity of a port 1

[ac325ci]

im trying to write a script to check connectivity to a port.. what is the best way to achieve this ? if port is listening on target server then return code 0..thanks

 

[Annihilannic]

Something like:

[tt]if telnet hostname portnumber < /dev/null 2>&1 | grep refused
then
return 1
else
return 0
fi[/tt]

Annihilannic.

 

[ac325ci]

ty i will test it..

 

[ac325ci]

Annihilannic, is there a way to allow this attempt for like 5 secs or so ? prob is when the machine is down , the script sits there waiting telnet hostname 22|grep refuse to finish.. takes a long time.. ie

+ telnet hostname 22
+ 0< /dev/null 2>& 1
+ grep refused

 

[KenCunningham]

Maybe a simple ping would be faster? Maybe not...

I don't mind people who aren't what they seem. I just wish they'd make their mind up.

 

[Annihilannic]

ping won't test whether a specific port is open, but it's a good idea nonetheless... i.e. first ping the host to see if it is up at all, and then attempt the telnet. You can usually set a short timeout on the ping to speed it up as well. If the host is up but the port is closed, then the telnet should fail to connect immediately.

Annihilannic.

 

[ac325ci]

yes, im pinging the host first before attemptin but the prob is that some servers are behind firewalls and icmp requests are turned off

 

[Annihilannic]

You could try something like this with a background timer to kill the telnet after a short while:

#!/bin/ksh

# Hide the messages about terminated processes.
exec 2> /dev/null

function testport()
{
        (
                if sleep 10
                then
                        ps -o pid,comm | awk 'NR > 1 && /telnet/ {print $1}' | xargs -r kill
                fi
        ) &

        if telnet $1 $2 < /dev/null 2>&1 | grep -1 '^Connected'
        then
                RETURN=0
        else
                RETURN=1
        fi

        ps -o pid,comm | awk 'NR > 1 && /sleep/ {print $1}' | xargs -r kill

        return $RETURN
}

testport localhost 26 && echo localhost 26 is open || echo localhost 26 is closed
testport nothing 26 && echo nothing 26 is open || echo nothing 26 is closed
testport localhost 25 && echo localhost 25 is open || echo localhost 25 is closed
testport example.com 25 && echo example.com 25 is open || echo example.com 25 is closed

Annihilannic.

 

[ac325ci]

thanks a lot will do..!!