How to Create a shell script to test the telnet connection status

yhcheong · #1 (**permalink**) 03-19-2009

Hi friends,

I'm newbie to shell script. I wanted to create a shell script which able to write a result for all the telnet connection status. For example, from this machine I want to test the telnet connection (total 100+ servers) with this machine.

Any idea how to write this shell script?
Appreciate if you guys could help on this.
Thanks !

ghostdog74 · #2 (**permalink**) 03-19-2009

if you have Python, you can use the script here. the Python script tests for ports. For telnet, just substitute with 23. other solutions include using nmap.

yhcheong · #3 (**permalink**) 03-19-2009

Thanks for the feedback.
The current machine is running on sun solaris OS, it does not has python. The script I want to test is test the telnet connection with other 100+ machines. Is there any shell script?
The nmap seems like I need to install on the server.
Thanks in advance

pludi · #4 (**permalink**) 03-19-2009

nmap isn't quite that useful to test connections. You could install netcat and test the connection using the -z switch, eg

Code:

netcat -z ${MACHINE} 23
if [ $? -eq 0 ]
then
    echo "Telnet accepting connections"
else
    echo "Telnet connections not possible"
fi

Or, if you have bash available and don't want to install anything else you could try replacing the netcat call with

Code:

exec 3>/dev/tcp/${MACHINE}/23

But this is really, really fugly.

yhcheong · #5 (**permalink**) 03-19-2009

Hi Pludi,

Thanks for the suggestion, if running bash. I think it is same by executing below command
for one by one(since I have hundred over telnet connection). The telnet connection port is
2071

% telnet 10.x.x.x 2071

for the bash command
exec 3>/dev/tcp/${10.x.x.x}/2071
if [ $? -eq 0 ]
then
echo "Telnet accepting connections"
else
echo "Telnet connections not possible"
fi

It seems like not working.

bash: /dev/tcp/${10.x.x.x}/2071: bad substitution.

Do you have any idea which can lead me to run the script in one shot, and the output is the hundred over telnet connection status. THanks in advance!

ghostdog74 · #6 (**permalink**) 03-19-2009

what version is your sun solaris OS?

pludi · #7 (**permalink**) 03-19-2009

Please use [code ][/code] (sans the space) tags for source and listings, it's easier to read.

Quote:

Originally Posted by yhcheong

Code:

exec 3>/dev/tcp/${10.x.x.x}/2071
if [ $? -eq 0 ]
then
    echo "Telnet accepting connections"
else
    echo "Telnet connections not possible"
fi

bash: /dev/tcp/${10.x.x.x}/2071: bad substitution.

The ${MACHINE} that I used was in preparation for the loop that you'll need for that many machines (it's substituted by the value of the variable MACHINE)

Change it like this and try again

Code:

MACHINE=10.0.0.1 # Change to what ever you need
exec 3>/dev/tcp/${MACHINE}/2071
if [ $? -eq 0 ]
then
    echo "Telnet accepting connections"
else
    echo "Telnet connections not possible"
fi

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