Open Port?

[Nobody's Hero]

My dba asked me how I can ping a port, or to see if the port is open.

How can I do this with ping. If I cant,
how do I do it with lsof.

[mirco_1]

hi,

# telnet <#port>

DM.

[Ralph Grothe · Accepted solution]

lsof -i :

or

netstat -an | awk '$4~/\.$/'

or

nmap -P0 -p

or the suggested telnet client
or a custom client for the protocol

[Biswajit Tripathy]

I would recommend nmap (as suggested by
Ralph). Very simple to use and very effective
(see nmap.org).

One problem with "netstat -an" is, the port
will be marked as "listen" even if it is
blocked by a firewall at lower layer.

I use the attached simple script for
portscanning (this script should run from a
remote machine). Run without any argument to
see the usage info.

- Biswajit

[Raj D.]

Hi Robert ,

Download the lsof utility from http://hpux.cs.utah.edu/ , and check # lsof -i :

Also can be checked with # netstat -n | grep EST


hth,
Raj.

[Muthukumar_5]

To see whether a port is open or not as,

# netstat -na | grep

Another way is with telnet as,

# telnet

You have to get connected message then port is opened. Else it is not. To come back to shell then ctrl + ] will ask telnet>quit put there in that prompt.

Best utility to use is with lsof tool.

hth.

[Arunvijai_4]

Latest version of "lsof" is here,
http://hpux.connect.org.uk/hppd/hpux/Sysadmin/lsof-4.76/

Man page is at,
http://hpux.connect.org.uk/hppd/hpux/Sysadmin/lsof-4.76/man.html

-Arun

[Thomas Bianco]

my personal fav is nmap, from insecure.org

bear in mind this is a security tool, and it's considered... impolite... to run it against a server without the owners permission.