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How to find if port taken in UNIX (Solaris 9)

Posted on 2007-11-28
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Last Modified: 2013-12-27
Hello

2 questions (UNIX Solaris 9:

How do I find available ports on a unix system.

Also if I want to see if a port is listening, to see if the service using that port has started, what is the way to do this.

Thank you:)
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Question by:atwork2003
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omarfarid earned 250 total points
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Hi,

To see if a port is currently is in use and a process is listening to it, run

netstat -an | grep LISTEN

if you look at /etc/services , you will see the well know services ports (e.g. ftp, telnet, etc).

Any port that is not in use is a free one.

To verify also, you may use telnet to test tcp ports

e.g.

telnet ipaddress tcpport

telnet 10.0.0.1 25

if you get connected then the port is in use, if you get the message connection refused then it is not running.

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by:atwork2003
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Thank you this is really great.

also if I am logged into the server, can I do a grep for a specific port
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by:omarfarid
omarfarid earned 250 total points
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Hi,

The netstat -an | grep LISTEN will give you this

or if it is tcp port you can try telnet but to the server ip or 0

e.g.

telnet 0 25

will connect you to port 25 on the local m/c you are logged to (unless the service is listening to a particular ip on the m/c)

or

e.g.

telnet serveripaddress 25
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by:robocat
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> also if I am logged into the server, can I do a grep for a specific port

Yes, suppose you want to check if port 256 is currently in use:

netstat -an | grep "*.256"

      *.256                *.*                0      0 49152      0 LISTEN

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by:bpeterse
bpeterse earned 125 total points
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If your intent is to create your own service on an open port - or to change ports for an existing service, you can refer to a list of assigned ports:services at the following links:
http://www.iana.org/assignments/port-numbers
http://www.iss.net/security_center/advice/Exploits/Ports/
http://www.chebucto.ns.ca/~rakerman/port-table.html

Any one that is not already assigned per IANA, then you can use it for your own purposes.  See the ff. links for adding new services/processes.

http://docs.sun.com/app/docs/doc/816-1048/6m7gaddjl?a=view#manageprogramprivileges-16
http://docs.sun.com/app/docs/doc/816-1048/6m7gaddjl?a=view#manageprogramprivileges-31
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by:omarfarid
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Hi,

bpeterse:

Thank you for the links.

Do you think that the IANA ports are included in /etc/services file?

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by:bpeterse
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I'm sure some are - but since I didn't understand his intent (as I indicated in the response), I thought I'd include that reference just to be thorough.  Just trying to help...
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by:omarfarid
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Hi,

don't misunderstand me, I was trying to see if /etc/services has the up to date information of the well known ports.

Thank you again.
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Author Closing Comment

by:atwork2003
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I apologize for delay in closing. But exceptional help, can not thank you enough. Dont know what I would have done without my account on EE
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by:omarfarid
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Welcome at any time.
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