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Linux Port Checking

Posted on 2006-06-20
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Last Modified: 2010-05-18
Hi,

On Red Hat Linux, how do I know is a port is using by programs?

I simply want to check is port 3300 open or avaiable to use.

thanks,

Jack

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Question by:huabin
4 Comments
 
LVL 10

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by:
Luxana earned 200 total points
ID: 16948635
Hi,

One such a tool is nmap

Example:

#nmap localhost

Starting nmap 3.81 ( http://www.insecure.org/nmap/ ) at 2006-06-21 15:19 EST
Interesting ports on localhost.localdomain (127.0.0.1):
(The 1653 ports scanned but not shown below are in state: closed)
PORT     STATE SERVICE
22/tcp   open  ssh
25/tcp   open  smtp
111/tcp  open  rpcbind
113/tcp  open  auth
443/tcp  open  https
614/tcp  open  unknown
631/tcp  open  ipp
1016/tcp open  unknown
3306/tcp open  mysql
5432/tcp open  postgres

Nmap finished: 1 IP address (1 host up) scanned in 0.474 seconds
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LVL 16

Assisted Solution

by:Blaz
Blaz earned 100 total points
ID: 16948662
netstat -ln | grep :3300
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LVL 2

Assisted Solution

by:fpintos
fpintos earned 100 total points
ID: 16949340
You can also use

lsof -i :3300

to list all processes that are using port 3300
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LVL 3

Assisted Solution

by:Ustas
Ustas earned 100 total points
ID: 16950149
Try

netstat -napt

for all tcp ports and processes using them (in your case: netstat -napt | grep -w 3300)

or

netstat -napu

for all udp ports and their respective processes.
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