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Anyways to find out that Red Hat Linux Server is accepting incoming trafic on a specific port?

Posted on 2006-06-23
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Last Modified: 2013-12-06
Hi,

Does anyone know how to check is a specific port (like 3300) is accepthing incoming traffic on the Redhat Linux server? Thanks.
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Question by:huabin
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Accepted Solution

by:
Gyanendra_Chandra earned 100 total points
ID: 16972830

Go to console on the same server

telnet server_ip 3300

this should show u a blank screen or a message.

This is a local test that the service is accepting the connection on the server.

But if firewall is running on the server u need to check the port from a different computer in the same ip subnet.

or u can use ethereal or dsniff for capturing packets coming on specific port.


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LVL 22

Assisted Solution

by:pjedmond
pjedmond earned 200 total points
ID: 16972999
Type:

netstat -a | grep listen

And you'll get a list of all the ports that have a process listening on, rather than having to try 'telnetting' to every port!

Of course firewall rules could restrict connections from certain ip addresses, in which case the 'telnet test' (mentioned already) is an excellent test.

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LVL 20

Assisted Solution

by:nedvis
nedvis earned 100 total points
ID: 16973140
Port 330 is used by BMC Software Patrol Agent

PORT 3300 - Information
Port Number:      3300
TCP / UDP:      TCP
Delivery:      Yes
Protocol / Name:      bmcpatrolagent
Port Description:      BMC Patrol Agent
Virus / Trojan:      No

-------------------------------------
pjedmont you were very  close, acctually command huabin will need here is:

netstat -a | grep 3300

if the port is active it will return message:  CONNECTED


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LVL 22

Assisted Solution

by:pjedmond
pjedmond earned 200 total points
ID: 16973169
:) Well spotted the deliverate mistake. I meant it to be:

netstat -a | grep -i listen

It does state (like 3300), which can be interpreted as wanting either a specific or general solution. Giving a list of listening ports answers the question in a slightly obtuse manner. The reason for the approach I gave was that the approach

netstat -a | grep 3300

probably works for port 3300, but *does not* work for all ports is because for example port 22 gets replaced by ssh and port 80 by httpd. The approach I gave gives a sensible sized list for browsing.

As always, there are many ways to skin a cat;)

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LVL 2

Assisted Solution

by:linux2000in
linux2000in earned 50 total points
ID: 16975519
Hi huabin,

Well yes u can see using state of TCP/IP connection at 3300 port , but again if u want to go in more deatils .
you can use tcpdump to sniff traffice u will get TCP/IP in-depth details..so u can get conformation server accept connection and processing them or not ?


regards
niri

www.linux-gujarat.co.in : GLUG: Learn Linux different WAY !!
www.linux-directory.net  : It's all about Open Source & Linux.
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LVL 51

Assisted Solution

by:ahoffmann
ahoffmann earned 50 total points
ID: 16976380
> ..  how to check is a specific port (like 3300) is accepthing incoming traffic
how should tcpdump answer this question?
It cannot. Dot Period.
netstat,  as shown before, is one solution.
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