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How to find out Active Connections or which Ports are open/listening on Linux

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http://linuxers.org – While managing a server or your home desktop, sometimes you might want to check out which ports are currently being used by which applications, what all TCP/UDP connections are active at the moment or other similar cases. There are two basic command line tools present in almost all the Linux/UNIX based systems - netstat and lsof, that might help you out with such queries. Before starting it would be good to know about these two commands. Netstat is used to display network connections, routing tables and a whole bunch of network and interface st (General)

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Submitted by linuxfan on 05/18/2010

Stories similar to How to find out Active Connections or which Ports are open/listening on Linux

A few days ago, I wrote about monitoring your system's network activity on linux, a command line approach.

This question is similar to Network port open, but no process attached?

I've tried everything from there, reviewed the logs, etc... and can't find anything.

My netstat shows a TCP listening port and a UDP port without a pid.

Hi Guys,

Question...

How on earth do I view listening ports and est ports? Netstat on ubuntu is giving completely different output than any other distro i have used?

( Cont copy and past because its via a hyperv console..

I'm currently using a Windows box, running Chrome 27 on the dev channel, and I have what I believe to be an unusually large number of listening connections connected with the process.

The following command returns 268 listening ports: netstat -aon|find /i /c "11692" (where in this case 11692 is the main chrome process)

This is what some of the ports looks like from netstat: UDP 0.0.0.0:6248

NetStat unlike Wireshark is a command line tool used to show the network status. It is used to monitor incoming and outgoing network connections. It is also used for monitoring various network interface statistics. So lets see how to use NetStat to monitor the network connections. Click here to read more | Tweet this

Hi all,

I am programming on Linux middleware so I need to get a list of all active TCP connections. Is there any API to get such information? I know I can find the connections in /proc/net/tcp, but how to find the PIDs corresponding to the connections? Apparently ps or netstat command is not an option since it is a middleware. Any help will be appreciated!

Cheers Tete

I have been obtaining errors like below because I did not specify enough ports for the active FTP connections.

Response: 150 Opening data channel for directory list. Response: 425 Can't open data connection.Error: Failed to retrieve directory listing

Things seem to work nicely with limited ports, but when I perform actions that cause very rapid short-lived connections, something like 20-30% o

Netactview (Net Activity Viewer) is a graphical network connections viewer for Linux, similar in functionality with Netstat. It includes features like process information, host name retrieval, automatic refresh and sorting.

I know how to do the opposite (find out what process has a given port open) using lsof or netstat, but extensive research on Google hasn't helped me solve the reverse problem.

I know I could use "netstat -np" combined with some grep and sed, but it seems hacky. Is there a reversed version of "lsof -i tcp:80" that will show me all the local ports opened by a given process?