This is a text-only version of the following page on https://raymii.org:
---
Title : Get number of incoming connections on specific port with ss
Author : Remy van Elst
Date : 25-08-2020
Last update : 07-11-2020
URL : https://raymii.org/s/snippets/Get_number_of_incoming_connections_on_specific_ports_with_ss.html
Format : Markdown/HTML
---
Recently I had to write a few monitoring plugins, one of which was a count of
incoming established connections to a specific network port. In the past I
would have used `netstat` and a combination of `grep` and `wc` to filter out only
specific ports and established connections, but nowdays `netstat` is replaced by
`ss` on ubuntu. `ss` has options to filter directly on all sorts of stuff, like
state, ports, protocol, making the command I use more readable and use less
pipes.
Here's an example of the graph my code makes:
![munin ports][2]
[If you like this snippet, consider sponsoring me by trying out a Digital Ocean
VPS. With this link you'll get $100 credit for 60 days). (referral link)][99]
The below snippet is from one of my webservers. You can check the [manpage][1]
for more information, they have another quite elaborate example:
ss -o state fin-wait-1 '( sport = :http or sport = :https )' dst 193.233.7/24
List all the tcp sockets in state FIN-WAIT-1 for our apache to network 193.233.7/24
and look at their timers.
### connection filtering with ss
This is the command, it even works for non-root users, which was nice since my monitoring
plugins do not run as root.
ss --all --numeric --no-header state established '( sport = :443 )'
Output:
tcp 0 0 128.199.39.10:443 178.200.216.97:55467
tcp 0 0 128.199.39.10:443 137.8.9.12:39760
tcp 0 0 128.199.39.10:443 213.64.253.119:57065
To count, just add `wc -l`:
ss --all --numeric --no-header state established '( sport = :443 )'| wc -l
Output:
4
Change the port or add more filters, `'( sport = :443 or sport = :80 )'` (mind
the trailing space after the port number), you should be able to figure it out.
## netstat version
On a system that still has `netstat`, I use the following command:
netstat -anp | grep :443 | grep ESTABLISHED | wc -l
## Long running connections
Update: 2020-11-08
If you want to measure long running connections, a somewhat working example is
the following:
comm -1 -2 <(ss --all --numeric --no-header state established '( sport = :443 )' | awk '{print $5}' | awk -F: 'NF{--NF};1' | sort -u) <(sleep 5; ss --all --numeric --no-header state established '( sport = :443 )' | awk '{print $5}' | awk -F: 'NF{--NF};1' | sort -u) | wc -l
The `comm` command is a reverse `diff` (show all things in common), `-1` and
`-2`. The command executed is the same, only the last command has a `sleep 5`
in front of it:
ss --all --numeric --no-header state established '( sport = :443 )' | awk '{print $5}' | awk -F: 'NF{--NF};1' | sort -u
It prints all established connections to port 443, strips out the part after
the last colon (the two awk commands) so that it works with IPv6 as well and
then sort the list, removing duplicates. NATted connections will be counted
once.
This way, you get all IP addresses that have an established connection for at
least 5 seconds in your graph.
I'm using this as a brute force way to measure video live stream viewers.
Regular web requests almost never get into `established`, but these long
running connections do.
[1]: http://manpages.ubuntu.com/manpages/xenial/man8/ss.8.html
[2]: /s/inc/img/munin_port.png
---
License:
All the text on this website is free as in freedom unless stated otherwise.
This means you can use it in any way you want, you can copy it, change it
the way you like and republish it, as long as you release the (modified)
content under the same license to give others the same freedoms you've got
and place my name and a link to this site with the article as source.
This site uses Google Analytics for statistics and Google Adwords for
advertisements. You are tracked and Google knows everything about you.
Use an adblocker like ublock-origin if you don't want it.
All the code on this website is licensed under the GNU GPL v3 license
unless already licensed under a license which does not allows this form
of licensing or if another license is stated on that page / in that software:
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
Just to be clear, the information on this website is for meant for educational
purposes and you use it at your own risk. I do not take responsibility if you
screw something up. Use common sense, do not 'rm -rf /' as root for example.
If you have any questions then do not hesitate to contact me.
See https://raymii.org/s/static/About.html for details.