Troubleshooting sockets with ss
Connection State
You can use the --query
or -A
query addition to dump a sockets table. The magic word autobound
checks for ephemeral ports that sockets have attached themselves to. Prepare yourself for screeds of output, even on a quiet system. An abbreviated version of the output is shown in Listing 8.
Listing 8
ss -a -A all autobound
You can also filter by TCP states; for instance, the following command filters for sFTP traffic:
# ss state connected dport = :sftp
Anything treated as "current" in relation to the sFTP port is displayed promptly.
You can complicate the command a little more with a boolean operator:
# ss ( sport = :ftp or dport = :http )
You can even use ss to find connections that are in a specific TCP state, including the established
, syn-sent
, syn-recv
, fin-wait-1
, fin-wait-2
, time-wait
, closed
, close-wait
, last-ack
, listen
, and closing
.
The TCP state parameters let you do some very powerful querying. For example, checking for FIN--WAIT--1 states lets you identify whether your application has closed its side of a connection, but a remote host has not closed its side, thus tying up your machine's precious ports:
ss -o state fin-wait-1 '( sport = \ :ftp or sport = :http )' \ dst 10.10.3.3/24:22
Sso It Ends
The ss utility is a powerful tool that will help you query your network in significant detail. Ss is extremely high performance for both manual and automated queries, and it requires very few keystrokes to execute common commands.
This tiny but heroic tool helps flex the muscles of any sys admin. If you want to increase the power of your admin toolkit, try practicing some of the more complex commands in your day-to-day work.
« Previous 1 2 3
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
Endless OS 6 has Arrived
After more than a year since the last update, the latest release of Endless OS is now available for general usage.
-
Fedora Asahi 40 Remix Available for Macs with Apple Silicon
If you've been anticipating KDE's Plasma 6 for your Apple Silicon-powered Mac, then you're in luck.
-
Red Hat Adds New Deployment Option for Enterprise Linux Platforms
Red Hat has re-imagined enterprise Linux for an AI future with Image Mode.
-
OSJH and LPI Release 2024 Open Source Pros Job Survey Results
See what open source professionals look for in a new role.
-
Proton 9.0-1 Released to Improve Gaming with Steam
The latest release of Proton 9 adds several improvements and fixes an issue that has been problematic for Linux users.
-
So Long Neofetch and Thanks for the Info
Today is a day that every Linux user who enjoys bragging about their system(s) will mourn, as Neofetch has come to an end.
-
Ubuntu 24.04 Comes with a “Flaw"
If you're thinking you might want to upgrade from your current Ubuntu release to the latest, there's something you might want to consider before doing so.
-
Canonical Releases Ubuntu 24.04
After a brief pause because of the XZ vulnerability, Ubuntu 24.04 is now available for install.
-
Linux Servers Targeted by Akira Ransomware
A group of bad actors who have already extorted $42 million have their sights set on the Linux platform.
-
TUXEDO Computers Unveils Linux Laptop Featuring AMD Ryzen CPU
This latest release is the first laptop to include the new CPU from Ryzen and Linux preinstalled.