Finding which process is listening on a port

I’m known for having a lot of projects.

These days I have a day job, am trying to grind out more posts a
week on this blog, regularly write for, run
HolidayAPI and Ginpop and am currently on the “advisor track”
for Startup School with CrowdSync.

This list doesn’t even include some other stealth projects (more to come 😉 and
juggling being a husband and father!!

All of that said, running a lot of projects means forgetting that I already have
some code running locally that may conflict with another project.

These conflicts usually result in having one project’s code running in a Docker
container in a detached, probably unnamed, screen session.

Then I go and try to docker-compose up another project and Docker starts to
bark about how a port is in use by another process.

Wouldn’t it be nice if programs that try to listen to a power would tell you
what process is already running on the port?

It would be nice, but it’s not the case. This usually results in my doing a web
search for the 100th time on how to determine which process is listening on a
port so that I can track it down and kill the process without having to sift
through my active sessions.

Said web search usually leads me to a handful of articles that talk about how to
do it on Windows with netstat which I don’t even have installed.

Then eventually I find the right post on how to do things in Linux and I find
the PID and kill the process finally able to get back to work.

Turns out, this little problem doesn’t happen often enough for me to remember
which search result is the right one.

Tired of this dance, the other day I took a solution that uses ss which my
systems do have without any additional installation and turned it into a nice
little re-usable shell alias.

For those that aren’t aware, ss is “another utility to investigate sockets”.
It dumps socket statistics and is similar to netstat.

Using ss, I run the output through grep and cut to extract just the PID
for the process that’s listening on the port. I can then take that and do a
kill -9 on it and call it a day!

I called the shell function pp which stands for “PID Port”. Figured it would
be easy to remember and paired up well with ss.

The shell function is as follows:

# PID Port
function pp {
  ss -lptn sport = :$1 | grep -Eo 'pid=[0-9]+' | cut -c5-

And to use it, simply type pp followed by the port number. For example:

pp 3306 # MySQL's port if you have MySQL running
Josh Sherman - The Man, The Myth, The Avatar

About Josh

Husband. Father. Pug dad. Musician. Founder of Holiday API, Head of Engineering and Emoji Specialist at Mailshake, and author of the best damn Lorem Ipsum Library for PHP.

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