Sylwia Vargas
Posted on • Updated on
#beginners #codenewbie #todayisearched
This is a thing I need to google every now and then so here's a simple recipe for closing neglected ports on MacOS, Windows and Linux.
Here are the steps:
1. Find the process ID (PID) of the port (replace the 'portNumber' with the number)
sudo lsof -i :portNumber
This will give you a response as follows — copy the PID number for the next step:
2. Kill the process
First, try this (replace PID with the number you copied above):
kill PID
Now, test if it's closed by connecting to the port (replace portNumber with the actual port number):
nc localhost portNumber
If it returns immediately with no output, the port isn't open. However, if it returns some input, try to kill it with:
kill -9 PID
Again, try to connect. If it's still running, try this:
sudo kill -9 PID
Here are the steps for Windows:
1. Find the process ID (PID) of the port (replace the 'portNumber' with the number)
netstat -ano | findstr :portNumber
Copy the PID number for the next step.
2. Kill the process
First, try this (replace typeyourPIDhere with the number you copied above):
taskkill /PID typeyourPIDhere /F
Run the first command again to see if it's closed.
Here are the steps for Linux (courtesy of mayankjoshi)
1. Get a list of all open processes
$top
2. Kill a process
kill pid kills the process by process idkillall pname kills the process by name-9 for forceful killing in both kill and killall
Use sudo if it's a root process.
Top comments (23)
Subscribe
CapSel
CapSel
Nothing worth mentioning upfront.
-
Location
Poland
-
Work
Do I need a title? at I don't want to give a company name
-
Joined
• Mar 31 '20
- Copy link
Do not use lsof on live Linux (and possibly FreeBSD) servers. In very rare conditions it can cause entire server to hang - hardware reboot needed.
Instead use ss (fast!) and if you really have to then netstat (sloooww, cpu hog).
Sylwia Vargas
Sylwia Vargas
I'm a tech writer and educator advocating for code newbies ✨ I'm also a Developer Relations Lead + front-end dev at @inngest
-
Location
New York
-
Pronouns
she/her
-
Joined
• Mar 31 '20
- Copy link
Thank you! I don't think I propose it in the post 🤔
What do you think about the steps proposed by mayankjoshi that I integrated into the blog post:
- Get a list of all open processes
$top- Kill a process
kill pidkills the process by process idkillall pnamekills the process by name-9for forceful killing in both kill and killallUsesudoif it's a root process.
Would you add anything?
CapSel
CapSel
Nothing worth mentioning upfront.
-
Location
Poland
-
Work
Do I need a title? at I don't want to give a company name
-
Joined
• Mar 31 '20
- Copy link
ss -tnlp and netstat -tnlp shows pid of processes, their names and their open/listening (aka server) ports. There are tons of tutorials @google about these two commands. top on the other hand does not show open ports. Depending on the OS it can have some shortcuts to kill.
As to root and sudo I would be very careful. You may end up with a surprise ;) You can kill some system service like X server, print spooler, OS upgrade process.
kill (pid) and killall (matching a name) sends signals to processes. Without a name of a signal given default one is used - SIGTERM. This is just "asking" process to exit - similar to alt+f4. The -9 signal is a SIGKILL signal - usually just called kill. It cannot be ignored by processes.
After killing process that had opened TCP port it make take a while before this port is closed. It hangs in OS in special state - only thing you can do is wait or reboot.
Sooner or later you're going to need kill some process to free some port. It's a good idea to glance some docs/manuals (man ss, man netstat) to have some vague memories about what each of these commands can do. Every command is useful. Everyone has their favourite set. Do an experiment - but before you do save your files.
Tisha Murvihill
Tisha Murvihill
-
Joined
• Oct 22 '22
- Copy link
just wanted to say thanks for the info :)
Richard Herbert
Richard Herbert
-
Joined
• Mar 30 '20
- Copy link
I always have an issue with port 80. The macOS just doesn't want to let it go for non-root users.
Do you have any further suggestions as your script doesn't seem to work for me.
Sylwia Vargas
Sylwia Vargas
I'm a tech writer and educator advocating for code newbies ✨ I'm also a Developer Relations Lead + front-end dev at @inngest
-
Location
New York
-
Pronouns
she/her
-
Joined
• Mar 30 '20
- Copy link
Yeah. I had a port 80 problem when Dropbox was running in the background. As soon as I changed that (i.e. now Dropbox only runs when I open it instead of when I switch the laptop on), my problem was fixed. You can see what occupies your port 80 by running sudo lsof -i :YourPortNumber.
changing your root permissions? unix.stackexchange.com/questions/1...
Richard Herbert
Richard Herbert
-
Joined
• Mar 30 '20
- Copy link
Yes, I've tried the DropBox trick but still macOS won't let my process use port 80 unless I start that process as root.
Not sure how that link you offered helps?
Sylwia Vargas
Sylwia Vargas
I'm a tech writer and educator advocating for code newbies ✨ I'm also a Developer Relations Lead + front-end dev at @inngest
-
Location
New York
-
Pronouns
she/her
-
Joined
• Mar 30 '20
- Copy link
Eh how annoying. Well you could add root permissions to other users and then you should be able to close the port.
Richard Herbert
Richard Herbert
-
Joined
• Mar 30 '20
- Copy link
Ah, is that what that link was about?
Sylwia Vargas
Sylwia Vargas
I'm a tech writer and educator advocating for code newbies ✨ I'm also a Developer Relations Lead + front-end dev at @inngest
-
Location
New York
-
Pronouns
she/her
-
Joined
• Mar 30 '20
- Copy link
Exactly :)
Richard Herbert
Richard Herbert
-
Joined
• Mar 30 '20
- Copy link
Okay, I’ll take a closer look and let you know how I get on.
Thanks for your help.
Richard Herbert
Richard Herbert
-
Joined
• Mar 31 '20
- Copy link
@sylwia - That link seemed to be about file permissions rather than process permissions.
See my reply to Mateusz where I use the insight provided and find my solution,
Mateusz Jarzyna
Mateusz Jarzyna
-
Location
Poland
-
Joined
• Mar 31 '20
- Copy link
I’s standard, security behavior. You cannot open port <1024 as standard user, you need root permision on both macOS and Linux systemy. Because of security.
When someone will hack into your server, the hacker cannot kill your HTTP server and run phishing site on you domain because he need root privilages.
Richard Herbert
Richard Herbert
-
Joined
• Mar 31 '20
- Copy link
Well, that makes sense.
Armed with this knowledge I researched port forwarding and discovered pf (packet filtering) which lead me to salferrarello.com/mac-pfctl-port-f... which was the answer to my issue.
Thanks for the insight!
mayank joshi
mayank joshi
I love system design and most of the time I find myself learning or designing one of them........I am a moderator at Dev.to 😀
-
Email
-
Location
Global
-
Education
NIT Bhopal
-
Joined
• Mar 31 '20
- Copy link
In Linux
$top to see the list of open process
Killing a process
kill pid
- kills the process by process id
killall pname
- kills the process by name
-9 for forceful killing in both kill and killall
Use sudo if it's a root process.
Sylwia Vargas
Sylwia Vargas
I'm a tech writer and educator advocating for code newbies ✨ I'm also a Developer Relations Lead + front-end dev at @inngest
-
Location
New York
-
Pronouns
she/her
-
Joined
• Mar 31 '20
- Copy link
Thank you! I'll add it right away!
mayank joshi
mayank joshi
I love system design and most of the time I find myself learning or designing one of them........I am a moderator at Dev.to 😀
-
Email
-
Location
Global
-
Education
NIT Bhopal
-
Joined
• Mar 31 '20
- Copy link
Actually the URL to my profile is incorrect.😅😅
Sylwia Vargas
Sylwia Vargas
I'm a tech writer and educator advocating for code newbies ✨ I'm also a Developer Relations Lead + front-end dev at @inngest
-
Location
New York
-
Pronouns
she/her
-
Joined
• Mar 31 '20
- Copy link
🤦♀️corrected!
Lajos Koszti
Lajos Koszti
-
Joined
• Mar 31 '20
- Copy link
It's not closing a port, but stopping a process. You close ports using firewall usually.
mayank joshi
mayank joshi
I love system design and most of the time I find myself learning or designing one of them........I am a moderator at Dev.to 😀
-
Email
-
Location
Global
-
Education
NIT Bhopal
-
Joined
• Mar 31 '20
- Copy link
When a process is killed, the ports are automatically Freed.
When I was doing TCP up connection I Freed same port for reuse using this method itself.
Lajos Koszti
Lajos Koszti
-
Joined
• Mar 31 '20 • Edited on Mar 31 • Edited
- Copy link
Luckily, if you stop the application, the port will be released. The title says How to properly close a port?, not how to kill a process. What if you want the keep the process running but don't want to listen on that port anymore?
mayank joshi
mayank joshi
I love system design and most of the time I find myself learning or designing one of them........I am a moderator at Dev.to 😀
-
Email
-
Location
Global
-
Education
NIT Bhopal
-
Joined
• Mar 31 '20
- Copy link
I don't think it is possible to free a port held by a process without killing the same process.
Sylwia Vargas
Sylwia Vargas
I'm a tech writer and educator advocating for code newbies ✨ I'm also a Developer Relations Lead + front-end dev at @inngest
-
Location
New York
-
Pronouns
she/her
-
Joined
• Mar 31 '20
- Copy link
Sure. I decided for this title because that's what my students google — the post is in my budding series primarily for my students at a coding bootcamp ❤️
View full discussion (23 comments)
For further actions, you may consider blocking this person and/or reporting abuse
