Freeing up a TCP/IP port?

Question

netstat -tulnap shows me what ports are in use. How to free up a port in Linux?

Solution 1

As the others have said, you'll have to kill all processes that are listening on that port. The easiest way to do that would be to use the fuser(1) command. For example, to see all of the processes listening for HTTP requests on port 80 (run as root or use sudo):

# fuser 80/tcp

If you want to kill them, then just add the -k option.

Solution 2

To kill a specific port in Linux use the below command

sudo fuser -k Port_Number/tcp

replace Port_Number with your occupied port.

Solution 3

In terminal type :

netstat -anp|grep "port_number"

It will show the port details. Go to last column. It will be in this format . For example :- PID/java

then execute :

kill -9 PID

For MAC:

lsof -n -i :'port-number' | grep LISTEN

Sample Response :

java   4744 (PID)  test  364u  IP0 asdasdasda   0t0  TCP *:port-number (LISTEN)

and then execute :

kill -9 PID 

Worked on Macbook

Solution 4

You can use tcpkill (part of the dsniff package) to kill the connection that's on the port you need:

sudo tcpkill -9 port PORT_NUMBER

Solution 5

To check all ports:

netstat -lnp

To close an open port:

fuser -k port_no/tcp

Example:

fuser -k 8080/tcp

In both cases you can use the sudo command if needed.

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Comments

[Matej]

I found that sending a request to the port also cleans it (i am no linux expert though)

[Korneel]

To install fuser on Debian: sudo apt-get install psmisc (bitflop.com/document/107)

[waqas]

shutting down a server machine is rare.

[Marlon Bernardes]

It worked, but I had to install psmisc too on CentOs 7 (sudo yum install psmisc)

[jplandrain]

did you get your "funniest" badge ?

[user1747935]

netstat -anp|grep <port> the last column has the process

[Anil Chahal]

No need for shutting down your computer.

[Valentin Roudge]

Best idea ever 10/10

[Hanynowsky]

kill -9 $(fuser 80/tcp 2>/dev/null)

[vinay chilakamarri]

This actually kills the process that opened the port and not the port itself.

[Anentropic]

unlike some of the other answers, this will surely work

[Anentropic]

this just hangs $ sudo tcpkill -9 port 5432 tcpkill: listening on lxcbr0 [port 5432]

[Anentropic]

obviously this doesn't work if the PID column is empty for that port

[Anentropic]

...and that happens if you don't have permission to see the process... try sudo netstat to actually see the PIDs :)

[vtechmonkey]

I was trying to kill a port on an amazon ec2 instance via putty cli. Forever said it had no processes running but the port(4200 for an angular app) was still open.This is the only command that worked for me.

[Owl]

BEWARE: fuser kills the process not the port. Which means if the port's stuck in limbo, can it work at all? This is not the right answer.

[Cadoiz]

Duplicate to the first two answers.

[Cadoiz]

This did not resolve my issue with ssh port forwarding. sudo fuser -k Port_Number/tcp did.