HowTo: Kill TCP Connections in CLOSE_WAIT State

HowTo: Kill TCP Connections in CLOSE_WAIT State

 

If you are seeing a large number of connections persisting in CLOSE_WAIT state, it’s probably a problem with the application itself.

Restarting it will clear the connections temporarily, but obviously, further investigation will be required to find the cause of the problem.

If restarting of application is undesirable, you can manually kill all connections that are in CLOSE_WAIT state.

Kill CLOSE_WAIT connections by IP

Kill TCP connections in CLOSE_WAIT state, established with the foreign IP address 192.168.0.100:

$ netstat -anp |\
grep 192.168.0.100 |\
grep CLOSE_WAIT |\
awk '{print $7}' |\
cut -d \/ -f1 |\
grep -oE "[[:digit:]]{1,}" |\
xargs kill

The same command in one line:

$ netstat -anp | grep 192.168.0.100 | grep CLOSE_WAIT | awk '{print $7}' | cut -d \/ -f1 | grep -oE "[[:digit:]]{1,}" | xargs kill

Kill CLOSE_WAIT connections by PORT

Use the following command to Kill TCP connections in CLOSE_WAIT state on port 80:

$ netstat -anp |\
grep ':80 ' |\
grep CLOSE_WAIT |\
awk '{print $7}' |\
cut -d \/ -f1 |\
grep -oE "[[:digit:]]{1,}" |\
xargs kill

The same command in one line:

$ netstat -anp | grep ':80 ' | grep CLOSE_WAIT | awk '{print $7}' | cut -d \/ -f1 | grep -oE "[[:digit:]]{1,}" | xargs kill

Kill CLOSE_WAIT connections by IP and PORT

Kill TCP connections in CLOSE_WAIT, state established with foreign IP address 192.168.0.100 on port 80:

$ netstat -anp |\
grep 192.168.0.100 |\
grep ':80 ' |\
grep CLOSE_WAIT |\
awk '{print $7}' |\
cut -d \/ -f1 |\
grep -oE "[[:digit:]]{1,}" |\
xargs kill

The same command in one line:

$ netstat -anp | grep 192.168.0.100 | grep ':80 ' | grep CLOSE_WAIT | awk '{print $7}' | cut -d \/ -f1 | grep -oE "[[:digit:]]{1,}" | xargs kill

How Does It Work?

$ netstat -anp |\  # print network connections
grep 192.168.0.100 |\  # established with IP 192.168.0.100
grep ':80 ' |\  # established on port 80
grep CLOSE_WAIT |\  #  connections in CLOSE_WAIT state
awk '{print $7}' |\  #  print the 7th column
cut -d \/ -f1 |\  #  extract PIDs
grep -oE "[[:digit:]]{1,}" |\  #  extract PIDs
xargs kill  #  kill PIDs

lsof -i :80 |grep CLOSE_WAIT| awk '{print $2}|uniq| xargs kill
 
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