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linuxtcpdebian

How can I find a process using a TCP port?

After starting an HTTP server process a couple of times, I get this error like an instance of Go has not stopped!?

listen tcp :9000: bind: address already in use

I have experienced something like this with Node.js too, but I was able to kill the process.. Unfortunately it seems like I can't find the process id and kill it..

How can I "free" the TCP port?

Solution

  • If you are on Unix-like system, you can use netstat to find out which process is listening on a port:

    sudo netstat -nlp | grep 9000

    It turns out the -p option is not available on OS X. If you are using OS X, you can do this:

    lsof -n -i4TCP:$PORT | grep LISTEN

    Who is listening on a given TCP port on Mac OS X?