macos - Find (and kill) process locking port 3000 on Mac

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How do I find (and kill) processes
that listen to/use my tcp ports? I'm on mac os
x.

Sometimes, after a crash or some bug, my
rails app is locking port 3000. I can't find it using ps
-ef...

When
doing

rails
            server

I
get

Address
already in use - bind(2)
(Errno::EADDRINUSE)

2014
update:

To complete some of the answers below:
After executing the kill commands, deleting the pid file might be necessary
rm ~/mypath/myrailsapp/tmp/pids/server.pid

Answer

1. You can try
   netstat

   
   
   

   netstat
               -vanp tcp | grep
               3000
   




2. For
   macOS El Capitan and newer (or if your netstat doesn't
   support -p), use
   lsof

   
   
   
   

   sudo
               lsof -i tcp:3000
               
   




3. For
   Centos 7
   use

   
   
   

   netstat -vanp --tcp | grep
               3000