WARN TCPServer Error: Address already in use - bind(2) Exiting Ruby on Rails

    This problem is due to port already used or not properly stopped. To work this properly first find the process id and then kill it and start the server again
    Follow the steps your output come like this:

    1. mohit@ubuntu:/home/app/alpha$ netstat -tulpn | grep :3000
    (Not all processes could be identified, non-owned process info
    will not be shown, you would have to be root to see it all.)
    tcp        0      0  *               LISTEN      8540/ruby
    2. mohit@ubuntu:/home/app/alpha$ kill -9 8540
    3. mohit@ubuntu:/home/app/alpha$ rails s
    => Booting WEBrick
    => Rails 3.0.11 application starting in development on
    => Call with -d to detach
    => Ctrl-C to shutdown server
    [2012-02-21 12:18:50] INFO  WEBrick 1.3.1
    [2012-02-21 12:18:50] INFO  ruby 1.9.2 (2011-07-09) [x86_64-linux]
    [2012-02-21 12:18:50] INFO  WEBrick::HTTPServer#start: pid=9210 port=3000
    Average: 5 (1 vote)