tcpserver error address already in use - bind(2) rails

blog2(master) ✗: rails s


=> Booting WEBrick
=> Rails 3.2.9 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
        SECURITY WARNING: No secret option provided to Rack::Session::Cookie.
        This poses a security threat. It is strongly recommended that you
        provide a secret to prevent exploits that may be possible from crafted
        cookies. This will not be supported in future versions of Rack, and
        future versions will even invalidate your existing user cookies.


        Called from: /Users/menxu/.rvm/gems/ruby-2.0.0-p0@blog2/gems/actionpack-3.2.9/lib/action_dispatch/middleware/session/abstract_store.rb:28:in `initialize'.
[2013-07-16 10:18:34] INFO  WEBrick 1.3.1
[2013-07-16 10:18:34] INFO  ruby 2.0.0 (2013-02-24) [x86_64-darwin12.2.1]
[2013-07-16 10:18:34] WARN  TCPServer Error: Address already in use - bind(2)

Exiting