Rails
Rails5

rails s で起動できません。

takuminoMacBook-Pro:sample takumi$ rails s
=> Booting Puma
=> Rails 5.0.6 application starting in development on http://localhost:3000
=> Run rails server -h for more startup options
Puma starting in single mode...
* Version 3.10.0 (ruby 2.3.1-p112), codename: Russell's Teapot
* Min threads: 5, max threads: 5
* Environment: development
* Listening on tcp://0.0.0.0:3000
Use Ctrl-C to stop

どのようにしたら良いでしょうか?