However, with this change you will no longer be able to access the Rails server from a different machine, for example if your development environment is in a virtual machine and you would like to access it from the host machine. In such cases, please start the server with rails server -b 0.0.0.0 to restore the old behavior.
If you do this, be sure to configure your firewall properly such that only trusted machines on your network can access your development server.
如果你的 rails 是最新版本(4.2)你应该这样启动:rails server -b 0.0.0.0