ruby-on-rails - Railsサーバーを実行すると、次のエラーが表示されます

Question

WARNING: Nokogiri was built against LibXML version 2.8.0, but has dynamically loaded 2.7.3
=> Booting WEBrick
=> Rails 3.2.3 application starting in development on `http://0.0.0.0:3000`
=> Call with -d to detach
=> Ctrl-C to shutdown server
Exiting
/opt/local/lib/ruby1.9/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/connection_adapters/postgresql_adapter.rb:1194:in `initialize': could not connect to server: Connection refused (PG::Error)
    Is the server running on host "localhost" and accepting
    TCP/IP connections on port 5432?
could not connect to server: Connection refused
    Is the server running on host "localhost" and accepting
    TCP/IP connections on port 5432?

psql -h localhost を実行すると、次のようになります。

psql: could not connect to server: Connection refused
    Is the server running on host "localhost" and accepting
    TCP/IP connections on port 5432?

私のシステム設定: Mac OSX 10.7.5 で、すべてが Macports でインストールされました。