How to set port for Rack app?

问题

builder.rb:

def app
  Rack::Builder.new do
    run App.new
  end.to_app
end

How to run on a given port?

回答1:

Try:

Rack::Handler.default.run(app, :Port => 3000)

Although it would be more typical to run your app in a config.ru file and specify port as a command line option to rackup, e.g.: rackup -p 3000.

回答2:

When you rackup just specify it with option -p so:

rackup -p 8808 would work just fine.

来源：https://stackoverflow.com/questions/32594945/how-to-set-port-for-rack-app