Rails 5.1 is a little different the pre 5.1
require 'rails/commands/server/server_command'
In rails 5.0 or below
require 'rails/commands/server'
# lib/host_and_port.rb
def __host_and_port__
options = Rails::Server::Options.new.parse!(ARGV)
options.values_at(:Host, :Port)
end
You can then find the host and port for various configuration files.
# config/initializers/carrier_wave.rb
require Rails.root.join('lib/host_and_port').to_s
CarrierWave.configure do |config|
config.asset_host = "http://" + __host_and_port__.join(":")
end
or
# config/environments/development.rb
require Rails.root.join('lib/host_and_port').to_s
host, port = __host_and_port__
config.action_mailer.default_url_options = { host: host, port: port }