api.rb

require 'sinatra/base'

class Robut::API < Sinatra::Base
  set :server, 'thin'
  set :connections, []
  set :logging, false

  get '/logs', provides: 'text/event-stream' do
    stream :keep_open do |out|
      settings.connections << out
      out.callback { settings.connections.delete(out) }
    end
  end

  post '/input' do
    settings.connections.each { |out| out << "#{params[:log]}\n" }
    204
  end
end

error

/Users/user/.rvm/gems/ruby-2.2.2/gems/sinatra-1.4.4/lib/sinatra/base.rb:1764:in `detect_rack_handler': Server handler (thin) not found. (RuntimeError)
	from /Users/.rvm/gems/ruby-2.2.2/gems/sinatra-1.4.4/lib/sinatra/base.rb:1420:in `run!'
	from ./bin/robut:15:in `<main>'