Using HTTP as Transport in RPC System (Server)

http_server.rb

#!/usr/bin/env ruby
require 'sinatra'
require './calculator'

calculator = Calculator.new

post '/calc' do
  req = JSON.parse(request.body.read)

  # call a method on the calculator instance, passing along params
  args   = req['params'].unshift(req['method'])
  result = calculator.send *args

  # HTTP stuff
  status 200
  headers 'Content-Type' => 'application/json'

  # make sure to encode response as JSON
  JSON.generate({
    'id' => req['id'],
    'result' => result,
    'jsonrpc' => '2.0'
  })
end