app.rb

require "sinatra"

configure do
  enable :sessions
  set :bind, '0.0.0.0'
end


get "/" do
  erb :index
end

post "/" do
  session[:data] = {"one"=>"a", "two"=>"a"} #params.inspect
  p session
  params.inspect
end

get "/values" do
  session[:data]
end

index.erb

<form name="test" action="/" method="post">
  <input type="text" name="one" />
  <input type="text" name="two" />
  <input type="submit" value="submit"/>
</form>