gistfile1.rb

#Sinatra server
require 'rubygems'
require 'sinatra'

post '/upload' do
  filename = "./uploaded/" + Time.now.to_i.to_s + ".gsm"
  FileUtils.mv params[:data][:tempfile].path, filename
  "Received #{File.size filename} bytes and saved as #{filename} for user #{params[:user_id]}"
end

gistfile2.rb

require 'rubygems'
require 'curb'

url = 'http://localhost:4567/upload'
c = Curl::Easy.new url

c.multipart_form_post = true

c.http_post Curl::PostField.file('data', './to_upload/tt-monkeys.gsm'), Curl::PostField.content('user_id', '1')
                     
p c.body_str

gistfile3.txt

#Returns
ruby upload_client.rb 
"Received 26697 bytes and saved as ./uploaded/1246337343.gsm for user 1"