gistfile1.rb

require "active_support/all"
require "net/http"

token = "my_token"
url = "https://graph.facebook.com/v2.6/me/messages?"
sender = 100688998246663
text = "Hello"
request_params =  {
  recipient: {id: sender},
  message: {text: text},
  access_token: token
}

uri = URI.parse(url)

response = Net::HTTP.new(uri.host, uri.port)
http = Net::HTTP.new(uri.host, uri.port)
http.use_ssl = true
http.verify_mode = OpenSSL::SSL::VERIFY_NONE

request = Net::HTTP::Post.new(uri.path, initheader = {'Content-Type' =>'application/json'})
request.body = request_params.to_json

http.request(request)

response = http.request(request)