redis_on_tcp.rb

require 'socket'

class RedisService

  attr_accessor :host, :port
  LINE = "\r\n"

  def initialize(host, port, password: nil)
    @host = host
    @port = port
    @password = password
  end

  def send(key, val)
    open_socket
    mes = create_message(key: key, val: val, command: 'set')
    send_to_redis(mes)
  ensure
    close_socket
  end

  def get(key)
    open_socket
    mes = create_message(key: key, command: 'get')
    send_to_redis(mes)
  ensure
    close_socket
  end

  private

  def send_to_redis(mes)
    if @password
      mes = create_message(command: 'auth', val: @password) + mes
    end
    sleep(1)
    @socket.puts(mes)
    sleep(1)
    response = @socket.read
    response.chomp!(LINE)
    resp_arr = response.split(LINE)
    if @password
      return resp_arr[2] if resp_arr[0].eql?('+OK')
      return resp_arr[0]
    end
    resp_arr[1]
  end

  def create_message(key: nil, val: nil, command: 'set')
    arr = []
    arr << respialize_string(command)
    arr << respialize_string(key) if key
    arr << respialize_string(val) if val
    "*#{arr.count}" + LINE + arr.join(LINE) + LINE
  end

  def respialize_string(str, bulk = false)
    return "$#{str.to_s.bytesize}#{LINE}+#{str}" if bulk
    
    "$#{str.to_s.bytesize}#{LINE}#{str}" 
  end

  def open_socket
    @socket = TCPSocket.open(host, port)
  end

  def close_socket
    @socket && @socket.close
  end
end