ruby script to serial port

serial.rb

require 'rubygems'
require 'serialport'

begin

        parameters = {"baud" => 19200, "data_bits" => 8, "stop_bits"=>1,"parity"=>SerialPort::NONE}

        comm_port = '/dev/tty.usbmodem411'

        sp = SerialPort.new(comm_port, parameters)

        #sp.read_timeout = 1000
        #sp.write_timeout = 1000

        sp.write "AT+CPIN?\r\n"
        puts sp.read

rescue
        puts "Error: #{$!}"
        sp.close
end