The way I did it ...

multiprocess_stom_publisher.rb

@files = ARGV
@files.each_with_index do |file, index|
  pid = fork {
    require 'stomp'
    client = Stomp::Client.open("", "", "localhost", 61613)

    def send_message(server, message, queue)
      server.send("/cdr/cdr#{queue}", message, {})
    end

    file = File.open(file, 'r')
    while !file.eof? do
      offset = file.read(2).unpack('S')[0].to_i
      message = file.read(offset)
      send_message(client, message, index)
    end
  }
  instance_variable_set("@pid_#{index}".to_sym, pid)
  Process.waitpid(instance_variable_get("@pid_#{index}".to_sym), Process::WNOHANG)
end