class DEBUGGER__::UI_ServerBase

def process
  while true
    DEBUGGER__.debug{ "sleep IO.select" }
    _r = IO.select([@sock])
    DEBUGGER__.debug{ "wakeup IO.select" }
    line = @session.process_group.sync do
      unless IO.select([@sock], nil, nil, 0)
        DEBUGGER__.debug{ "UI_Server can not read" }
        break :can_not_read
      end
      @sock.gets&.chomp.tap{|line|
        DEBUGGER__.debug{ "UI_Server received: #{line}" }
      }
    end
    return unless line
    next if line == :can_not_read
    case line
    when /\Apause/
      pause
    when /\Acommand (\d+) (\d+) ?(.+)/
      raise "not in subsession, but received: #{line.inspect}" unless @session.in_subsession?
      if $1.to_i == Process.pid
        @width = $2.to_i
        @q_msg << $3
      else
        raise "pid:#{Process.pid} but get #{line}"
      end
    when /\Aanswer (\d+) (.*)/
      raise "not in subsession, but received: #{line.inspect}" unless @session.in_subsession?
      if $1.to_i == Process.pid
        @q_ans << $2
      else
        raise "pid:#{Process.pid} but get #{line}"
      end
    else
      STDERR.puts "unsupported: #{line.inspect}"
      exit!
    end
  end
end