$('#' + file.id).attr('class', 'plupload_failed').find('a').css('display', 'block').attr('title', message);

alert(file.name + ' Uploading Failed due to server error');

I have found the error event, now how to reupload specific file.
just like
var retry = confirm('do you want to reupload flle?');
if(retry == true)
{
  $('#' + file.id).upload();
}

something like that