ci sessions user_data disappears

[eluser]Miky llanderal[/eluser]
i read more about this and i put http://127.0.0.1/ in cookie domain but still wrong, i think that my problem may be the cookie, maybe the session doesn't find the cookie and that is why it starts other session .... but i don know how to fix this, i dont know how to set a cookie correctly in localhost enviroment,