Например, из заголовков ответа апача
$ telnet ya.ru 80
Trying 213.180.194.129...
Connected to ya.ru.
Escape character is '^]'.
HEAD / HTTP/1.0
HTTP/1.1 200 OK
Date: Wed, 19 Nov 2003 14:54:02 GMT
Server: Apache/1.3.6 (Unix) PHP/4.0.1pl2 mod_perl/1.19 rus/PL28.15
Set-Cookie: yandexuid=9487411069253642; path=/; domain=.yandex.ru; expires=Friday, 31-Dec-10 23:59:59 GMT
Cache-Control: max-age=300, private
Expires: Wed, 19 Nov 2003 14:59:02 GMT
Connection: close
Content-Type: text/html; charset=windows-1251
Connection closed by foreign host.
$