How to use Gnus to read newsgroup like gnu.emacs.gnus?

[tuhdo1710]

I tried the following code:

(setq user-mail-address "tuhdo1710@gmail.com")
(setq user-full-name "Tu, Do")
(setq gnus-select-method '(nntp "gnu.emacs.gnus"))

But it didn't work. Gnus gave me error:

>>> (error gnu.emacs.gnus/nntp Name or service not known)
nntp (gnu.emacs.gnus) open error: '>>> (error gnu.emacs.gnus/nntp Name or 
service not known)'.  Continue? (y or n) n
Couldn't open server on gnu.emacs.gnus

Thanks.