Thanks to all of you.
    I can connect to MySQL using MySQL command-line program.
    The problem seems having been resolved , yet not completely. I logined as super user "ygx" other than "root". And "FreeRADIUS гл MySQL" works again. I didnt make any other changes except editing sql.conf to login as user "ygx".
    The problem maybe exist in the table "user " of the database "mysql", which is as follow:
mysql> select Host,User,Password from user;
+-------------------------------+--------+-----------------------------------------------------------------------------------+
| Host           | User |                                    Password                                  |
+-------------------------------+--------+-----------------------------------------------------------------------------------+
| localhost    | root    |    *639C78D0EC361EE7FBD5E7B2EE7D4356079DB335 |
| 202.117.54.251 | root    |    *639C78D0EC361EE7FBD5E7B2EE7D4356079DB335 |
| %                | ygx    |     * 95FF347796503B19B351447515672881EB314534     |
| %                            | root    |    *81F5E21E35407D884A6CD4A731AEBFB6AF209E1B |
+------------------------------+---------+-----------------------------------------------------------------------------------+
Note that user 'root' has different Password .

Regards
Guoxian.

2007/5/15, Alan Dekok <aland@deployingradius.com >:

yao guoxian wrote:
...
>   rlm_sql_mysql: Couldn't connect socket to MySQL server
> root@202.117.54.251:radius
>   rlm_sql_mysql: Mysql error 'Access denied for user
> 'root'@'202.117.54.251'

  Can you connect from that IP to MySQL using the MySQL command-line
program?  If not, check the ACL's on the machine running MySQL.

  Alan DeKok.
--
  http://deployingradius.com       - The web site of the book
   http://deployingradius.com/blog/ - The blog
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