禁止以ip方式访问网站

好比192.168.16.116是个人服务器地址，域名是www.demo.com，我想只容许用户经过域名访问，而不容许用户经过ip访问，全部经过ip访问的都跳转到域名，第一个server部分为起做用的配置代码

 

nginx配置以下：

server {
        server_name 80 default;
        server_name _;
        rewrite ^(.*) http://www.demo.com;
        }

server {

        server_name localhost www.demo.com;

        root /usr/share/nginx/www;
        index index.html index.htm;

        location / {
                index index.php;
                try_files $uri $uri/ /index.html;
        }

        # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
        #
        location ~ \.php$ {

                fastcgi_pass unix:/var/run/php5-fpm.sock;
                fastcgi_index index.php;
                include fastcgi_params;
        }

}