MYSQL ERROR 2003 (HY000): Can't connect to MySQL server on '192.168.10.210' (111) 解決方法

今天在測試MySQL的連接時候，發現連接不通過，並報錯ERROR 2003 (HY000): Can't connect to mysql server on '192.168.10.210' (111) 
測試代碼：

require 'mysql2'
client = Mysql2::Client.new(:host=>"192.168.10.210",:username=>'root',:password=>"root")
puts results = client.query("show databases;")

谷歌了一下之后，原來是在mysql的my.cnf中有下面一段代碼：

# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
bind-address           = 127.0.0.1  #這里默認監聽本地localhost

如果要讓mysql監聽到其他的地址，可以將bind-address = 127.0.0.1注釋掉。 
或者將bind-address = 0.0.0.0監聽所有的地址

屏蔽掉之后再次運行代碼又出現：Host '192.168.10.83' is not allowed to connect to this MySQL server 
 
解決方法： 
如果想讓192.168.10.83能夠連接到本地的這個數據庫，要讓數據庫給其分配權限,登錄mysql，執行:(username 和 password是登錄mysql的用戶名和密碼)

GRANT ALL PRIVILEGES ON *.* TO 'username'@'192.168.10.83' IDENTIFIED BY 'password' WITH GRANT OPTION;

如果要想所有的外部ip地址都能夠訪問使用mysql，可以執行下面：

GRANT ALL PRIVILEGES ON *.* TO 'username'@'%' IDENTIFIED BY 'password' WITH GRANT OPTION;

之后執行刷新數據庫：

flush privileges;

如果要查看用戶的權限，可以執行：

> show grants for 'root'@192.168.10.83