The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.

某天升级mysql数据库程序发现报错The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.，

发现登陆用户、密码正确，连接池正确，mysql运行正确。最后把localhost修改成127.0.0.1即jdbc:mysql://127.0.0.1:3306/cookqq 为什么呢？？？看看下面分析

研究过程（1）jdbc:mysql://127.0.0.1:3306/cookqq 数据库驱动连接地址，重要的信息是ip+端口号

（2）3306端口号没有问题

（3）数据库cookqq也存在

（4）那就是location这个地址，mysql没有识别，为什么没有识别呢

（5）127.0.0.1/8整个都是环回地址，用来测试本机的TCP/IP协议栈，发往这段A类地址数据包不会出网卡，网络设备不会对其做路由。

（6）localhost=127.0.0.1，只不过localhost是域名，127.0.0.1是IP地址。一般系统都默认将localhost映射到127.0.0.1地址上

    在 Windows 中，这个域名是预定义的，从 hosts 文件中可以看出：

 # localhost name resolution is handled within DNS itself.#
        127.0.0.1       localhost#::1

    localhost而在 Linux 中，其定义位于 /etc/hosts 中：

    127.0.0.1    localhost

（7）原来是这个原因。也就是localhost只是一个普通域名，如果你映射到127.0.0.1，就能找到本机

如果你去掉localhost这个域名，或者把localhost映射到其他的地址上，mysql首先获取localhost，然后拿localhost去hosts文件去找相应的ip，找到就正确返回，找不到就报错 

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.

at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

at java.lang.reflect.Constructor.newInstance(Constructor.java:526)

at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)

at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)

at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:348)

at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2391)

at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2428)

at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2213)

at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:797)

at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)

at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

at java.lang.reflect.Constructor.newInstance(Constructor.java:526)

at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)

at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:389)

at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)

at java.sql.DriverManager.getConnection(DriverManager.java:571)

at java.sql.DriverManager.getConnection(DriverManager.java:215)