MySQL 连接适用于 localhost 但不适用于 127.0.0.1

Question

我在 Debian Wheezy ( apt-get install mysql-server mysql-client)上有一个非常标准的 MySQL 安装，我之前已经成功完成了很多次。

当我尝试通过 连接时localhost，一切正常。但是连接通过127.0.0.1给出错误消息：

$ mysql -h localhost -P 3306 -u xxx -p
-- works

$ mysql -h 127.0.0.1 -P 3306 -u xxx -p
ERROR 2013 (HY000): Lost connection to MySQL server at 'reading initial communication packet', system error: 0

当我尝试从 Java 应用程序连接时，我得到了类似的错误，尽管我使用的localhost是主机名：

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure. The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
Caused by: java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.

当 MySQL 服务器关闭空闲连接或重新启动时，我通常会收到此异常。但是，这会在应用程序首次尝试连接时在应用程序启动时发生。

有趣的是，这在几个小时前确实有效。不幸的是，我不记得在服务器上做过任何更改。:-(

所以说实话，这篇文章包含两个问题：为什么我不能通过 连接127.0.0.1？为什么我的应用程序localhost不能通过 CLI连接，但我可以通过 CLI 连接？

# mysqld -V
mysqld  Ver 5.5.37-0+wheezy1-log for debian-linux-gnu on x86_64 ((Debian))

# mysql -V
mysql  Ver 14.14 Distrib 5.5.37, for debian-linux-gnu (x86_64) using readline 6.2

# grep bind /etc/mysql/my.cnf
bind-address = 127.0.0.1

# grep socket /etc/mysql/my.cnf
socket = /var/run/mysqld/mysqld.sock

# ping localhost
PING localhost (127.0.0.1) 56(84) bytes of data.
64 bytes from localhost (127.0.0.1): icmp_req=1 ttl=64 time=0.022 ms

# grep localhost /etc/hosts
127.0.0.1 localhost
::1     ip6-localhost ip6-loopback

# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination
ACCEPT     tcp  --  anywhere             anywhere             tcp

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

# netstat -ln | grep 3306
tcp        0      0 127.0.0.1:3306          0.0.0.0:*               LISTEN

tomcat # grep mysql conf/server.xml
driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost:3306/dbname"

编辑

我尝试将服务器绑定到0.0.0.0和::，但无济于事。

服务器支持 IPv6 并进行了相应配置：

# host localhost
localhost has address 127.0.0.1
localhost has IPv6 address ::1

当我尝试连接到::1.

# ping6 ::1
64 bytes from ::1: icmp_seq=1 ttl=64 time=0.020 ms

# ping6 localhost
64 bytes from ip6-localhost: icmp_seq=1 ttl=64 time=0.018 ms

编辑 2

连接通过telnet提供的信息不多，但显示连接立即关闭。

# telnet localhost 3306
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Connection closed by foreign host.

顺便说一句，即使启用了日志记录，MySQL 日志文件也是完全无声的。

Answer 1

这个问题与MySQL无法连接通过“localhost”非常相似，只有127.0.0.1。正如此处所述，您可能将 MySQL 配置为仅侦听网络套接字而不侦听文件系统套接字。