SQLyog客户端无法连接MySQL服务器案例分析


--查看客户端ip [root@mysql ~]# w  22:20:43 up  2:39,  1 user,  load average: 0.00, 0.01, 0.05 USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT root     pts/1    192.168.1.7      21:35    3.00s  0.07s  0.01s w   --创建客户端用户 root@localhost 22:23:15[(none)]> create user 'zlm'@'192.168.1.7' identified by 'zlm';    Query OK, 0 rows affected (0.00 sec)    --用新创建的用户通过SQLyog客户端连接服务器
  提示无法连接，"Can't connect to MySQL server"   --创建服务器上的本地账户 root@localhost 22:34:26[(none)]> create user 'zlm'@'192.168.1.11' identified by 'zlm'; Query OK, 0 rows affected (0.00 sec)   root@localhost 22:34:29[(none)]> exit Bye   --测试是否可以连接 [root@mysql ~]# mysql --protocol=tcp -P 3306 -h192.168.1.11 -uzlm -pzlm Welcome to the MySQL monitor.  Commands end with ; or \g. Your MySQL connection id is 19 Server version: 5.5.39-log MySQL Community Server (GPL)   Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.   Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners.   Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.   zlm@192.168.1.11 22:44:52[(none)]> exit Bye   [root@mysql ~]# netstat -nalp | grep "3306"  tcp        0      0 0.0.0.0:3306                0.0.0.0:*                   LISTEN      3645/mysqld         tcp        0      0 192.168.1.11:3306           192.168.1.7:59783           ESTABLISHED 3645/mysqld         tcp        0      0 192.168.1.11:3306           192.168.1.7:59779           ESTABLISHED 3645/mysqld         [root@mysql ~]# netstat -nalp|grep "3306"|awk '{print $5}'|awk -F: '{print $1}'|sort |uniq -c|sort -nr       2 192.168.1.7
      1 0.0.0.0 [root@mysql ~]#    本地用户可以用3306端口连接，说明网络没有问题，3306端口也开启着，其实问题还是出在iptables 刚才用chkconfig iptables off来关闭各终端的iptables需要重启后才生效，此时并未重启过   [root@mysql ~]# chkconfig iptables --list iptables        0:off   1:off   2:on    3:on    4:on    5:on    6:off [root@mysql ~]# chkconfig iptables off [root@mysql ~]# chkconfig iptables --list iptables        0:off   1:off   2:off   3:off   4:off   5:off   6:off   --不重启直接关闭iptables服务 [root@mysql ~]# /etc/init.d/iptables stop iptables: Setting chains to policy ACCEPT: filter          [  OK  ] iptables: Flushing firewall rules:                         [  OK  ] iptables: Unloading modules:                               [  OK  ] [root@mysql ~]# /etc/init.d/iptables status iptables: Firewall is not running.     --关闭iptables后，再次连接成功  
  如果不想关iptables也可以，把-A INPUT -m state --state NEW -m tcp -p tcp --dport 3306 -j ACCEPT添加到/etc/sysconfig/iptables即可   --在iptables中添加允许规则(注意不是添加在最后) [root@mysql ~]# vim /etc/sysconfig/iptables 
# Firewall configuration written by system-config-firewall # Manual customization of this file is not recommended. *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT -A INPUT -p icmp -j ACCEPT -A INPUT -i lo -j ACCEPT -A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT -A INPUT -m state --state NEW -m tcp -p tcp --dport 3306 -j ACCEPT --表示允许3306端口通过防火墙 -A INPUT -j REJECT --reject-with icmp-host-prohibited -A FORWARD -j REJECT --reject-with icmp-host-prohibited COMMIT   --改完后重启iptables [root@mysql ~]# /etc/init.d/iptables restart iptables: Setting chains to policy ACCEPT: filter          [  OK  ] iptables: Flushing firewall rules:                         [  OK  ] iptables: Unloading modules:                               [  OK  ] iptables: Applying firewall rules:                         [  OK  ] 
这次再通过SQLyog客户端连接MySQL服务器，依然成功连接！可见，之前无法连接的问题就是因为3306被防火墙给阻挡了。

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