无法使用JDBC连接到MySQL - 连接超时 - Ubuntu 9.04

Question

我正在运行Ubuntu,并且最终尝试使用JDBC将Tomcat连接到我的MySQL数据库.

它以前工作过,但重新启动后,实例现在无法连接.

• Tomcat 6和MySQL 5.0.75都在同一台机器上
• 连接字符串:jdbc:mysql:/// localhost:3306
• 我可以使用mysql命令在命令行上连接MySQL
• my.cnf文件非常标准(可根据要求提供)具有绑定地址:127.0.0.1
• 尽管netstat说MySQL在监听,但我无法远程登陆MySQL端口
• 我有一个IpTables规则转发80 - > 8080并且没有我知道的防火墙.

我对此很陌生,我不确定还有什么可以测试.我不知道我是否应该在etc/interfaces中寻找,如果我做了什么寻找.它很奇怪,因为它曾经工作但重启后它已经失效所以我必须改变一些东西...... :).

我意识到超时表明服务器没有响应,我认为这是因为请求实际上没有通过.我通过apt-get和Tomcat手动安装了MySQL.

MySqld进程

root@88:/var/log/mysql#  ps -ef | grep mysqld
root     21753     1  0 May27 ?        00:00:00 /bin/sh /usr/bin/mysqld_safe
mysql    21792 21753  0 May27 ?        00:00:00 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql --pid-file=/var/run/mysqld/mysqld.pid --skip-external-locking --port=3306 --socket=/var/run/mysqld/mysqld.sock
root     21793 21753  0 May27 ?        00:00:00 logger -p daemon.err -t mysqld_safe -i -t mysqld
root     21888 13676  0 11:23 pts/1    00:00:00 grep mysqld

用netstat

root@88:/var/log/mysql# netstat -lnp | grep mysql
tcp        0      0 0.0.0.0:3306            0.0.0.0:*               LISTEN      21792/mysqld
unix  2      [ ACC ]     STREAM     LISTENING     1926205077 21792/mysqld        /var/run/mysqld/mysqld.sock

玩具连接类

root@88:~# cat TestConnect/TestConnection.java

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class TestConnection {

  public static void main(String args[]) throws Exception {
    Connection con = null;

    try {
      Class.forName("com.mysql.jdbc.Driver").newInstance();
      System.out.println("Got driver");
      con = DriverManager.getConnection(
                "jdbc:mysql:///localhost:3306",
                "uname", "pass");
      System.out.println("Got connection");

      if(!con.isClosed())
        System.out.println("Successfully connected to " +
          "MySQL server using TCP/IP...");

    } finally {
        if(con != null)
          con.close();
    }
  }
}

玩具连接类输出

注意:这与我从Tomcat获得的错误相同.

root@88:~/TestConnect# java -cp mysql-connector-java-5.1.12-bin.jar:. TestConnection
Got driver
                Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 1 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:39)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
        at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1122)            
        at TestConnection.main(TestConnection.java:14)
Caused by: 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.
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
        at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1122)
        at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:344)
        at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2181)
        ... 12 more
Caused by: java.net.ConnectException: Connection timed out
        at java.net.PlainSocketImpl.socketConnect(Native Method)
        ... 13 more

Telnet输出

root@88:~/TestConnect# telnet localhost 3306
Trying 127.0.0.1...
telnet: Unable to connect to remote host: Connection timed out

Answer 1

Netstat 显示 MySQL 确实正在监听所有本地地址的端口 3306。由于 telnet 无法连接到 127.0.0.1，因此存在防火墙阻止您 - 尝试运行sudo ufw default allow以有效禁用它，或者sudo ufw allow 3306查看它是否进行任何更改。