我正在运行 Ubuntu,并最终尝试使用 JDBC 将 Tomcat 连接到我的 MySQL 数据库。
以前也曾奏效但重新启动后,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
mysql
我可以使用以下命令在命令行上连接到 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 显示 MySQL 正在监听,但我无法 Telnet 到 MySQL 端口
- 我有一个 IpTables 规则来转发 80 -> 8080,并且我知道没有防火墙。
我对此还很陌生,我不确定还要测试什么。我不知道我是否应该查看 etc/interfaces,以及我是否做了要查找的内容。这很奇怪,因为它以前可以工作,但重启后就关闭了,所以我一定是做了一些更改……:)。
我意识到超时表示服务器没有响应,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
网络状态
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:这是我从 Tomcat 得到的相同错误。
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
iptables 目录
注意:我确实为 NAT 设置了规则,但我将其删除后问题仍然存在。
root@88:~# iptables -nL
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
root@88:~# iptables -t nat -nL
Chain PREROUTING (policy ACCEPT)
target prot opt source destination
Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
用于设置 iptables 的命令
iptables -t nat -I PREROUTING --src 0/0 --dst 88.198.31.14 -p tcp --dport 80 -j REDIRECT --to-ports 8080
从那时起,我删除了为 NAT 设置的规则,因此除非该命令有副作用,否则它是无关的。
更新-我无法 ping 本地主机
知识产权
root@88:~/TestConnect# ip a
1: lo: <LOOPBACK> mtu 16436 qdisc noop state DOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
3: venet0: <BROADCAST,POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
link/void
inet 127.0.0.1/32 scope host venet0
inet 88.198.31.14/32 scope global venet0:0
知识产权
root@88:~/TestConnect# ip r
192.0.2.1 dev venet0 scope link
default via 192.0.2.1 dev venet0
ip 规则
root@88:~/TestConnect# ip rule
0: from all lookup local
32766: from all lookup main
32767: from all lookup default
ping -c 1 本地主机
root@88:~/TestConnect# ping -c 1 localhost
PING localhost.localdomain (127.0.0.1) 56(84) bytes of data.
--- localhost.localdomain ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms
猫/等/主机
root@88:~/TestConnect# cat /etc/hosts
127.0.0.1 localhost.localdomain localhost
# Auto-generated hostname. Please do not remove this comment.
88.198.31.14 88.198.31.14 88 88
是否配置
root@88:/var/log/mysql# ifconfig
venet0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:127.0.0.1 P-t-P:127.0.0.1 Bcast:0.0.0.0 Mask:255.255.255.255
UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1
RX packets:144432 errors:0 dropped:0 overruns:0 frame:0
TX packets:153825 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:37896766 (37.8 MB) TX bytes:28722595 (28.7 MB)
venet0:0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:88.198.31.14 P-t-P:88.198.31.14 Bcast:0.0.0.0 Mask:255.255.255.255
UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1
感谢 pQd,我认为我们已经缩小了错误范围,我需要去了解这一切意味着什么以及为什么 localhost 无法 ping 通。
答案1
您是否绝对确定没有 iptables 规则阻止 tcp/3306 流量?尝试以下临时解决方法:
iptables -I INPUT -p tcp --dport 3306 -i lo -j ACCEPT
iptables -A OUTPUT -p tcp --sport 3306 -o lo -j ACCEPT
或者也许您的 NAT 规则比您预期的要多一点?
好的 - 您的环回不仅已关闭,而且没有绑定 127.0.0.1。添加到 /etc/network/interfaces:
auto lo
iface lo inet loopback
还有..你到底为什么将它绑定到 vnet0?从那里将其删除。
快速一次性 cmd 行修复:
ip a d 127.0.0.1/32 dev venet0
ip a a 127.0.0.1/32 dev lo
ip link set dev lo up