java - MySQL : Communication Link failure error and telnet localhost 3306 : Connection close

Question

我正在尝试使用 Java 连接 MYSQL 数据库，而我的 SQL 数据库位于本地主机上。 我面临着一些关于通信链路故障的问题。

public testfile() throws ClassNotFoundException, SQLException{

        Connection connection = null;
        try{
        Class.forName("com.mysql.jdbc.Driver").newInstance(); 
        connection = DriverManager.getConnection("jdbc:mysql://localhost/rts?user=root&password=password");
        System.out.println("Connected");
        }
        catch(Exception ex)
        {
            ex.printStackTrace();
        }
        finally
        {
            if(connection != null)
                connection.close();
        }
}

堆栈跟踪:

com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: 

** BEGIN NESTED EXCEPTION ** 

java.net.ConnectException
MESSAGE: Connection refused

STACKTRACE:

java.net.ConnectException: Connection refused
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:327)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:193)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:180)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:384)
    at java.net.Socket.connect(Socket.java:546)
    at java.net.Socket.connect(Socket.java:495)
    at java.net.Socket.<init>(Socket.java:392)
    at java.net.Socket.<init>(Socket.java:235)
    at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:271)
    at com.mysql.jdbc.Connection.createNewIO(Connection.java:2771)
    at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
    at java.sql.DriverManager.getConnection(DriverManager.java:620)
    at java.sql.DriverManager.getConnection(DriverManager.java:222)
    at test.testfile.<init>(testfile.java:18)
    at test.mainfile.main(mainfile.java:9)


** END NESTED EXCEPTION **



Last packet sent to the server was 1 ms ago.
    at com.mysql.jdbc.Connection.createNewIO(Connection.java:2847)
    at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
    at java.sql.DriverManager.getConnection(DriverManager.java:620)
    at java.sql.DriverManager.getConnection(DriverManager.java:222)
    at test.testfile.<init>(testfile.java:18)
    at test.mainfile.main(mainfile.java:9)

远程登录输出:

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

包/软件信息:

• 面向 Web 开发人员的 Eclipse Java EE IDE。
• 版本:Helios Service Release 1。
• JDK6
• 连接器/J 版本 5.0.8
• Ubuntu:Ubuntu 10.04 LTS——清醒山猫

我已经尝试了一些东西，但它不起作用:

• 我在 my.cnf 中更改了端口但没有效果，我更改为 3312 同样的错误重复出现，telnet显示如下:

  shreya@shreya-laptop:~$ telnet localhost 3306
  Trying 127.0.0.1...
  telnet: Unable to connect to remote host: Connection refused
  shreya@shreya-laptop:~$ telnet localhost 3312
  Trying 127.0.0.1...
  Connected to localhost.
  Escape character is '^]'.
  Connection closed by foreign host.
  

  nmap 输出:

  shreya@shreya-laptop:~$ nmap localhost -p 3306
  
  Starting Nmap 5.00 ( [url]http://nmap.org[/url] ) at 2011-03-31 09:45 IST
  Interesting ports on localhost (127.0.0.1):
  PORT     STATE  SERVICE
  3306/tcp closed mysql
  
  Nmap done: 1 IP address (1 host up) scanned in 0.11 seconds
  shreya@shreya-laptop:~$ nmap localhost -p 3312
  
  Starting Nmap 5.00 ( [url]http://nmap.org[/url] ) at 2011-03-31 09:45 IST
  Interesting ports on localhost (127.0.0.1):
  PORT     STATE SERVICE
  3312/tcp open  unknown
  
  Nmap done: 1 IP address (1 host up) scanned in 0.06 seconds
  

• 我尝试将条目放入 hosts.allow 但没有效果

• 我试过重新安装 mysql。通过 mysql 提示符和 c 程序插入数据可以完美运行，但不能通过 java 代码插入。

• 我尝试在 ip 表中添加规则仍然没有帮助

• 我尝试了不同的 url 字符串组合。我也试过不同版本的 eclipse 和 Connector/J jar 文件(最新的 5.1.15)

Answer 1

首先使用程序中使用的相同凭据尝试使用 MYSQL 命令行客户端 连接到 MySQL。