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

Im trying to connect MYSQL db using Java where my SQL db is on localhost. Im facing some issues regarding communication link failure.

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();
        }
}

Stack trace :

com.m开发者_C百科ysql.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)

Telnet output :

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

Package/Software Info :

• Eclipse Java EE IDE for Web Developers.
• Version: Helios Service Release 1.
• JDK6
• Connector/J version 5.0.8
• Ubuntu : Ubuntu 10.04 LTS- the Lucid Lynx

I have tried few things but it doesn't work:

• I changed port in my.cnf but no effect, I changed to 3312 same err repeats and telnet shows as follows :

  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 output :

  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
  

• I tried putting entry in hosts.allow but no effect

• I have tried reinstalling mysql. Insertion of data through mysql prompt and c program works perfectly but not through java code.

• I tried adding rules in ip tables still it doesnt help

• I have tried different combinations of url string. I have also tried different versions of eclipse and Connector/J jar file(latest 5.1.15)

---

First try to connect to MySQL using MYSQL Command Line Client using same credentials used in the program.

---

java.net.ConnectException: Connection refused

There is simply nothing which listens/accepts connections on the given host/port. Verify the following:

• Verify in my.cnf if port number is indeed 3306.
• Verify if the DB is started (use MySQL DB admin tool).
• Verify if DB accepts TCP/IP connections, mysqld shouldn't have --skip-networking option.
• Verify if the DB hasn't run out of connections, if necessary restart it and fix all existing Java code accordingly that it properly closes the connection in finally block.
• Verify if there isn't a firewall/proxy in between which blocks connections on the given port.

---

You need to grant permission to the user connecting over port 3306... This guy has a good explanation: link