MySQL connection: Communications link failure

Question

I want to start my program on an external computer. The initial connection to the database works fine, but as soon as the first query is send to the database, I get this error:

Nov 18, 2013 10:55:24 AM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
WARN: SQL Error: 0, SQLState: 08S01
Nov 18, 2013 10:55:24 AM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
ERROR: 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.
org.hibernate.exception.JDBCConnectionException: Could not open connection
    at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:132)
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:110)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:221)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection(LogicalConnectionImpl.java:157)
    at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.doBegin(JdbcTransaction.java:67)
    at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.begin(AbstractTransactionImpl.java:160)
    at org.hibernate.internal.SessionImpl.beginTransaction(SessionImpl.java:1432)
    at de.util.HibernateUtil.getList(HibernateUtil.java:230)
    at de.commands.login.LoginCommand.executeServer(LoginCommand.java:35)
    at de.commands.login.LoginCommand.executeServer(LoginCommand.java:20)
    at de.commands.SessionManager.execute(SessionManager.java:142)
    at de.commands.SessionManager.execute(SessionManager.java:124)
    at de.commands.CommandExecutionThread.run(CommandExecutionThread.java:27)
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:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1121)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:357)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2482)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2519)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2304)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:834)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:416)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:346)
    at org.hibernate.service.jdbc.connections.internal.DriverManagerConnectionProviderImpl.getConnection(DriverManagerConnectionProviderImpl.java:204)
    at org.hibernate.internal.AbstractSessionImpl$NonContextualJdbcConnectionAccess.obtainConnection(AbstractSessionImpl.java:292)
    at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:214)
    ... 10 more
Caused by: java.net.ConnectException: Connection refused
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:391)
    at java.net.Socket.connect(Socket.java:579)
    at java.net.Socket.connect(Socket.java:528)
    at java.net.Socket.<init>(Socket.java:425)
    at java.net.Socket.<init>(Socket.java:241)
    at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:259)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:307)
    ... 25 more

Having looked through other threads, other people had problems with the timeout. My problems seems different since it says the last package received was 0ms ago. Also, working with phpmyadmin never caused any problems. Nevertheless, my timeout values are:

connect_timeout: 10
interactive_timeout: 28800
wait_timeout: 28800

Edit:

Here my hibernate config:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost/ws?autoReconnect=true&user=user&password=pw</property>
        [...]
    </session-factory>
</hibernate-configuration>

The method in which I access the database:

public static <T> List<T> getList(DetachedCriteria criteria)
{
    SessionFactory sf = HibernateUtil.getSessionFactory();
    Session session = null;
    List<T> l = new LinkedList<>();

    try
    {
        session = sf.openSession();
        session.beginTransaction();  // This is the line where the exception occurs
        List list = criteria.getExecutableCriteria(session).list();
        for (Object o : list)
        {
            l.add((T) o);
        }
        session.getTransaction().commit();
    } catch (HibernateException he)
    {
        he.printStackTrace();
    } finally
    {
        session.close();
    }

    return l;
}

post questions with some codes.At least can you post hibernate.cfg.xml file? — Ami, Nov 18 '13 at 10:12
Added my hibernate config and the code where I access the database. — user1406177, Nov 18 '13 at 10:39
check http://stackoverflow.com/a/10772407/2628911 and http://stackoverflow.com/a/2830222/2628911 — Sandhu Santhakumar, Nov 18 '13 at 12:43

score 0 · Answer 1 · edited Aug 01 '14 at 12:53

Yust make shure youre JDBC link is correct, il give an example:

It should look like this:

return conn = DriverManager.getConnection("jdbc:mysql://"+IP+"/"+DB, User, Pass);

Make youre own Database and use youre information on the JDBC link:

//DB: exampledb
//Database username: exampleusername
//Pass: examplepassword


return conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/exampledb","exampleusername", "examplepassword");

The ports are needed to connect to the MySQL. (you can choose 127.0.0.1:3306 or localhost:3306) They are both the same.

Hoped this helped you out.

MySQL connection: Communications link failure

1 Answers1