Error Cannot connect to database server Communications link failure

0 votes

I'm trying to connect to the local MySQL server but I keep getting an error.

Here is the code.

public class Connect {

    public static void main(String[] args) {
        Connection conn = null;

        try {
            String userName = "myUsername";
            String password = "myPassword";

            String url = "jdbc:mysql://localhost:3306/myDatabaseName";
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            conn = DriverManager.getConnection(url, userName, password);
            System.out.println("Database connection established");
        } catch (Exception e) {
            System.err.println("Cannot connect to database server");
            System.err.println(e.getMessage());
            e.printStackTrace();
        } finally {
            if (conn != null) {
                try {
                    conn.close();
                    System.out.println("Database Connection Terminated");
                } catch (Exception e) {}
            }
        }
    }
}

and the errors :

Cannot connect to database server
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.
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:411)
        at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)
        at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:344)
        at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2333)
        at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2370)
        at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2154)
        at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:792)
        at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
        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:411)
        at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381)
        at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
        at java.sql.DriverManager.getConnection(DriverManager.java:582)
        at java.sql.DriverManager.getConnection(DriverManager.java:185)
        at Connect.main(Connect.java:16)
    Caused by: java.net.ConnectException: Connection refused
        at java.net.PlainSocketImpl.socketConnect(Native Method)
        at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:351)
        at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:213)
        at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:200)
        at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
        at java.net.Socket.connect(Socket.java:529)
        at java.net.Socket.connect(Socket.java:478)
        at java.net.Socket.<init>(Socket.java:375)
        at java.net.Socket.<init>(Socket.java:218)
        at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:257)
        at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:294)
        ... 15 more

I've set the classpath, made sure my.cnf had the skip network option commented out.

Aug 19, 2020 in PHP by kartik
• 37,510 points
515 views

1 answer to this question.

0 votes

Hello @kartik,

Setting the bind-address to the server's network IP instead of the localhost default, and setting privileges on my user worked for me.

my.cnf:

bind-address = 192.168.123.456

MySql Console:

GRANT ALL PRIVILEGES ON dbname.* to username@'%' IDENTIFIED BY 'password';

Hope it helps!!
Thank you!!

answered Aug 19, 2020 by Niroj
• 82,800 points

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