Question

Most recent problem is “Third Error” listed below.

I am working on an application in java that needs to connect to a database. Below is the code that i am using to attempt to connect to the database. The port is 3306 and i have the database set up on a machine here at my house on the network. For the ip address i am just using my external ip address to the world. The username and password were replaced for my protection. In my /etc/mysql/my.cnf, “bind_address” is commented out.

I have tried several things and can not seem to get this to work. This is my first time using JDBC… thanks for any help! Let me know if you need more information.

        Class.forName("com.mysql.jdbc.Driver").newInstance();
        System.out.println("before connection");
        connect = DriverManager.getConnection("jdbc:mysql://ip-address/mjla_db", "username", "password");
        System.out.println("connection established");

Here is the error that i keep getting:

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(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    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:2332)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2369)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2153)
    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(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    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(Unknown Source)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at school.cs321.mjla.MJLA.main(MJLA.java:30)
Caused by: java.net.ConnectException: Connection refused: connect
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.PlainSocketImpl.doConnect(Unknown Source)
    at java.net.PlainSocketImpl.connectToAddress(Unknown Source)
    at java.net.PlainSocketImpl.connect(Unknown Source)
    at java.net.SocksSocketImpl.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at java.net.Socket.<init>(Unknown Source)
    at java.net.Socket.<init>(Unknown Source)
    at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:257)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:294)
    ... 15 more

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Second Error
After changing ip address to the internal ip address of the server.

java.sql.SQLException: null,  message from server: "Host '192.168.1.102' is not allowed to connect to this MySQL server"
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1073)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982)
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1128)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2336)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2369)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2153)
    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(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    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(Unknown Source)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at school.cs321.mjla.MJLA.main(MJLA.java:30)

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Third error
When trying to access the database with the external ip address on an external network, i get the same error that i had initially.

I am using the “%” wild card for the Host of the username i am using for the application to authenticate to the database.

Answer 1

@Dave Newton: I was making the assumption that my firewall still had the port open for mysql, because i just got through working on a project where i did the same thing. However, i must have closed it a couple months ago. I checked a few minutes ago and it was disabled. So, i enabled and it is working fine now. Not sure why it had been closed…