Remote Database

Question

I tried creating an app in java that works with a remote database. The apps works fine on a local database. I have included the the port number as well. I am scared that it may be the IP address I am using.

I thought to myself there may be hundreds if not thousands of pc's around the world with the same IP as mine... and how does the Internet see which one I am, or stay secure about it. I am sure you don't give the remote access the IP of you computer of you home network, but I may be wrong... I honestly don't know.

This is my function.

public void db() {
    try {
        Class.forName("com.mysql.jdbc.Driver");
        Connection myCon = DriverManager.getConnection("jdbc:mysql://IPOfWebSite:3306/DatabaseName", "UserName", "Password"); 
        System.out.println("Connected");
        myCon.close();
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

On the Remote DB I have added my public IP address, but still received this error

"C:\Program Files\Java\jdk1.8.0_25\bin\java" -Didea.launcher.port=7532 "-Didea.launcher.bin.path=C:\Program Files (x86)\JetBrains\IntelliJ IDEA Community Edition 14.1.3\bin" -Dfile.encoding=windows-1252 -classpath "C:\Program Files\Java\jdk1.8.0_25\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\rt.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_25\jre\lib\ext\zipfs.jar;H:\Java Dev\Simple_java_DB\out\production\Simple_java_DB;H:\Java Dev\Simple_java_DB\mysql-connector-java-5.1.35\mysql-connector-java-5.1.35\mysql-connector-java-5.1.35-bin.jar;C:\Program Files (x86)\JetBrains\IntelliJ IDEA Community Edition 14.1.3\lib\idea_rt.jar" com.intellij.rt.execution.application.AppMain Main
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:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:408)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:389)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1038)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:338)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2237)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2270)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2069)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:794)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:44)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:408)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:389)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:399)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:325)
    at java.sql.DriverManager.getConnection(DriverManager.java:664)
    at java.sql.DriverManager.getConnection(DriverManager.java:247)
    at Main.db(Main.java:24)
    at Main.main(Main.java:15)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:140)
Caused by: java.net.ConnectException: Connection refused: connect
    at java.net.DualStackPlainSocketImpl.connect0(Native Method)
    at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:345)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:213)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:297)
    ... 21 more

Any help will be great. By the way I did check my firewall... it should allow the port to receive and sent.

Answer 1

1) Make sure you're adding your external IP, not your internal network IP (192.168.x.x).

Go to: https://www.whatismyip.com/ and use that IP for whitelisting your IP in the remote DB's firewall and/or access restrictions.

2) Make sure your mysql user is set up with the correct host, either 'user'@'your-external-ip' or 'user'@'%' (to allow that user to connect from any IP).

3) Make sure your my.conf is set up to allow remote connections. Make sure you're not binding to 127.0.0.1, instead temporarily do:

bind-address = 0.0.0.0;

You should set this to your server's actual IP, but 0.0.0.0 will work for any IP and should just be used temporarily to verify that this is your problem. Long term it could pose a security risk to leave it as 0.0.0.0.

Also make sure that you're not skipping networking. Make sure this line is commented out (with a # in front of it):

# skip-networking

Answer 2

MySQL does by default only listen to the local interface (loopback). So you can only reach it from the local machine.

To change this, adapt the MySQL conf:

[mysqld] 
bind-address=YOUR-SERVER-IP

Also, make sure the skip-networking configuration is commented out or not present.

More details here.