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How to connect to a remote MySQL server via JDBC with Android Applicaton

I figured out how to connect to a remote MySQL server in a Java application. I know that very well. I provided my code and the steps that I took to do the same, but from an Android application.

Question What is wrong with my code that it does not connect? I used a similar process in Java and it works great.

1) I added the external mysql-connector.jar JAR file in the project properties (I used 5.1, I believe). This works great because I use it in my Java application and connect to it.

2) Below is the code for connecting and querying the database. I left the request information and server information replaced with <>. Obviously: P

3) When I launch the application on my phone, I get the following message:

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communication communication error.

4) I run wirehark on an Ubuntu server and just see SSTP entries when it listens on the mysql port.

package com.example.test_android; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.Statement; import android.app.Activity; import android.os.Bundle; import android.widget.TextView; public class MainActivity extends Activity { private static final String url = "jdbc:mysql://<server ip>:<sql port#>/<database name>"; private static final String user = "<username>"; private static final String pass = "<password>"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); testDB(); }//end oncreate method public void testDB() { TextView tv = (TextView)this.findViewById(R.id.text_view); try { Class.forName("com.mysql.jdbc.Driver"); Connection con = DriverManager.getConnection(url, user, pass); /* System.out.println("Database connection success"); */ String result = "Database connection success\n"; Statement st = con.createStatement(); ResultSet rs = st.executeQuery("SELECT * FROM <table in database>"); ResultSetMetaData rsmd = rs.getMetaData(); while(rs.next()) { result += rsmd.getColumnName(1) + ": " + rs.getInt(1) + "\n"; result += rsmd.getColumnName(2) + ": " + rs.getString(2) + "\n"; result += rsmd.getColumnName(3) + ": " + rs.getString(3) + "\n"; } tv.setText(result); } catch(Exception e) { e.printStackTrace(); tv.setText(e.toString()); } } }//end class

5) Stack Trace:

 03-20 11:50:46.381: W/SurfaceFlinger(334): id=54501 Removed idx=5 Map Size=4 03-20 11:50:46.381: D/memalloc(334): ion: Freeing buffer base:0x42fb0000 size:1228800 fd:50 03-20 11:50:46.381: D/memalloc(334): ion: Freeing buffer base:0x43107000 size:1228800 fd:11 03-20 11:50:46.381: W/SurfaceFlinger(334): id=54501 Removed idx=-2 Map Size=4 03-20 11:50:46.381: D/memalloc(334): ion: Freeing buffer base:0x43c2d000 size:1228800 fd:53 03-20 11:50:46.381: D/KeyguardViewMediator(648): setHidden false 03-20 11:50:47.302: E/MP-Decision(1366): DOWN Ld:51 Ns:1.100000 Ts:190 rq:1.000000 seq:196.000000 03-20 11:50:47.492: D/STATUSBAR-NetworkController(805): onReceive() - RSSI_CHANGED_ACTION, WIFI_STATE, NETWORK_STATE 03-20 11:50:48.143: E/SMD(330): DCD ON 03-20 11:50:48.603: V/WindowOrientationListener(648): nearestRotation : 0 Angle: 348 tilt: 45 03-20 11:50:50.535: D/STATUSBAR-NetworkController(805): onReceive() - RSSI_CHANGED_ACTION, WIFI_STATE, NETWORK_STATE 03-20 11:50:50.555: E/MP-Decision(1366): UP Ld:50 Nw:1.990000 Tw:140 rq:2.700000 seq:147.000000 03-20 11:50:50.946: W/dalvikvm(23747): VFY: unable to find class referenced in signature (Ljavax/naming/Reference;) 03-20 11:50:50.946: I/dalvikvm(23747): Could not find method javax.naming.Reference.get, referenced from method com.mysql.jdbc.ConnectionPropertiesImpl$ConnectionProperty.initializeFrom 03-20 11:50:50.946: W/dalvikvm(23747): VFY: unable to resolve virtual method 11306: Ljavax/naming/Reference;.get (Ljava/lang/String;)Ljavax/naming/RefAddr; 03-20 11:50:50.946: D/dalvikvm(23747): VFY: replacing opcode 0x6e at 0x0004 03-20 11:50:50.946: W/dalvikvm(23747): VFY: unable to find class referenced in signature (Ljavax/naming/Reference;) 03-20 11:50:50.946: E/dalvikvm(23747): Could not find class 'javax.naming.StringRefAddr', referenced from method com.mysql.jdbc.ConnectionPropertiesImpl$ConnectionProperty.storeTo 03-20 11:50:50.946: W/dalvikvm(23747): VFY: unable to resolve new-instance 944 (Ljavax/naming/StringRefAddr;) in Lcom/mysql/jdbc/ConnectionPropertiesImpl$ConnectionProperty; 03-20 11:50:50.946: D/dalvikvm(23747): VFY: replacing opcode 0x22 at 0x0006 03-20 11:50:50.956: D/dalvikvm(23747): DexOpt: unable to opt direct call 0x2c2c at 0x14 in Lcom/mysql/jdbc/ConnectionPropertiesImpl$ConnectionProperty;.storeTo 03-20 11:50:51.146: E/SMD(330): DCD ON 03-20 11:50:51.476: I/dalvikvm(23747): Could not find method java.lang.management.ManagementFactory.getThreadMXBean, referenced from method com.mysql.jdbc.MysqlIO.appendDeadlockStatusInformation 03-20 11:50:51.476: W/dalvikvm(23747): VFY: unable to resolve static method 10657: Ljava/lang/management/ManagementFactory;.getThreadMXBean ()Ljava/lang/management/ThreadMXBean; 03-20 11:50:51.476: D/dalvikvm(23747): VFY: replacing opcode 0x71 at 0x0079 03-20 11:50:51.576: W/System.err(23747): com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure 03-20 11:50:51.576: W/System.err(23747): The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server. 03-20 11:50:51.576: W/System.err(23747): at java.lang.reflect.Constructor.constructNative(Native Method) 03-20 11:50:51.576: W/System.err(23747): at java.lang.reflect.Constructor.newInstance(Constructor.java:417) 03-20 11:50:51.576: W/System.err(23747): at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) 03-20 11:50:51.586: W/System.err(23747): at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116) 03-20 11:50:51.586: W/System.err(23747): at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:344) 03-20 11:50:51.586: W/System.err(23747): at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2332) 03-20 11:50:51.586: W/System.err(23747): at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2369) 03-20 11:50:51.586: W/System.err(23747): at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2153) 03-20 11:50:51.586: W/System.err(23747): at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:792) 03-20 11:50:51.596: W/System.err(23747): at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47) 03-20 11:50:51.596: W/System.err(23747): at java.lang.reflect.Constructor.constructNative(Native Method) 03-20 11:50:51.596: W/System.err(23747): at java.lang.reflect.Constructor.newInstance(Constructor.java:417) 03-20 11:50:51.596: W/System.err(23747): at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) 03-20 11:50:51.596: W/System.err(23747): at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381) 03-20 11:50:51.596: W/System.err(23747): at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305) 03-20 11:50:51.606: W/System.err(23747): at java.sql.DriverManager.getConnection(DriverManager.java:175) 03-20 11:50:51.606: W/System.err(23747): at java.sql.DriverManager.getConnection(DriverManager.java:209) 03-20 11:50:51.606: W/System.err(23747): at com.example.test_android.MainActivity.testDB(MainActivity.java:34) 03-20 11:50:51.606: W/System.err(23747): at com.example.test_android.MainActivity.onCreate(MainActivity.java:24) 03-20 11:50:51.606: W/System.err(23747): at android.app.Activity.performCreate(Activity.java:4470) 03-20 11:50:51.616: W/System.err(23747): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1053) 03-20 11:50:51.616: W/System.err(23747): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1934) 03-20 11:50:51.616: W/System.err(23747): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1995) 03-20 11:50:51.616: W/System.err(23747): at android.app.ActivityThread.access$600(ActivityThread.java:128) 03-20 11:50:51.616: W/System.err(23747): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1161) 03-20 11:50:51.616: W/System.err(23747): at android.os.Handler.dispatchMessage(Handler.java:99) 03-20 11:50:51.626: W/System.err(23747): at android.os.Looper.loop(Looper.java:137) 03-20 11:50:51.626: W/System.err(23747): at android.app.ActivityThread.main(ActivityThread.java:4517) 03-20 11:50:51.626: W/System.err(23747): at java.lang.reflect.Method.invokeNative(Native Method) 03-20 11:50:51.626: W/System.err(23747): at java.lang.reflect.Method.invoke(Method.java:511) 03-20 11:50:51.626: W/System.err(23747): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:980) 03-20 11:50:51.626: W/System.err(23747): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747) 03-20 11:50:51.636: W/System.err(23747): at dalvik.system.NativeStart.main(Native Method) 03-20 11:50:51.636: W/System.err(23747): Caused by: java.net.SocketException: android.os.NetworkOnMainThreadException 03-20 11:50:51.636: W/System.err(23747): at com.mysql.jdbc.StandardSocketFactory.unwrapExceptionToProperClassAndThrowIt(StandardSocketFactory.java:408) 03-20 11:50:51.636: W/System.err(23747): at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:269) 03-20 11:50:51.646: W/System.err(23747): at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:294) 03-20 11:50:51.646: W/System.err(23747): ... 28 more 03-20 11:50:51.786: W/SurfaceFlinger(334): id=54502(1) createSurface 0x1b75144 (1x1),2 flag=400 03-20 11:50:51.786: D/KeyguardViewMediator(648): setHidden false 03-20 11:50:51.786: D/STATUSBAR-StatusBarManagerService(648): setSystemUiVisibility(0x0) 03-20 11:50:51.786: D/STATUSBAR-StatusBarManagerService(648): manageDisableList what=0x0 pkg=WindowManager.LayoutParams 03-20 11:50:51.867: D/CLIPBOARD(1073): Hide Clipboard dialog at Starting input: finished by someone else... ! 03-20 11:50:51.867: I/ClipboardServiceEx(648): mCBPickerDialog enter case. MSG_DISMISS_DIALOG 03-20 11:50:51.867: I/ClipboardServiceEx(648): Send intent for dismiss clipboard dialog inside hideCurrentInputLocked() !
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1 answer

There are two reasons why he does not work here.

jdbc cannot hit the url you tell it, the url must be public, which means your server, that is: SAY xyzw: port

so you need a network guy to free this port on the ip server and make it public

Attention

Opening this publicly will make your database a threat, as anyone who knows can write it.

WORD OF CONSULTATIONS NEVER allow your application to directly communicate with the database, allow server technologies such as jsp, servlets, asp, python, etc. to receive your request and do it for you.

I hope this helps.

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