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I have developed small app after watching a tutorial on how to connect MYSQL database with android apps. I have been testing this app on android emulator, but so far I haven't figured out whats going wrong.

I have searched the whole stackoverflow over this issue, but no success so far.

Stackoverflow contains solutions like 'using 10.0.2.2:8080', 'using your own ip address', 'switching off firewall settings', 'changing apache server (configuration) settings' and many more, but none of them have worked for me.

Here's my code:

BackgroundWorker.java

package apps.harry.mysqldemo;

import android.app.AlertDialog;
import android.content.Context;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;

/**
 * Created by harry on 18/11/2017.
 */
public class BackgroundWorker extends AsyncTask<String,Void,String> {
    Context context;
    AlertDialog alertDialog;
    Log log;
    int a=0;
    BackgroundWorker (Context ctx) {
        context = ctx;
    }
    @Override
    protected String doInBackground(String... params)
    {
        String type = params[0];
        String login_url = "http://10.0.2.2:8081/login.php";
        if(type.equals("login")) {
            try {
                a=1;//for debugging purposes

                String user_name = params[1];
                String password = params[2];

                URL url = new URL(login_url);

                HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();

                httpURLConnection.setRequestMethod("POST");

                httpURLConnection.setDoOutput(true);
                httpURLConnection.setDoInput(true);

                OutputStream outputStream = httpURLConnection.getOutputStream();// this line seems to be some problem as during debugging it never crossed this line and hence you will see in logcat "erro is beacuse null 1", not "2"
                a=2;//for debugging purposes
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
                String post_data = URLEncoder.encode("user_name","UTF-8")+"="+URLEncoder.encode(user_name,"UTF-8")+"&"
                        +URLEncoder.encode("password","UTF-8")+"="+URLEncoder.encode(password,"UTF-8");
                bufferedWriter.write(post_data);
                bufferedWriter.flush();
                bufferedWriter.close();
                outputStream.close();
                InputStream inputStream = httpURLConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream,"iso-8859-1"));
                String result="";
                String line="";
                while((line = bufferedReader.readLine())!= null)
                {
                    result += line;
                }
                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();

                return result;
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        //a=3;
        return null;
    }

    @Override
    protected void onPreExecute() {
        alertDialog = new AlertDialog.Builder(context).create();
        alertDialog.setTitle("Login Status");
        log.e("onpostexecute","bg");
    }

    @Override
    protected void onPostExecute(String result) {
        alertDialog.setMessage(result);
        alertDialog.show();
    log.e("onpostexecute","erro is beacuse "+result+" "+a);

    }

    @Override
    protected void onProgressUpdate(Void... values) {
        super.onProgressUpdate(values);
    }
}



MainActivity.java 

package apps.harry.mysqldemo;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;

public class MainActivity extends AppCompatActivity
{

    EditText uname_et,pass_et;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        uname_et=findViewById(R.id.uname_et);
        pass_et=findViewById(R.id.pass_et);

    }

    public void onLogin(View view)
    {
        String user_name=uname_et.getText().toString();
        String pass_word=pass_et.getText().toString();
        String type="login";

        BackgroundWorker backgroundWorker=new BackgroundWorker(this);
        backgroundWorker.execute(type,user_name,pass_word);
    }
}



During the debugging process i found out these lines in logcat, have a look: 

D/NetworkSecurityConfig: No Network Security Config specified, using platform default
11-20 17:55:10.604 6165-6189/apps.harry.mysqldemo W/System.err: java.net.ConnectException: Failed to connect to /10.0.2.2:8081
11-20 17:55:10.604 6165-6189/apps.harry.mysqldemo W/System.err:     at com.android.okhttp.internal.io.RealConnection.connectSocket(RealConnection.java:143)
11-20 17:55:10.604 6165-6189/apps.harry.mysqldemo W/System.err:     at com.android.okhttp.internal.io.RealConnection.connect(RealConnection.java:112)
11-20 17:55:10.604 6165-6189/apps.harry.mysqldemo W/System.err:     at com.android.okhttp.internal.http.StreamAllocation.findConnection(StreamAllocation.java:184)
11-20 17:55:10.604 6165-6189/apps.harry.mysqldemo W/System.err:     at com.android.okhttp.internal.http.StreamAllocation.findHealthyConnection(StreamAllocation.java:126)
11-20 17:55:10.604 6165-6189/apps.harry.mysqldemo W/System.err:     at com.android.okhttp.internal.http.StreamAllocation.newStream(StreamAllocation.java:95)
11-20 17:55:10.604 6165-6189/apps.harry.mysqldemo W/System.err:     at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:281)
11-20 17:55:10.604 6165-6189/apps.harry.mysqldemo W/System.err:     at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:224)
11-20 17:55:10.604 6165-6189/apps.harry.mysqldemo W/System.err:     at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:461)
11-20 17:55:10.604 6165-6189/apps.harry.mysqldemo W/System.err:     at com.android.okhttp.internal.huc.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:127)
11-20 17:55:10.604 6165-6189/apps.harry.mysqldemo W/System.err:     at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getOutputStream(HttpURLConnectionImpl.java:258)
11-20 17:55:10.605 6165-6189/apps.harry.mysqldemo W/System.err:     at apps.harry.mysqldemo.BackgroundWorker.doInBackground(BackgroundWorker.java:54)
11-20 17:55:10.605 6165-6189/apps.harry.mysqldemo W/System.err:     at apps.harry.mysqldemo.BackgroundWorker.doInBackground(BackgroundWorker.java:25)
11-20 17:55:10.605 6165-6189/apps.harry.mysqldemo W/System.err:     at android.os.AsyncTask$2.call(AsyncTask.java:333)
11-20 17:55:10.605 6165-6189/apps.harry.mysqldemo W/System.err:     at java.util.concurrent.FutureTask.run(FutureTask.java:266)
11-20 17:55:10.606 6165-6189/apps.harry.mysqldemo W/System.err:     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
11-20 17:55:10.606 6165-6189/apps.harry.mysqldemo W/System.err:     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
11-20 17:55:10.606 6165-6189/apps.harry.mysqldemo W/System.err:     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
11-20 17:55:10.606 6165-6189/apps.harry.mysqldemo W/System.err:     at java.lang.Thread.run(Thread.java:764)
11-20 17:55:10.747 6165-6165/apps.harry.mysqldemo E/onpostexecute: erro is beacuse null 1



and, not only Failed to connect to /10.0.2.2:8081, it also failed to connect Failed to connect to /localhost:8081 and Failed to connect to /192.168.0.5:8081

I am really out of solutions. I don't know what to do.
Please help me out.

Steve
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1 Answers1

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the error indicates that you're not using a Network Security Configuration as specified in this answer and to configure add Security Configuration File and include an entry in the manifest of your app to point to this file as specified in https://developer.android.com/training/articles/security-config.html#manifest it also show how to configure certificate authority (CAs) for debugging

baba
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