Develop Reference

Socket For Android Emulator Works but Not For Real Device

I have java code that sends strings via ip to a python script. The code works perfectly with the emulator but when I successfully install the app via usb to my phone it does not work. Here is the code:
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
public class MainActivity extends AppCompatActivity {
public String message;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final Button btn_python = findViewById(R.id.python);
final Button btn_movie = findViewById(R.id.movie);
final Button btn_hw = findViewById(R.id.homework);
btn_python.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view1) {
send py = new send();
message = "python";
Log.i("Button", "Button works");
System.out.println("whatever");
py.execute();
}
});
btn_movie.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view2) {
send mov = new send();
message = "movie";
mov.execute();
}
});
btn_hw.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view2) {
send hw = new send();
message = "homework";
hw.execute();
}
});
}
class send extends AsyncTask<Void,Void,Void>{
Socket s;
PrintWriter pw;
#Override
protected Void doInBackground(Void...params) {
System.out.println("whatevernumbertwo");
try {
System.out.println("whatevernumberthree");
s = new Socket("ip address", 7800);
Log.i("Socket", "connects to socket");
pw = new PrintWriter(s.getOutputStream());
Log.i("output stream", "Output stream works");
pw.write(message);
Log.i("write", "Write works");
pw.flush();
Log.i("flush", "Flush works");
pw.close();
s.close();
} catch (UnknownHostException e) {
System.out.println("Fail");
e.printStackTrace();
} catch (IOException e) {
System.out.println("Fail");
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}
}
As I mentioned this works on the emulator but not on the actual device. The proper permissions have also been given. What am I doing wrong? Thanks in advance.

After much digging around, it turned out to be the server's firewall all along. That explains why (apparently) no exception was thrown, and why the code didn't seem to execute; it was executing, it was just getting stuck inside Socket() (during the connect).
Surely Socket() is, in fact, throwing an IOException; it probably just takes a while.
The code works on the emulator because, as it is operating on the same machine, it is behind the firewall.

Run script with android app

i've got this shell script:
#!system/bin/sh
while :
do
sync
echo 3> /proc/sys/vm/drop_caches
echo "Script is been launched"
sleep 30m
done
exit 0;
i wish run this script with an android app. I have already created a button with only a toast for now. How can i take the script (free.sh) and launch it with the button on the app? Or is there a solution to rewrite the code in java? Thanks

First, you will use Eclipse to create a simple Android helloworld app.
And add a button in your layout. This is very priliminary practise of Android development which you can dig a lot more from http://d.android.com
please try this code in your button's onclick call back function:
Button b = (Button)findViewById(R.id.buttonPower);
b.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
Process p=null;
try {
p = new ProcessBuilder()
.command("PathToYourScript")
.start();
} catch (IOException e) {
e.printStackTrace();
} finally {
if(p!=null) p.destroy();
}
}
});

Here is how you can run shell script from your android app
try {
Process process = Runtime.getRuntime().exec("sh /sdcard/test.sh");
BufferedReader in = new BufferedReader(new InputStreamReader(process.getInputStream()));
String listOfFiles = "";
String line;
while ((line = in.readLine()) != null) {
listOfFiles += line;
}
}
catch (IOException e) {
e.printStackTrace();
}

Well, now No errors (THANK YOU!) but do nothing..to try i've written a easy script that write a file.txt. See the code:
package com.mkyong.android;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;
import java.io.IOException;
import com.example.toast.R;
public class MainActivity extends Activity {
private Button button;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.tab1);
button = (Button) findViewById(R.id.button1);
button.setOnClickListener(new OnClickListener() {
#SuppressLint("SdCardPath")
#Override
public void onClick(View arg0) {
Process p=null;
try {
p = new ProcessBuilder()
.command("/sdcard/Script/scritturafile.sh")
.start();
} catch (IOException e) {
e.printStackTrace();
} finally {
if(p!=null) p.destroy();
}
}
});
}
}
The are no errors but when i press the button i think the shell doesn't go so don't create the file.txt

I've got errors in my code:
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;
import com.example.toast.R;
public class MainActivity extends Activity {
private Button button;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.tab1);
button = (Button) findViewById(R.id.button1);
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
Process process = new ProcessBuilder()
.command("PATH")
.redirectErrorStream(true)
.start();
try {
InputStream in = process.getInputStream();
OutputStream out = process.getOutputStream();
readStream(in);// Here: Syntax error, insert "}" to complete `Block`
finally {
process.destroy();
}
}
}
}); //Here: Syntax error on token "}", delete this token
}
protected void readStream(InputStream in) {
// TODO Auto-generated method stub
}
}

Android FTP Server

I am using the following code to make the android device a ftp server (Android Internal storage). I am getting the exception of os.android.NetworkOnMainThread. I have tried to put the onStart code in the AsyncTask but app never executes and crashes on launch. Any help regarding the ftp server on Android will be great as i have no idea how to get it working.
Here is the MainActivity Code
package com.googlecode.simpleftp;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.TextView;
import android.widget.Toast;
public class FTPServer extends Activity {
private static int COMMAND_PORT = 2121;
static final int DIALOG_ALERT_ID = 0;
private static ExecutorService executor = Executors.newCachedThreadPool();
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.my_menu, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
switch (item.getItemId()) {
case R.id.new_game:
System.out.println("New game button is pressed!");
//newGame();
return true;
case R.id.quit:
System.out.println("Quit button is pressed!");
showDialog(DIALOG_ALERT_ID);
return true;
default:
return super.onOptionsItemSelected(item); }
}
#Override
protected Dialog onCreateDialog(int id){
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Are you sure you want to exit?")
.setCancelable(false).setPositiveButton("yes", new DialogInterface.OnClickListener(){
#Override
public void onClick(DialogInterface dialog, int id){
FTPServer.this.finish();
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
return alert;
}
HEre is the ServerPI Code
import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
public class ServerPI implements Runnable{
private Socket clientSocket;
private BufferedReader in;
private PrintWriter out;
private String baseDir;
private String relativeDir;
private String absoluteDir;
private String fileName;
private String filePath;
public ServerPI(Socket incoming) throws IOException{
this.clientSocket = incoming;
in = new BufferedReader(new InputStreamReader(this.clientSocket.getInputStream()));
out = new PrintWriter(this.clientSocket.getOutputStream(), true);
baseDir = new File("").getAbsolutePath();
relativeDir = "/";
absoluteDir = baseDir + relativeDir;
fileName = "";
filePath = absoluteDir + "/" + fileName;
}
private void readCommandLoop() throws IOException {
String line = null;
reply(220, "Welcome to the SimpleFTP server!");
while((line = in.readLine()) != null){
int replyCode = executeCommand(line.trim());
if(replyCode == 221){
return;
}
}
}
private int executeCommand(String trim) {
// TODO Auto-generated method stub
return 0;
}
public int reply(int statusCode, String statusMessage){
out.println(statusCode + " " + statusMessage);
return statusCode;
}
#Override
public void run(){
try{
this.readCommandLoop();
} catch (IOException e){
e.printStackTrace();
}
finally {
try {
if(in != null){
in.close();
in = null;
}
if(out != null){
out.close();
out = null;
}
if (clientSocket != null){
clientSocket.close();
clientSocket = null;
}
}
catch (IOException e){
e.printStackTrace();
}
}
}
}
I have put the code in the AsyncTask, here it is
private class LongOperation extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... params) {
ServerSocket s = null;
Socket incoming = null;
try{
s = new ServerSocket(COMMAND_PORT);
String ip = (s.getInetAddress()).getHostAddress();
Context context = this.getApplicationContext();
CharSequence text = ip;
int duration = Toast.LENGTH_LONG;
Toast toast = Toast.makeText(context, text, duration);
Thread.sleep(1000);
toast.show();
while(true){
incoming = s.accept();
executor.execute(new ServerPI(incoming));
}
}
catch(Exception e){
System.out.println(e.toString());
e.printStackTrace();
}
finally{
try
{
if(incoming != null)incoming.close();
}
catch(IOException ignore)
{
//ignore
}
try
{
if (s!= null)
{
s.close();
}
}
catch(IOException ignore)
{
//ignore
}
}
return "Executed";
}
#Override
protected void onPostExecute(String result) {
}
#Override
protected void onPreExecute() {
}
#Override
protected void onProgressUpdate(Void... values) {
}
}
Iam calling the longOpertation in onCreate method. What is the problem that the app crashes on launch.
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fullscreen);
new LongOperation().execute();
}

Maybe because you didn't set up the permissions in the manifest? You've to set permission for internet usage.
If this doesn't work, please tell us which line is it throwing the exception.

while(true){ incoming = s.accept(); ...} You cannot put that in OnStart(). That should be done in a thread. So ServerSocket s = null; should be a variable of you activity.

So I went with Swiftp application (open source) as a service in my application which helped me to achieve my task. Thanks everyone who stepped forward to help. Here is the link if someone wants to follow

Please post your code here.
NetworkOnMainthreadException occurs because you maybe running Network related operation on the Main UI Thread. You should use asynctask for this purpose
This is only thrown for applications targeting the Honeycomb SDK or higher. Applications targeting earlier SDK versions are allowed to do networking on their main event loop threads, but it's heavily discouraged.
http://developer.android.com/reference/android/os/NetworkOnMainThreadException.html
class TheTask extends AsyncTask<Void,Void,Void>
{
protected void onPreExecute()
{ super.onPreExecute();
//display progressdialog.
}
protected void doInBackground(Void ...params)//return result here
{
//http request. do not update ui here
//call webservice
//return result here
return null;
}
protected void onPostExecute(Void result)//result of doInBackground is passed a parameter
{
super.onPostExecute(result);
//dismiss progressdialog.
//update ui using the result returned form doInbackground()
}
}
http://developer.android.com/reference/android/os/AsyncTask.html. Check the topic under the heading The 4 Steps.
A working example of asynctask # To use the tutorial in android 4.0.3 if had to work with AsynxTasc but i still dont work?.
The above makes a webserive call in doInBakckground(). Returns result and updates the ui by setting the result in textview in onPostExecute().

You can not do network operation in main thread in android 3.0 higher. Use AsyncTask for this network operation. See this for further explanation

Android Socket Getting Hanged

I have Created a Service Which in turn Creates a Socket, But as soon as try to read data sent from Server, it hangs ,On the other hand the same code run if i am not using Service but plain Activity ??
import android.app.*;
import android.content.*;
import android.os.*;
import android.util.*;
import java.net.*;
import java.io.*;
import android.widget.*;
public class BackgroundService extends Service
{
private Socket socket=null;
private InputStreamReader in=null;
private String ip;
private String tag="BackgroundService";
public IBinder onBind(Intent p1)
{
// TODO: Implement this method
return null;
}
public void onCreate(){
super.onCreate();
}
public void onStart(Intent i,int id){
super.onStart(i,id);
ip=i.getStringExtra("Ip");
Log.v(tag,"Ip "+i.getStringExtra("Ip"));
try
{
socket = new Socket(ip.trim(), 8888);
new Runnable() {
public void run()
{
// Hangs in this block.....
try
{
in = new InputStreamReader (socket.getInputStream());
BufferedReader bf=new BufferedReader (in);
// Never Reaches this messge
Log.v(tag,"mess:"+bf.readLine() );
}
catch (IOException e)
{
e.printStackTrace();
}
}
}.run();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}

Log.v is the Problem it wont allow you print the value so use System.out.println() and bf.printline will contain the message

Getting force close error in android when using threading

In my application i want to do bluetooth chat. I'm facing a problem in threading. In my application my android phone will work as server which has a blocking statement
socket=mServerSocket.accept();
for this purpose i've created a child thread so that it will run separately. But before finishing this child thread main thread goes down giving Force Close and if i use the .join() method it hangs up my UI.
What is the solution to run both threads parallel?
this is my code
main Activity
package com.my.bluechat_2_1;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class BlueChat extends Activity {
/** Called when the activity is first created. */
private BlueHandler btHandler=null;
private BluetoothAdapter btAdapter = null;
private Context context=this;
TextView chatWindow=null;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
chatWindow=(TextView)findViewById(R.id.textView1);
doStart();
}
private void doStart(){
Button btnStart=(Button)findViewById(R.id.button1);
btnStart.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View arg0) {
// Get local Bluetooth adapter
btAdapter = BluetoothAdapter.getDefaultAdapter();
// If the adapter is null, then Bluetooth is not supported
if(btAdapter == null)
{
Toast.makeText(context, "Device does not support Bluetooth", Toast.LENGTH_LONG).show();
}
if (!btAdapter.isEnabled()) {
Intent discoverableIntent = new
Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);
startActivity(discoverableIntent);
}
chatWindow.append("Waiting for connection...\n");
btHandler=new BlueHandler(context,chatWindow,btAdapter);
Thread acceptThread=new Thread(btHandler);
acceptThread.start();
}
});
}
}
BlueHandler
package com.my.bluechat_2_1;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.UUID;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothServerSocket;
import android.bluetooth.BluetoothSocket;
import android.content.Context;
import android.widget.TextView;
import android.widget.Toast;
public class BlueHandler implements Runnable{
// Name for the SDP record when creating server socket
private static final String SMARTCAM_BT_SERVICE_NAME = "SmartCam";
// Unique UUID for this application
private static final UUID SMARTCAM_BT_SERVICE_UUID = UUID.fromString("95b82690-4c94-11e1-b86c-0800200c9a66");
private BluetoothAdapter btAdapter = null;
private BluetoothServerSocket btServerSocket = null;
private BluetoothSocket btSocket = null;
private InputStream btInputStream=null;
private Context contextObj=null;
private TextView textView;
public BlueHandler(Context contextObj,TextView textView,BluetoothAdapter btAdapter){
this.contextObj=contextObj;
this.btAdapter=btAdapter;
this.textView=textView;
try {
btServerSocket=this.btAdapter.listenUsingRfcommWithServiceRecord(SMARTCAM_BT_SERVICE_NAME, SMARTCAM_BT_SERVICE_UUID);
} catch (IOException e) {
// TODO Auto-generated catch block
Toast.makeText(this.contextObj, "Service not created", Toast.LENGTH_LONG);
}
}
#Override
public void run() {
// TODO Auto-generated method stub
textView.append("Inside child thread.\n");
textView.append(btServerSocket+"\n");
while (true) {
try {
btSocket = btServerSocket.accept();
} catch (IOException e) {
break;
}
// If a connection was accepted
if (btSocket != null) {
// Do work to manage the connection (in a separate thread)
try {
btServerSocket.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
break;
}
}
textView.append("Connected.\n");
try {
btInputStream=btSocket.getInputStream();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
byte[] buffer = new byte[1024]; // buffer store for the stream
String s;
int bytes; // bytes returned from read()
// Keep listening to the InputStream until an exception occurs
while (true) {
try {
// Read from the InputStream
bytes=btInputStream.read(buffer);
s= new String(buffer);
// Send the obtained bytes to the UI Activity
textView.append("received ::" +s+"\n");
} catch (IOException e) {
break;
}
}
}
}

You're probably getting a crash because you're accessing a textView on the worker thread. You'll need to use TextView.post(Runnable) to make that not happen.
In reality you should be using a bindable Service to do this kind of work. You can post back to the UI via broadcast intents or callback methods, That way you don't have to worry about rotation bugs.

Are you performing a long operation in the constructor of your children thread? Each long operation must be done in the run() method.