Develop Reference

How to send message from server to client (TCP , android applications)

I had created two android applications connected with sockets. Client sends an image to server and Server displays it. when you touch the image on server, it gets its coordinates,this is working now. what I need is that server sends the coordinates to the client, but I dont know how to send them to client and retrieve them, should I open a new socket ? I have no idea how to do this. Can somebody give me a hand please?
This is my code so far
SERVER
package com.example.serverlate;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Handler;
import android.util.DisplayMetrics;
import android.widget.ImageView;
import android.widget.TextView;
public class ServerLate extends Activity {
private ServerSocket serverSocket;
String touchedCoordinates;
Handler updateConversationHandler;
Thread serverThread = null;
private ImageView imageView;
public static final int SERVERPORT = 6000;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_server_late);
imageView=(ImageView) findViewById(R.id.imageViewServer);
updateConversationHandler = new Handler();
this.serverThread = new Thread(new ServerThread());
this.serverThread.start();
}
#Override
protected void onStop() {
super.onStop();
try {
serverSocket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
class ServerThread implements Runnable {
public void run() {
Socket socket = null;
try {
serverSocket = new ServerSocket(SERVERPORT);
} catch (IOException e) {
e.printStackTrace();
}
while (!Thread.currentThread().isInterrupted()) {
try {
socket = serverSocket.accept();
CommunicationThread commThread = new CommunicationThread(socket);
new Thread(commThread).start();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
class CommunicationThread implements Runnable {
private Socket clientSocket;
private DataInputStream input;
public CommunicationThread(Socket clientSocket) {
this.clientSocket = clientSocket;
try {
InputStream in = this.clientSocket.getInputStream();
this.input = new DataInputStream(in);
} catch (IOException e) {
e.printStackTrace();
}
}
public void run() {
while (!Thread.currentThread().isInterrupted()) {
try {
byte[] data;
int len= this.input.readInt();
data = new byte[len];
if (len > 0) {
this.input.readFully(data,0,data.length);
}
updateConversationHandler.post(new updateUIThread(data));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
class updateUIThread implements Runnable {
private byte[] byteArray;
public updateUIThread(byte[] array){
this.byteArray=array;
}
#Override
public void run() {
Bitmap bitmap = BitmapFactory.decodeByteArray(byteArray , 0, byteArray .length);
imageView.setImageBitmap(bitmap);
imageView.setOnTouchListener(new View.OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
touchedCoordinates="Touch coordinates : " +
String.valueOf(event.getX()) + " x " + String.valueOf(event.getY());
return true;
}
});
}
}
}
CLIENT
package com.example.clientlate;
import java.io.BufferedWriter;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import java.nio.ByteBuffer;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Bitmap.CompressFormat;
import android.graphics.drawable.BitmapDrawable;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageView;
public class ClientLate extends Activity {
private Socket socket;
private static final int SERVERPORT = 5000;
private static final String SERVER_IP = "10.0.2.2";
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_client_late);
new Thread(new ClientThread()).start();
}
public void onClick(View view) {
try {
ImageView imageView=(ImageView) findViewById(R.id.imageView1);
Bitmap bmp=((BitmapDrawable)imageView.getDrawable()).getBitmap();
ByteArrayOutputStream bos = new ByteArrayOutputStream();
bmp.compress(CompressFormat.PNG, 0 /*ignored for PNG*/, bos);
byte[] array = bos.toByteArray();
OutputStream out = socket.getOutputStream();
DataOutputStream dos = new DataOutputStream(out);
dos.writeInt(array.length);
dos.write(array, 0, array.length);
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
class ClientThread implements Runnable {
#Override
public void run() {
try {
InetAddress serverAddr = InetAddress.getByName(SERVER_IP);
socket = new Socket(serverAddr, SERVERPORT);
} catch (UnknownHostException e1) {
e1.printStackTrace();
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
}

You can try something like this in client side :
public class ClientLate extends Activity {
public void onCreate(Bundle savedInstanceState) {
....
updateConversationHandler = new Handler();
FPSHandler = new Handler();
new Thread(new ClientThread()).start();
....
}
class ClientThread implements Runnable {
#Override
public void run() {
thread1=Thread.currentThread();
try {
InetAddress serverAddr = InetAddress.getByName(SERVER_IP);
socketTE = new Socket(serverAddr, SERVERPORT);
CommunicationThread commThread = new CommunicationThread(socketTE);
new Thread(commThread).start();
} catch (UnknownHostException e1) {
Toast.makeText(getApplicationContext(), "Connection failed",
Toast.LENGTH_SHORT).show();
finish();
} catch (IOException e1) {
Toast.makeText(getApplicationContext(), "Connection failed",
Toast.LENGTH_SHORT).show();
finish();
}
}
}
class CommunicationThread implements Runnable
{
private Socket clientSocket;
private BufferedReader input;
public CommunicationThread(Socket clientSocket)
{
thread2=Thread.currentThread();
this.clientSocket = clientSocket;
try {
this.input = new BufferedReader(new InputStreamReader(this.clientSocket.getInputStream()));
} catch (IOException e) {
e.printStackTrace();
}
}
public void run()
{
while (running.get())
{
try
{
String read = input.readLine();
updateConversationHandler.post(new updateUIThread(read));
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
class updateUIThread implements Runnable
{
private String msg;
public updateUIThread(String str)
{
this.msg = str;
}
#Override
public void run()
{
...
}
}
....
}

Android device to Server text send

I am trying to send a string from an android device to the server using the code following:
package com.example.androidsocketserver;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
public class MainActivity extends Activity {
private Socket socket;
private static final int SERVERPORT = 6000;
private static final String SERVER_IP = "10.50.27.10";
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new Thread(new ClientThread()).start();
}
public void onClick(View view) {
try {
EditText et = (EditText) findViewById(R.id.EditText01);
String str = et.getText().toString();
PrintWriter out = new PrintWriter(new BufferedWriter(
new OutputStreamWriter(socket.getOutputStream())),
true);
out.println(str);
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
class ClientThread implements Runnable {
#Override
public void run() {
try {
InetAddress serverAddr = InetAddress.getByName(SERVER_IP);
socket = new Socket(serverAddr, SERVERPORT);
} catch (UnknownHostException e1) {
e1.printStackTrace();
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
}
But it is sending the string only on first click. In second time it is unable to send the content. What I need to do?

But it is sending the string only on first click. In second time it is
unable to send the content. What I need to do?
Put new Thread(new ClientThread()).start(); in a separate method say:
startThread(){
new Thread(new ClientThread()).start();
}
and then call this method in onClick

Applications crashes in 3.0 but works fine in 2.3.3

Hi guys im trying to create a application that uses a socket connection i was going across some examples, the piece of code below works fine when i run it on 2.3.3 and the same crashes in 3.0.
package com.simple.client;
import android.app.Activity;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.os.Bundle;
public class SimpleClientActivity extends Activity {
EditText textOut;
TextView textIn;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
textOut = (EditText)findViewById(R.id.textout);
Button buttonSend = (Button)findViewById(R.id.send);
textIn = (TextView)findViewById(R.id.textin);
buttonSend.setOnClickListener(buttonSendOnClickListener);
}
Button.OnClickListener buttonSendOnClickListener
= new Button.OnClickListener(){
public void onClick(View arg0) {
// TODO Auto-generated method stub
Socket socket = null;
DataOutputStream dataOutputStream = null;
DataInputStream dataInputStream = null;
try {
socket = new Socket("172.16.2.172", 8899);
dataOutputStream = new DataOutputStream(socket.getOutputStream());
dataInputStream = new DataInputStream(socket.getInputStream());
dataOutputStream.writeUTF(textOut.getText().toString());
textIn.setText(dataInputStream.readUTF());
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
e.printStackTrace();
}
finally{
if (socket != null){
try {
socket.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (dataOutputStream != null){
try {
dataOutputStream.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (dataInputStream != null){
try {
dataInputStream.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}};
}
I have tried all but not able to figure out what is happening,

My guess is, the error caused by StrictMode.ThreadPolicy. In android 3.0, you can't access network in the same UI thread.

Do you have multiple resource folders for your layouts? if yes, maybe you do not have its related layout.

A simple client-server - Android<>PC

I am testing socket programming on Android however I am having a problem. The client is basically launched through the main activity with a basic function of sending a message to the server and getting a reply.
the client activity:
package com.test.socket;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class socketActivity extends Activity implements OnClickListener {
String input;
private EditText et;
private ObjectOutputStream oos;
private TextView tv;
private String message;
private ObjectInputStream ois;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
try{
InetAddress host = InetAddress.getLocalHost();
Socket socket = new Socket(host.getHostName(),7777);
//send to server
oos = new ObjectOutputStream(socket.getOutputStream());
et = (EditText) findViewById(R.id.text);
Button sendButton = (Button) findViewById(R.id.button);
sendButton.setOnClickListener(this);
//read from server
ois = new ObjectInputStream(socket.getInputStream());
//System.out.println("Message from Server: "+message);
tv = (TextView) findViewById(R.id.textView);
}
catch(UnknownHostException e)
{
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch(v.getId())
{
case R.id.button:
input = et.getText().toString();
try {
oos.writeObject(input);
ois.close();
oos.close();
message = (String) ois.readObject();
tv.setText("Message from Server: "+message);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
break;
}
}
}
The Server class launched separately from JCreator listening to port 7777:
import java.io.*;
import java.lang.*;
import java.net.*;
public class server {
private ServerSocket server;
private int port = 7777;
public server()
{
try{
server = new ServerSocket(port);
}
catch(IOException e)
{
e.printStackTrace();
}
}
public static void main(String args[])
{
server example = new server();
example.handleConnection();
}
public void handleConnection()
{
System.out.println("Waiting for client message...");
while(true)
{
try{
Socket socket = server.accept();
new ConnectionHandler(socket);
}
catch(IOException e)
{
e.printStackTrace();
}
}
}
}
ConnectionHandler class which the Server accesses:
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.Socket;
public class ConnectionHandler implements Runnable {
private Socket socket;
public ConnectionHandler(Socket socket)
{
this.socket = socket;
Thread t = new Thread(this);
t.start();
}
#Override
public void run() {
// TODO Auto-generated method stub
try{
//receive from client
ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
String message = (String) ois.readObject();
System.out.println("Message from client: "+message);
if(message.equals("check"))
{
System.out.println("Checking for malicious interference...");
Thread.sleep(5000);
System.out.println("Status: Files are good.");
}
//send response to client
ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
if(message.equals("check"))
{
oos.writeObject("Checking...");
}
else oos.writeObject("Invalid input");
ois.close();
oos.close();
socket.close();
System.out.println("Waiting for client message...");
}
catch(IOException e)
{
e.printStackTrace();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
I have tested the code on JCreator and Eclipse through Java application not Android app and it worked perfect. However when I try doing it through the activity, it's not working.
Any ideas?

In Android, localhost would point to the phone/emulator itself. It doesn't point to your server. The following line below is pointing to your Android device/emulator and not your server. You need to get the actual IP of the server to get it working from your Android
InetAddress host = InetAddress.getLocalHost();
Socket socket = new Socket(host.getHostName(),7777);
It works through Java App, because when you execute it from the context of Java Application, the localhost is pointing to the same server location.

Problem opening a Socket

I'm building a very small app to send data from the cellphone to a computer. I've read a couple of examples and got the server and client code working. But when i try to connect them, got a "network unreachable" error. Any idea what am i doing wrong??
This is the Server Code:
import java.net.*;
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.*;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class Server {
static BufferedReader in = null;
static Socket clientSocket = null;
static ServerSocket serverSocket = null;
public static void main(String[] args) throws IOException {
JFrame frame = new JFrame("FrameDemo");
frame.addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
try {
if (in != null)
in.close();
if (serverSocket.isClosed())
{}
else
serverSocket.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}
});
JLabel Label = new JLabel("");
Label.setPreferredSize(new Dimension(175, 100));
frame.getContentPane().add(Label, BorderLayout.CENTER);
//Display the window.
frame.pack();
frame.setVisible(true);
Label.setText("Empezo");
serverSocket = null;
try {
serverSocket = new ServerSocket(4444);
} catch (IOException e) {
System.err.println("Could not listen on port: 4444.");
System.err.println(e.getMessage());
System.exit(1);
}
Integer puerto = serverSocket.getLocalPort();
Label.setText("<html>Puerto Abierto: " + puerto.toString() + "<br>IP Servidor: " + serverSocket.getInetAddress().toString() + "</html>");
clientSocket = null;
try {
clientSocket = serverSocket.accept();
Label.setText("Conection Accepted");
} catch (IOException e) {
System.err.println("Accept failed.");
System.exit(1);
}
in = new BufferedReader(
new InputStreamReader(
clientSocket.getInputStream()));
while ((in.readLine()) != null) {
System.out.println("Mensaje: " + in.readLine());
}
}
}
And the Cliente part
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;
public class PruebaSocket extends Activity {
/** Called when the activity is first created. */
Socket Skt;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button Enviar =(Button)findViewById(R.id.OK);
Button Salir = (Button)findViewById(R.id.SALIR);
final TextView IP = (TextView)findViewById(R.id.IP);
Skt = new Socket();
Enviar.setOnClickListener(new OnClickListener(){
public void onClick(View v) {
try{
Skt = new Socket("192.168.1.101",4444);
CharSequence errorMessage = "Coneccted";
Toast.makeText(PruebaSocket.this, errorMessage, Toast.LENGTH_SHORT).show();
}
catch(Exception E)
{
CharSequence errorMessage = E.getMessage();
Toast.makeText(PruebaSocket.this, errorMessage, Toast.LENGTH_SHORT).show();
if (Skt.isConnected())
try {
Skt.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
});
Salir.setOnClickListener(new OnClickListener(){
#Override
public void onClick(View arg0) {
try {
Skt.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
);
}
}
192.168.1.101 it's the IP of the server.

I don't know much about java sockets but the normal usage of a socket is: create, bind, and put in listen mode (udp) or call .accept() (tcp). I can see Java also has the binding phase - http://download.oracle.com/javase/1.5.0/docs/api/java/net/ServerSocket.html#bind(java.net.SocketAddress, int).