android client-java server communication

Question

We are developing an android application.It basically involves client server communication.Client is android phone and server is java.Client and server communication takes place.It is expected that client sends a message to the server and server responds back to the client.But in reality client is able to send the message to the server but server is unable or sends an incorrect response.I don't understand why is it happening. Here is the client code(android):

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.os.AsyncTask;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;


public class MainActivity extends Activity {
private Socket client;
private PrintWriter printwriter;
private EditText textField;
public TextView accept;
private Button button;
private String message;
private static BufferedReader bufferedReader;
public static InputStreamReader inputStreamReader;
String response;
DataInputStream dis;
static String Extra_message = "hkrw.clientside";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    textField = (EditText) findViewById(R.id.editText1);
    button = (Button) findViewById(R.id.button1);
    this.accept = (TextView) findViewById(R.id.accept);


    button.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            message = textField.getText().toString();
            textField.setText("");
            SendMessage sendMessageTask = new SendMessage();
            sendMessageTask.execute();
            accept.setText(response);
        }
    });
}

private class SendMessage extends AsyncTask<Void, Void, Void> {
    @Override
    protected Void doInBackground(Void... params) {
        DataOutputStream dataOutputStream = null;
        DataInputStream smalldataInputStream = null;
        try {
            client = new Socket("192.168.1.6", 4446);
            printwriter = new PrintWriter(client.getOutputStream(), true);
            inputStreamReader = new InputStreamReader(client.getInputStream());
            bufferedReader = new BufferedReader(inputStreamReader);
            printwriter.write(message);
           // smalldataInputStream = new DataInputStream(client.getInputStream());

            printwriter.flush();
            printwriter.close();
            //dis= new DataInputStream(client.getInputStream());
            //response=dis.readUTF();
           response = bufferedReader.toString();
            client.getInputStream();

          // client.shutdownInput();
           // client.shutdownOutput();
           client.close();

        } catch (UnknownHostException e) {
            e.printStackTrace();

        } catch (IOException e) {
            e.printStackTrace();
        }

        return null;
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

        return super.onOptionsItemSelected(item);
    }
}

Here is the code of the new activity which I have created in client side.

 import android.app.Activity;
 import android.content.Intent;
 import android.os.Bundle;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.widget.TextView;


 public class respond extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_respond);
    Intent intent=getIntent();
    String message = intent.getStringExtra(MainActivity.Extra_message);
    TextView response;
    response= (TextView) findViewById(R.id.textView1);
    response.setText(message);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_respond, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

       return super.onOptionsItemSelected(item);
   }
}

Here is the server code in java:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
import java.io.PrintWriter;
import java.io.OutputStreamWriter;
import java.io.FileOutputStream;
import java.io.DataOutputStream;





public class Server {

private static ServerSocket serverSocket;
private static Socket clientSocket;
private static InputStreamReader inputStreamReader;
private static BufferedReader bufferedReader;
private static String message;
    private static PrintWriter printwriter ;
    static DataOutputStream dos;


    public static void main(String[] args) {
        String w="Hello World";


        try {
        serverSocket = new ServerSocket(4446); // Server socket

    } catch (IOException e) {
        System.out.println("Could not listen on port: 4444");
    }

    System.out.println("Server started. Listening to the port 4446");

    while (true) {
        try {

            clientSocket = serverSocket.accept(); // accept the client connection
            inputStreamReader = new InputStreamReader(clientSocket.getInputStream());
            bufferedReader = new BufferedReader(inputStreamReader); // get the client message
            message = bufferedReader.readLine();

            System.out.println(message);



                            dos=new DataOutputStream(clientSocket.getOutputStream());

                            dos.writeUTF(w);
                            clientSocket.close();
                            System.out.println(dos);


                            inputStreamReader.close();



        } catch (IOException ex) {
            System.out.println("Problem in message reading");
        }
    }

            }

}

What is the input and what output was received as incorrect ? — Prabindh
– Prabindh, Commented Jan 28, 2016 at 4:04
Any message from server to client and then server responds with a message to the cient — parth
– parth, Commented Jan 28, 2016 at 4:09
Sorry for the mistake, client first sends a message to the server, the server then responds back to the client with a message — parth
– parth, Commented Jan 28, 2016 at 4:11

Yesyoor · Accepted Answer · 2016-01-28 04:22:53Z

this example sends a message to the server (pc in wlan), and then gets the message back from server to phone, changing text accordingly.

change ip address of server to your pc address in wlan, make sure to start server first, then phone app, being in that wlan

Server:

public class ChatServer implements Runnable{

private Socket socket = null;
private ServerSocket server = null;
private Thread       thread = null;

private DataInputStream streamIn  =  null;
private DataOutputStream streamOut = null;


int port;
boolean done ;

public ChatServer(){
    port = 6668;
    try{
        System.out.println("Gewählter Port: " + port + ", bitte warte...");
        server = new ServerSocket(port);
        System.out.println("Server gestartet: " + server);
        start();
    }
    catch(IOException ioe)
    {
        System.out.println(ioe);
    }
}
public void start(){
    if (thread == null){
        thread = new Thread(this);
        thread.start();
    }
}

public void run(){
    while (thread != null){
        try{
            System.out.println("waiting for Client ...");
            socket = server.accept();
            System.out.println("Client accepted: " + socket + " IP: "+ socket.getInetAddress());
            System.out.println("connecting ...");
            open();
            done = false;

            while (!done){
                try{
                    String line = streamIn.readUTF();
                    System.out.println(line);
                    send("Server recieved :"+line);
                    done = line.equals(".bye");
                }
                catch(IOException ioe){
                    done = true;
                    ioe.printStackTrace();
                }
            }
            close();
        }
        catch(IOException ie){
            System.out.println("Acceptance Error: " + ie);
        }
    }
}
public void send(String msg)
{
    try
    {
        if(msg != null) {
            streamOut.writeUTF(msg);
            streamOut.flush();
        }
    }
    catch(IOException ioe)
    {
        ioe.printStackTrace();
    }
}
public void open() throws IOException{
    streamIn  = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
    streamOut = new DataOutputStream(socket.getOutputStream());
}
public void close() throws IOException{
    if (socket != null)    socket.close();
    if (streamIn != null)  streamIn.close();
    if (streamOut != null)  streamOut.close();

}
@SuppressWarnings("deprecation")
public void stop(){
    if (thread != null){
        thread.stop();
        thread = null;
    }
}


}

client:

public class MainActivity extends Activity implements Runnable{

EditText textUnten;
Button button;
ChatProzKlasse chat;
public static String puffer;
public static String messages;
public static TextView textMitte;
Thread thread;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    textMitte = (TextView) findViewById (R.id.textMitteID);
    textUnten = (EditText) findViewById (R.id.textUntenID);
    button = (Button) findViewById(R.id.sendButton);

    messages = "";



    chat = new ChatProzKlasse();
    thread = new Thread(this);

    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            chat.client.send(textUnten.getText().toString());
            textUnten.setText("");



        }
    });
    thread.start();


}

public  void setTextMitte(){
    runOnUiThread(new Runnable() {
        @Override
        public void run() {
            textMitte.setText(messages);
        }
        });


}
@Override
protected void onResume() {
    super.onResume();



}

@Override
public void run() {
    while(true) {
        setTextMitte();
        try {
            thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}


}
public class ChatClient {

private Socket socket              = null;

private DataInputStream console    = null;
private DataOutputStream streamOut = null;
private DataInputStream streamIn = null;
public static boolean isconnected = false;

public ChatClient(String serverName, int serverPort){
    System.out.println("Verbindungsaufbau. Bitte warten ...");
    try{
        socket = new Socket(serverName, serverPort);
        Log.d("DEBUG", "Connected: " + socket);
        if(socket != null) {
            start();
        }
    }
    catch(UnknownHostException uhe){
        Log.d("DEBUG","Host unknown: " + uhe.getMessage());
    }
    catch(IOException ioe){
        Log.d("DEBUG","Unexpected exception: " + ioe.getMessage());
    }

}

public void start() throws IOException
{
    console   = new DataInputStream(System.in);
    streamOut = new DataOutputStream(socket.getOutputStream());
    isconnected = true;

}

public void stop(){
    try{
        if (console   != null)  console.close();
        if (streamOut != null)  streamOut.close();
        if (socket    != null)  socket.close();
    }
    catch(IOException ioe){
        System.out.println("Error closing ...");
    }
}
public void open() throws IOException{
    streamIn  = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
}
public void close() throws IOException{
    if (socket != null)    socket.close();
    if (console != null)  console.close();
}

public void send(String msg)
{
    try
    {
        if(msg != null) {
            streamOut.writeUTF(msg);
            streamOut.flush();
        }
    }
    catch(IOException ioe)
    {
        Log.d("DEBUG","Sending error: " + ioe.getMessage());
    }
}

public void recieve(){
    try{
        open();
        boolean done = false;

        while (!done){
            try{
                String line = streamIn.readUTF();
                if(!(line.equals(""))) {
                    MainActivity.messages =line;
                    MainActivity.puffer = line;
                }
                System.out.println(" " + line);
                done = line.equals(".bye");
            }
            catch(IOException ioe){
                done = true;
                ioe.printStackTrace();
            }
        }
        close();
    }
    catch(IOException ie){
        System.out.println("Acceptance Error: " + ie);
    }
}



}



public class ChatProzKlasse implements Runnable {
Thread thread;
ChatClient client;

public ChatProzKlasse(){
    thread = new Thread(this);
    thread.start();

}

@Override
public synchronized void run() {

    if(client == null) {
        try {
            System.out.println(" trying new Client");
            client = new ChatClient("192.168.1.111", 6668);


        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    if (client !=null){
        if(client != null && ChatClient.isconnected) {
            client.recieve();
        }
    }

}}

the client consists of 3 separate classes i just have put them underneath here, make sure to also start a new Chatserver() on main (string[]args)
Thanks again for the code.But i am getting errors.Where is the main() function in server code?I am also getting error at thread.stop() in server side.I have not yet executed the client side.Also what is the return type of the function chatserver() in server?
I upvoted it but as I am still a new user it doesnt consider my vote.

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