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Send a string through WiFi-Direct between two android devices

It is now over a month that I'm trying to send a string using WiFi-Direct between two android devices, but I'm still struggling hard to understand what I'm doing wrong.
I've looked around forums but they often don't give much detail on how to achieve what I want.
I also went through those two guides from the android developer's website:
Create P2P connections with Wi-Fi Direct
Wi-Fi Direct (peer-to-peer or P2P) overview
I'm using one activity - ActivityConnection - where I toggle the visibility of views depending on whether the user previously chose to send or to receive the string.
Immediatly, on the client side, discoverPeers() looks for any device with WiFi-Direct turned on and displays them on a ListView. Once the user chooses a device and presses the send button, the connection makes itself and the string is sent.
On the server side, the server is immediatly launched using my AsyncServerTask class. There, it waits for a client to connect and to retrieve its sent string.
My main problem is that, after choosing the device and tapping on the send button, the server side isn't receiving anything.
My second problem is that, sometimes, devices aren't being discovered and the listview stays empty.
Am I missing something? Or maybe doing something wrong?
Here's my current code.
I took the liberty to get rid of any line I thought to be out of context to make it easier to read.
ActivityConnection
public class ActivityConnection extends AppCompatActivity implements NewPeersListener {
public static final String CONNECTION_ACTOR = "actor";
public static final String SEND_INFO = "send";
public static final String RECEIVE_INFO = "receive";
ListView listViewDevices;
private IntentFilter intentFilter;
private WifiP2pManager manager;
private WifiP2pManager.Channel channel;
private WiFiDirectBroadcastReceiver receiver;
public List <WifiP2pDevice> listDevices;
private WifiP2pDevice selectedDevice;
#Override
public void onCreate (Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
confirm.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
connectToSelectedDevice();
}
});
Intent intent = this.getIntent();
String actor = intent.getStringExtra(CONNECTION_ACTOR);
this.intentFilter = new IntentFilter();
this.intentFilter.addAction(WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION);
this.intentFilter.addAction(WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION);
this.intentFilter.addAction(WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION);
this.intentFilter.addAction(WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION);
this.manager = (WifiP2pManager) this.getSystemService(Context.WIFI_P2P_SERVICE);
this.channel = this.manager.initialize(this, this.getMainLooper(), null);
this.receiver = new WiFiDirectBroadcastReceiver(this.manager, this.channel, this);
this.listDevices = new ArrayList <> ();
if (actor.equals(SEND_INFO)) {
DeviceAdapter adapter = new DeviceAdapter(ActivityConnection.this, R.layout.device_item, this.listDevices);
this.listViewDevices.setAdapter(adapter);
this.listViewDevices.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectedDevice = listDevices.get(position);
}
});
this.discoverPeers();
}
else if (actor.equals(RECEIVE_INFO)) {
new ServerAsyncTask(this).execute();
}
}
#Override
protected void onResume() {
super.onResume();
this.receiver = new WiFiDirectBroadcastReceiver(this.manager, this.channel, this);
this.registerReceiver(this.receiver, this.intentFilter);
}
#Override
protected void onPause() {
super.onPause();
this.unregisterReceiver(this.receiver);
}
public void resultReceived (String result) {
Toast.makeText(ActivityConnection.this, "Received! :)", Toast.LENGTH_SHORT).show();
}
private void discoverPeers () {
manager.discoverPeers(channel, new WifiP2pManager.ActionListener() {
#Override
public void onSuccess() {
// The discovery process succeeded
}
#Override
public void onFailure(int reason) {
// The discovery process DID NOT succeed
Toast.makeText(ActivityConnection.this, "Discovery process DID NOT succeed. Please verify that WiFi-Direct is active.", Toast.LENGTH_LONG).show();
}
});
}
private void connectToSelectedDevice () {
WifiP2pConfig config = new WifiP2pConfig();
config.deviceAddress = this.selectedDevice.deviceAddress;
this.manager.connect(this.channel, config, new WifiP2pManager.ActionListener() {
#Override
public void onSuccess() {
// Send string
Intent serviceIntent = new Intent(ActivityConnection.this, TransferService.class);
serviceIntent.setAction(TransferService.ACTION_SEND_STRING);
serviceIntent.putExtra(TransferService.EXTRAS_GROUP_OWNER_ADDRESS, getMacAddress());
serviceIntent.putExtra(TransferService.EXTRAS_GROUP_OWNER_PORT, 8090);
startService(serviceIntent);
onBackPressed();
}
#Override
public void onFailure(int reason) {
Toast.makeText(ActivityConnection.this, "Connection failed. Try again.", Toast.LENGTH_SHORT).show();
}
});
}
#NonNull
private String getMacAddress () {
try {
List <NetworkInterface> all = Collections.list(NetworkInterface.getNetworkInterfaces());
for (NetworkInterface nif : all) {
if (!nif.getName().equalsIgnoreCase("wlan0")) continue;
byte[] macBytes = nif.getHardwareAddress();
if (macBytes == null) {
return "";
}
StringBuilder result = new StringBuilder();
for (byte b : macBytes) {
result.append(String.format("%02X:",b));
}
if (result.length() > 0) {
result.deleteCharAt(result.length() - 1);
}
return result.toString();
}
} catch (Exception e) {
}
return "02:00:00:00:00:00";
}
#Override
public void newPeers (WifiP2pDeviceList wifiP2pDeviceList) {
this.listDevices = new ArrayList <> (wifiP2pDeviceList.getDeviceList());
DeviceAdapter adapter = new DeviceAdapter(ActivityConnection.this, R.layout.device_item, this.listDevices);
this.listViewDevices.setAdapter(adapter);
}
}
WiFiDirectBroadcastReceiver
public class WiFiDirectBroadcastReceiver extends BroadcastReceiver {
private WifiP2pManager manager;
private WifiP2pManager.Channel channel;
private ActivityConnection activity;
private List <NewPeersListener> listeners;
public WiFiDirectBroadcastReceiver(WifiP2pManager manager, WifiP2pManager.Channel channel, ActivityConnection activity) {
super();
this.manager = manager;
this.channel = channel;
this.activity = activity;
this.listeners = new ArrayList <> ();
this.listeners.add(activity);
}
#Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION.equals(action)) {
int state = intent.getIntExtra(WifiP2pManager.EXTRA_WIFI_STATE, -1);
if (state == WifiP2pManager.WIFI_P2P_STATE_ENABLED) {
// Wi-Fi P2P is enabled
} else {
// Wi-Fi P2P is not enabled
Toast.makeText(this.activity, "Please turn on WiFi-Direct (or WiFi-P2P).", Toast.LENGTH_SHORT).show();
}
} else if (WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION.equals(action)) {
// Request available peers from the wifi p2p manager.
if (this.manager != null) {
this.manager.requestPeers(this.channel, new WifiP2pManager.PeerListListener() {
#Override
public void onPeersAvailable(WifiP2pDeviceList peers) {
for (NewPeersListener listener : listeners) {
listener.newPeers(peers);
}
}
});
}
} else if (WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION.equals(action)) {
// Respond to new connection or disconnections
} else if (WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION.equals(action)) {
// Respond to this device's wifi state changing
}
}
}
ServerAsyncTask (server)
public class ServerAsyncTask extends AsyncTask<Void, Void, String> {
private ServerSocket serverSocket;
private Socket clientSocket;
private DataInputStream stream;
private WeakReference <Context> contextWeakReference;
ServerAsyncTask (Context context) {
this.contextWeakReference = new WeakReference <> (context);
}
#Override
protected String doInBackground (Void... params) {
try {
this.serverSocket = new ServerSocket(8090);
this.clientSocket = this.serverSocket.accept();
this.stream = new DataInputStream(this.clientSocket.getInputStream());
String received = this.stream.readUTF();
this.serverSocket.close();
return received;
} catch (IOException e) {
Log.e(TransferService.TAG, Objects.requireNonNull(e.getMessage()));
return null;
} finally {
if (this.stream != null) {
try {
this.stream.close();
} catch (IOException e) {
Log.e(TransferService.TAG, Objects.requireNonNull(e.getMessage()));
}
}
if (this.clientSocket != null) {
try {
this.clientSocket.close();
} catch (IOException e) {
Log.e(TransferService.TAG, Objects.requireNonNull(e.getMessage()));
}
}
if (this.serverSocket != null) {
try {
this.serverSocket.close();
} catch (IOException e) {
Log.e(TransferService.TAG, Objects.requireNonNull(e.getMessage()));
}
}
}
}
/*
* (non-Javadoc)
* #see android.os.AsyncTask#onPostExecute(java.lang.Object)
*/
#Override
protected void onPostExecute (String result) {
super.onPostExecute(result);
((ActivityConnection) this.contextWeakReference.get()).resultReceived(result);
}
}
TransferService (client)
public class TransferService extends IntentService {
public static final String TAG = "WIFI_DIRECT";
private static final int SOCKET_TIMEOUT = 5000;
public static final String ACTION_SEND_STRING = "sendString";
public static final String EXTRAS_GROUP_OWNER_ADDRESS = "go_host";
public static final String EXTRAS_GROUP_OWNER_PORT = "go_port";
public TransferService (String name) {
super(name);
}
public TransferService () {
super("TransferService");
}
#Override
protected void onHandleIntent (Intent intent) {
Context context = getApplicationContext();
if (intent.getAction().equals(ACTION_SEND_STRING)) {
String toSend = "string to send";
String host = intent.getExtras().getString(EXTRAS_GROUP_OWNER_ADDRESS);
int port = intent.getExtras().getInt(EXTRAS_GROUP_OWNER_PORT);
Socket socket = null;
DataOutputStream stream = null;
try {
// Create a client socket with the host, port, and timeout information.
socket = new Socket();
socket.bind(null);
socket.connect((new InetSocketAddress(host, port)), SOCKET_TIMEOUT);
Log.d(TAG, "Client connected socket - " + socket.isConnected());
// Send string
stream = new DataOutputStream(socket.getOutputStream());
stream.writeUTF(toSend);
stream.close();
Toast.makeText(context, "Sent! :)", Toast.LENGTH_SHORT).show();
} catch (IOException e) {
Log.e(TAG, Objects.requireNonNull(e.getMessage()));
} finally {
if (stream != null) {
try {
stream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (socket != null) {
if (socket.isConnected()) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
}
}

In the ActivityConnetion class, I was giving a MAC address instead of an IP address. I don't know why I didn't see this, nor why I did it in the first place. So I looked around this forum and found out how to get the IP address of the WiFi-Direct's group owner: Wifi Direct Group Owner Address .
To get the code running, I went into the ActivityConnetion class, delete the getMacAddress() method and replaced this line:
serviceIntent.putExtra(TransferService.EXTRAS_GROUP_OWNER_ADDRESS, getMacAddress());
with this line:
serviceIntent.putExtra(TransferService.EXTRAS_GROUP_OWNER_ADDRESS, "192.168.49.1");
As the group owner's IP is always the same, one can write it down directly. As doing so can stop working if the IP changes, I would recommend looking for the group owner's IP instead. The link above show's how to do it.

After establishing TCP connection with server, why can't I see message sent from server?

I have made an app that should connect to a sensor via WiFi Direct, then connect to port 5001 on the sensor to get the sensor data.
I have used "Simple Socket Tester" to start a server on another phone to see if my app succeeded in connecting to port 5001 on that server. When connected, I can send messages to the server, which is displayed on the other phone. But when I send messages to the client from the other phone, I am not receiving the message in my app.
Why is that? Am I missing something inside my code?
public class TCPClient {
public static final String SERVER_IP = "192.168.1.52"; //your computer IP address
public static final int SERVER_PORT = 5001;
// message to send to the server
private String mServerMessage;
// sends message received notifications
private OnMessageReceived mMessageListener = null;
// while this is true, the server will continue running
private boolean mRun = false;
// used to send messages
private PrintWriter mBufferOut;
// used to read messages from the server
private BufferedReader mBufferIn;
/**
* Constructor of the class. OnMessagedReceived listens for the messages received from server
*/
public TCPClient(OnMessageReceived listener) {
mMessageListener = listener;
}
/**
* Sends the message entered by client to the server
*
* #param message text entered by client
*/
public void sendMessage(String message) {
if (mBufferOut != null && !mBufferOut.checkError()) {
mBufferOut.println(message);
mBufferOut.flush();
}
}
/**
* Close the connection and release the members
*/
public void stopClient() {
// send mesage that we are closing the connection
/*sendMessage(Constants.CLOSED_CONNECTION+"Kazy");*/
mRun = false;
if (mBufferOut != null) {
mBufferOut.flush();
mBufferOut.close();
}
mMessageListener = null;
mBufferIn = null;
mBufferOut = null;
mServerMessage = null;
}
public void run() {
mRun = true;
try {
//here you must put your computer's IP address.
InetAddress serverAddr = InetAddress.getByName(SERVER_IP);
Log.e("TCP Client", "C: Connecting...");
//create a socket to make the connection with the server
Socket socket = new Socket(serverAddr, SERVER_PORT);
try {
//sends the message to the server
mBufferOut = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);
//receives the message which the server sends back
mBufferIn = new BufferedReader(new InputStreamReader(socket.getInputStream()));
// send login name
sendMessage("hi");
//in this while the client listens for the messages sent by the server
while (mRun) {
mServerMessage = mBufferIn.readLine();
if (mServerMessage != null && mMessageListener != null) {
//call the method messageReceived from MyActivity class
mMessageListener.messageReceived(mServerMessage);
}
}
Log.e("RESPONSE FROM SERVER", "S: Received Message: '" + mServerMessage + "'");
} catch (Exception e) {
Log.e("TCP", "S: Error", e);
} finally {
//the socket must be closed. It is not possible to reconnect to this socket
// after it is closed, which means a new socket instance has to be created.
socket.close();
}
} catch (Exception e) {
Log.e("TCP", "C: Error", e);
}
}
//Declare the interface. The method messageReceived(String message) will must be implemented in the MyActivity
//class at on asynckTask doInBackground
public interface OnMessageReceived {
public void messageReceived(String message);
}
}
The class where my ConnectTask class is.
public class DeviceDetailFragment extends Fragment implements ConnectionInfoListener {
protected static final int CHOOSE_FILE_RESULT_CODE = 20;
private View mContentView = null;
private WifiP2pDevice device;
private WifiP2pInfo info;
ProgressDialog progressDialog = null;
TCPClient mTCPClient;
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
mContentView = inflater.inflate(R.layout.device_detail, null);
mContentView.findViewById(R.id.btn_connect).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
WifiP2pConfig config = new WifiP2pConfig();
config.deviceAddress = device.deviceAddress;
config.wps.setup = WpsInfo.PBC;
if (progressDialog != null && progressDialog.isShowing()) {
progressDialog.dismiss();
}
progressDialog = ProgressDialog.show(getActivity(), "Press back to cancel",
"Connecting to :" + device.deviceAddress, true, true
// new DialogInterface.OnCancelListener() {
//
// #Override
// public void onCancel(DialogInterface dialog) {
// ((DeviceActionListener)
getActivity()).cancelDisconnect();
// }
// }
);
((DeviceListFragment.DeviceActionListener) getActivity()).connect(config);
}
});
mContentView.findViewById(R.id.btn_disconnect).setOnClickListener(
new View.OnClickListener() {
#Override
public void onClick(View v) {
((DeviceListFragment.DeviceActionListener) getActivity()).disconnect();
}
});
/*
mContentView.findViewById(R.id.btn_start_client).setOnClickListener(
new View.OnClickListener() {
#Override
public void onClick(View v) {
// Allow user to pick an image from Gallery or other
// registered apps
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.setType("image/*");
startActivityForResult(intent, CHOOSE_FILE_RESULT_CODE);
}
});
*/
return mContentView;
}
#Override
public void onConnectionInfoAvailable(final WifiP2pInfo info) {
if (progressDialog != null && progressDialog.isShowing()) {
progressDialog.dismiss();
}
this.info = info;
this.getView().setVisibility(View.VISIBLE);
// The owner IP is now known.
TextView view = (TextView) mContentView.findViewById(R.id.group_owner);
view.setText(getResources().getString(R.string.group_owner_text)
+ ((info.isGroupOwner == true) ? getResources().getString(R.string.yes)
: getResources().getString(R.string.no)));
// InetAddress from WifiP2pInfo struct.
view = (TextView) mContentView.findViewById(R.id.device_info);
view.setText("Group Owner IP - " + info.groupOwnerAddress.getHostAddress());
if(info.groupFormed) {
new ConnectTask().execute("");
if (mTCPClient != null) {
mTCPClient.sendMessage("testing");
}
//sends the message to the server
}
// After the group negotiation, we assign the group owner as the file
// server. The file server is single threaded, single connection server
// socket.
/*
if (info.groupFormed && info.isGroupOwner) {
new FileServerAsyncTask(getActivity(), mContentView.findViewById(R.id.status_text))
.execute();
}
*/
// hide the connect button
mContentView.findViewById(R.id.btn_connect).setVisibility(View.GONE);
}
/**
* Updates the UI with device data
*
* #param device the device to be displayed
*/
public void showDetails(WifiP2pDevice device) {
this.device = device;
this.getView().setVisibility(View.VISIBLE);
TextView view = (TextView) mContentView.findViewById(R.id.device_address);
view.setText(device.deviceAddress);
view = (TextView) mContentView.findViewById(R.id.device_info);
view.setText(device.toString());
}
/**
* Clears the UI fields after a disconnect or direct mode disable operation.
*/
public void resetViews() {
mContentView.findViewById(R.id.btn_connect).setVisibility(View.VISIBLE);
TextView view = (TextView) mContentView.findViewById(R.id.device_address);
view.setText(R.string.empty);
view = (TextView) mContentView.findViewById(R.id.device_info);
view.setText(R.string.empty);
view = (TextView) mContentView.findViewById(R.id.group_owner);
view.setText(R.string.empty);
/*
view = (TextView) mContentView.findViewById(R.id.status_text);
view.setText(R.string.empty);
this.getView().setVisibility(View.GONE);
*/
}
public class ConnectTask extends AsyncTask<String, String, TCPClient> {
#Override
protected TCPClient doInBackground(String... message) {
//we create a TCPClient object
mTCPClient = new TCPClient(new TCPClient.OnMessageReceived() {
#Override
//here the messageReceived method is implemented
public void messageReceived(String message) {
//this method calls the onProgressUpdate
publishProgress(message);
}
});
mTCPClient.run();
return null;
}
#Override
protected void onProgressUpdate(String... values) {
super.onProgressUpdate(values);
//response received from server
Log.d("test", "response " + values[0]);
//process server response here....
}
}
}

Multiple client server android

I'm doing a desktop server application in java with multiple android clients, each one with a thread. I'm using sockets to provide the communication.
Until now, clients are sending messages to the server and then do something based on server response.
But now I need that server send a message to a specific client and I don't know how.
Could you help me please?
Thanks
Server class
import java.net.*;
import java.io.*;
public class Server {
public static void main(String[] args) throws IOException{
boolean listening = true;
try (ServerSocket serverSocket = new ServerSocket(4444)){
while(listening){
new ServerThread(serverSocket.accept()).start();
}
} catch (IOException e) {
System.out.println("Could not listen on port: 4444");
System.exit(-1);
}
}
}
ServerThread
import java.net.*;
import java.io.*;
public class ServerThread extends Thread {
private Socket socket = null;
public ServerThread(Socket socket) {
super("ServerThread");
this.socket = socket;
}
public void run() {
try (
PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
BufferedReader in = new BufferedReader(
new InputStreamReader(
socket.getInputStream()));
) {
String inputLine, outputLine;
GameProtocol gp = new GameProtocol();
outputLine = gp.processInput(null);
//System.out.println(outputLine);
//out.println(outputLine);
while ((inputLine = in.readLine()) != null) {
//System.out.println(outputLine);
outputLine = gp.processInput(inputLine);
System.out.println(outputLine);
out.println(outputLine);
if (outputLine.equals("Bye"))
break;
}
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
TcpClient class
import android.util.Log;
import java.io.*;
import java.net.*;
/**
* Created by andrecorreia on 03/06/16.
*/
public class TcpClient {
public static final String SERVER_IP = "10.0.2.2"; // computer IP address
public static final int SERVER_PORT = 4444;
// message to send to the server
private String mServerMessage;
// sends message received notifications
private OnMessageReceived mMessageListener = null;
// while this is true, the server will continue running
private boolean mRun = false;
// used to send messages
private PrintWriter mBufferOut;
// used to read messages from the server
private BufferedReader mBufferIn;
/**
* Constructor of the class. OnMessagedReceived listens for the messages received from server
*/
public TcpClient(OnMessageReceived listener) {
mMessageListener = listener;
}
/**
* Sends the message entered by client to the server
*
* #param message text entered by client
*/
public void sendMessage(String message) {
if (mBufferOut != null && !mBufferOut.checkError()) {
mBufferOut.println(message);
mBufferOut.flush();
}
}
/**
* Close the connection and release the members
*/
public void stopClient() {
Log.i("Debug", "stopClient");
// send mesage that we are closing the connection
//sendMessage(Constants.CLOSED_CONNECTION + "Kazy");
mRun = false;
if (mBufferOut != null) {
mBufferOut.flush();
mBufferOut.close();
}
mMessageListener = null;
mBufferIn = null;
mBufferOut = null;
mServerMessage = null;
}
public void run() {
mRun = true;
try {
//here you must put your computer's IP address.
InetAddress serverAddr = InetAddress.getByName(SERVER_IP);
//InetAddress serverAddr = InetAddress.getLocalHost();
Log.e("TCP Client", "C: Connecting...");
//create a socket to make the connection with the server
Socket socket = new Socket("192.168.1.92", SERVER_PORT);
try {
Log.i("Debug", "inside try catch");
//sends the message to the server
mBufferOut = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);
//receives the message which the server sends back
mBufferIn = new BufferedReader(new InputStreamReader(socket.getInputStream()));
// send login name
//sendMessage(Constants.LOGIN_NAME + PreferencesManager.getInstance().getUserName());
//sendMessage("Hi");
//in this while the client listens for the messages sent by the server
while (mRun) {
mServerMessage = mBufferIn.readLine();
if (mServerMessage != null && mMessageListener != null) {
//call the method messageReceived from MyActivity class
mMessageListener.messageReceived(mServerMessage);
}
}
Log.e("RESPONSE FROM SERVER", "S: Received Message: '" + mServerMessage + "'");
} catch (Exception e) {
Log.e("TCP", "S: Error", e);
} finally {
//the socket must be closed. It is not possible to reconnect to this socket
// after it is closed, which means a new socket instance has to be created.
socket.close();
}
} catch (Exception e) {
Log.e("TCP", "C: Error", e);
}
}
//Declare the interface. The method messageReceived(String message) will must be implemented in the MyActivity
//class at on asynckTask doInBackground
public interface OnMessageReceived {
public void messageReceived(String message);
}
}
Main Activity
import android.app.Activity;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
public class MainActivity extends Activity implements OnClickListener {
public static TcpClient tcpClient;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new ConnectTask().execute("");
// Set up click listeners for all the buttons
View playNowButton = findViewById(R.id.playNow_button);
playNowButton.setOnClickListener(this);
View optionsButton = findViewById(R.id.options_button);
optionsButton.setOnClickListener(this);
View helpButton = findViewById(R.id.help_button);
helpButton.setOnClickListener(this);
View exitButton = findViewById(R.id.exit_button);
exitButton.setOnClickListener(this);
//---------------------------------------------
}
#Override
public void onClick(View v) {
Intent i;
switch (v.getId()){
case R.id.playNow_button:
i = new Intent(this, PlayNowActivity.class);
startActivity(i);
break;
case R.id.options_button:
i = new Intent(this, OptionsActivity.class);
tcpClient.sendMessage("options");
startActivity(i);
break;
case R.id.help_button:
i = new Intent(this, HelpActivity.class);
tcpClient.sendMessage("help");
startActivity(i);
break;
case R.id.exit_button:
finish();
break;
}
}
public class ConnectTask extends AsyncTask<String,String,TcpClient> {
#Override
protected TcpClient doInBackground(String... message) {
//we create a TCPClient object and
tcpClient = new TcpClient(new TcpClient.OnMessageReceived() {
#Override
//here the messageReceived method is implemented
public void messageReceived(String message) {
//this method calls the onProgressUpdate
publishProgress(message);
}
});
tcpClient.run();
return null;
}
#Override
protected void onProgressUpdate(String... values) {
super.onProgressUpdate(values);
/*View view = adapter.getChildView(0, 0, false, null, null);
TextView text = (TextView) view.findViewById(R.id.betChildOdd);
child2.get(0).get(0).put("OLD", text.getText().toString());
child2.get(0).get(0).put(CONVERTED_ODDS, values[0].toString());
child2.get(0).get(0).put("CHANGE", "TRUE");
adapter.notifyDataSetChanged();*/
}
}
#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);
}
}

The solution you suggested could be something like this?
Thanks
public class Server {
private static ArrayList<ServerThread> playerList;
private static LinkedBlockingQueue<Object> messages;
private static GameProtocol gp ;
public static void main(String[] args) throws IOException{
playerList = new ArrayList<ServerThread>();
messages = new LinkedBlockingQueue<Object>();
gp = new GameProtocol();
Thread accept = new Thread() {
public void run(){
while(true){
try{
ServerSocket serverSocket = new ServerSocket(4444);
ServerThread player = new ServerThread(serverSocket.accept(), gp);
playerList.add(player);
player.start();
}
catch(IOException e){ e.printStackTrace(); }
}
}
};
accept.setDaemon(true);
accept.start();
Thread messageHandling = new Thread() {
public void run(){
while(true){
try{
Object message = messages.take();
// Do some handling here...
System.out.println("Message Received: " + message);
}
catch(InterruptedException e){ }
}
}
};
messageHandling.setDaemon(true);
messageHandling.start();
}
}

Android - Passing simple string over Wi-fi?

I have Wi-fi direct demo. In that we can transfer any image files to other devices. When another device get connected and it shows to send image from gallery. And at other side it shows sent image. But I want to send a simple string and at other side I want to toast that string. Here I am posting a code in which they have implemented file transfer. I am very confused in this code. I am not getting where to change to pass only string. Please help me. Thanks.
DeviceDetailFragment.java
/**
* A fragment that manages a particular peer and allows interaction with device
* i.e. setting up network connection and transferring data.
*/
public class DeviceDetailFragment extends Fragment implements ConnectionInfoListener {
protected static final int CHOOSE_FILE_RESULT_CODE = 20;
private View mContentView = null;
private WifiP2pDevice device;
private WifiP2pInfo info;
ProgressDialog progressDialog = null;
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
mContentView = inflater.inflate(R.layout.device_detail, null);
mContentView.findViewById(R.id.btn_connect).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
WifiP2pConfig config = new WifiP2pConfig();
config.deviceAddress = device.deviceAddress;
config.wps.setup = WpsInfo.PBC;
if (progressDialog != null && progressDialog.isShowing()) {
progressDialog.dismiss();
}
progressDialog = ProgressDialog.show(getActivity(), "Press back to cancel",
"Connecting to :" + device.deviceAddress, true, true
// new DialogInterface.OnCancelListener() {
//
// #Override
// public void onCancel(DialogInterface dialog) {
// ((DeviceActionListener) getActivity()).cancelDisconnect();
// }
// }
);
((DeviceActionListener) getActivity()).connect(config);
}
});
mContentView.findViewById(R.id.btn_disconnect).setOnClickListener(
new View.OnClickListener() {
#Override
public void onClick(View v) {
((DeviceActionListener) getActivity()).disconnect();
}
});
mContentView.findViewById(R.id.btn_start_client).setOnClickListener(
new View.OnClickListener() {
#Override
public void onClick(View v) {
// Allow user to pick an image from Gallery or other
// registered apps
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.setType("image/*");
startActivityForResult(intent, CHOOSE_FILE_RESULT_CODE);
}
});
return mContentView;
}
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
// User has picked an image. Transfer it to group owner i.e peer using
// FileTransferService.
Uri uri = data.getData();
TextView statusText = (TextView) mContentView.findViewById(R.id.status_text);
statusText.setText("Sending: " + uri);
Log.d(WiFiDirectActivity.TAG, "Intent----------- " + uri);
Intent serviceIntent = new Intent(getActivity(), FileTransferService.class);
serviceIntent.setAction(FileTransferService.ACTION_SEND_FILE);
serviceIntent.putExtra(FileTransferService.EXTRAS_FILE_PATH, uri.toString());
serviceIntent.putExtra(FileTransferService.EXTRAS_GROUP_OWNER_ADDRESS,
info.groupOwnerAddress.getHostAddress());
serviceIntent.putExtra(FileTransferService.EXTRAS_GROUP_OWNER_PORT, 8988);
getActivity().startService(serviceIntent);
}
#Override
public void onConnectionInfoAvailable(final WifiP2pInfo info) {
if (progressDialog != null && progressDialog.isShowing()) {
progressDialog.dismiss();
}
this.info = info;
this.getView().setVisibility(View.VISIBLE);
// The owner IP is now known.
TextView view = (TextView) mContentView.findViewById(R.id.group_owner);
view.setText(getResources().getString(R.string.group_owner_text)
+ ((info.isGroupOwner == true) ? getResources().getString(R.string.yes)
: getResources().getString(R.string.no)));
// InetAddress from WifiP2pInfo struct.
view = (TextView) mContentView.findViewById(R.id.device_info);
view.setText("Group Owner IP - " + info.groupOwnerAddress.getHostAddress());
// After the group negotiation, we assign the group owner as the file
// server. The file server is single threaded, single connection server
// socket.
if (info.groupFormed && info.isGroupOwner) {
new FileServerAsyncTask(getActivity(), mContentView.findViewById(R.id.status_text))
.execute();
} else if (info.groupFormed) {
// The other device acts as the client. In this case, we enable the
// get file button.
mContentView.findViewById(R.id.btn_start_client).setVisibility(View.VISIBLE);
((TextView) mContentView.findViewById(R.id.status_text)).setText(getResources()
.getString(R.string.client_text));
}
// hide the connect button
mContentView.findViewById(R.id.btn_connect).setVisibility(View.GONE);
}
/**
* Updates the UI with device data
*
* #param device the device to be displayed
*/
public void showDetails(WifiP2pDevice device) {
this.device = device;
this.getView().setVisibility(View.VISIBLE);
TextView view = (TextView) mContentView.findViewById(R.id.device_address);
view.setText(device.deviceAddress);
view = (TextView) mContentView.findViewById(R.id.device_info);
view.setText(device.toString());
}
/**
* Clears the UI fields after a disconnect or direct mode disable operation.
*/
public void resetViews() {
mContentView.findViewById(R.id.btn_connect).setVisibility(View.VISIBLE);
TextView view = (TextView) mContentView.findViewById(R.id.device_address);
view.setText(R.string.empty);
view = (TextView) mContentView.findViewById(R.id.device_info);
view.setText(R.string.empty);
view = (TextView) mContentView.findViewById(R.id.group_owner);
view.setText(R.string.empty);
view = (TextView) mContentView.findViewById(R.id.status_text);
view.setText(R.string.empty);
mContentView.findViewById(R.id.btn_start_client).setVisibility(View.GONE);
this.getView().setVisibility(View.GONE);
}
/**
* A simple server socket that accepts connection and writes some data on
* the stream.
*/
public static class FileServerAsyncTask extends AsyncTask<Void, Void, String> {
private Context context;
private TextView statusText;
/**
* #param context
* #param statusText
*/
public FileServerAsyncTask(Context context, View statusText) {
this.context = context;
this.statusText = (TextView) statusText;
}
#Override
protected String doInBackground(Void... params) {
try {
ServerSocket serverSocket = new ServerSocket(8988);
Log.d(WiFiDirectActivity.TAG, "Server: Socket opened");
Socket client = serverSocket.accept();
Log.d(WiFiDirectActivity.TAG, "Server: connection done");
final File f = new File(Environment.getExternalStorageDirectory() + "/"
+ context.getPackageName() + "/wifip2pshared-" + System.currentTimeMillis()
+ ".jpg");
File dirs = new File(f.getParent());
if (!dirs.exists())
dirs.mkdirs();
f.createNewFile();
Log.d(WiFiDirectActivity.TAG, "server: copying files " + f.toString());
InputStream inputstream = client.getInputStream();
copyFile(inputstream, new FileOutputStream(f));
serverSocket.close();
return f.getAbsolutePath();
} catch (IOException e) {
Log.e(WiFiDirectActivity.TAG, e.getMessage());
return null;
}
}
/*
* (non-Javadoc)
* #see android.os.AsyncTask#onPostExecute(java.lang.Object)
*/
#Override
protected void onPostExecute(String result) {
if (result != null) {
statusText.setText("File copied - " + result);
Intent intent = new Intent();
intent.setAction(android.content.Intent.ACTION_VIEW);
intent.setDataAndType(Uri.parse("file://" + result), "image/*");
context.startActivity(intent);
}
}
/*
* (non-Javadoc)
* #see android.os.AsyncTask#onPreExecute()
*/
#Override
protected void onPreExecute() {
statusText.setText("Opening a server socket");
}
}
public static boolean copyFile(InputStream inputStream, OutputStream out) {
byte buf[] = new byte[1024];
int len;
long startTime=System.currentTimeMillis();
try {
while ((len = inputStream.read(buf)) != -1) {
out.write(buf, 0, len);
}
out.close();
inputStream.close();
long endTime=System.currentTimeMillis()-startTime;
Log.v("","Time taken to transfer all bytes is : "+endTime);
} catch (IOException e) {
Log.d(WiFiDirectActivity.TAG, e.toString());
return false;
}
return true;
}
}
FileTransferService.java
/**
* A service that process each file transfer request i.e Intent by opening a
* socket connection with the WiFi Direct Group Owner and writing the file
*/
public class FileTransferService extends IntentService {
private static final int SOCKET_TIMEOUT = 5000;
public static final String ACTION_SEND_FILE = "com.example.android.wifidirect.SEND_FILE";
public static final String EXTRAS_FILE_PATH = "file_url";
public static final String EXTRAS_GROUP_OWNER_ADDRESS = "go_host";
public static final String EXTRAS_GROUP_OWNER_PORT = "go_port";
public FileTransferService(String name) {
super(name);
}
public FileTransferService() {
super("FileTransferService");
}
/*
* (non-Javadoc)
* #see android.app.IntentService#onHandleIntent(android.content.Intent)
*/
#Override
protected void onHandleIntent(Intent intent) {
Context context = getApplicationContext();
if (intent.getAction().equals(ACTION_SEND_FILE)) {
String fileUri = intent.getExtras().getString(EXTRAS_FILE_PATH);
String host = intent.getExtras().getString(EXTRAS_GROUP_OWNER_ADDRESS);
Socket socket = new Socket();
int port = intent.getExtras().getInt(EXTRAS_GROUP_OWNER_PORT);
try {
Log.d(WiFiDirectActivity.TAG, "Opening client socket - ");
socket.bind(null);
socket.connect((new InetSocketAddress(host, port)), SOCKET_TIMEOUT);
Log.d(WiFiDirectActivity.TAG, "Client socket - " + socket.isConnected());
OutputStream stream = socket.getOutputStream();
ContentResolver cr = context.getContentResolver();
InputStream is = null;
try {
is = cr.openInputStream(Uri.parse(fileUri));
} catch (FileNotFoundException e) {
Log.d(WiFiDirectActivity.TAG, e.toString());
}
DeviceDetailFragment.copyFile(is, stream);
Log.d(WiFiDirectActivity.TAG, "Client: Data written");
} catch (IOException e) {
Log.e(WiFiDirectActivity.TAG, e.getMessage());
} finally {
if (socket != null) {
if (socket.isConnected()) {
try {
socket.close();
} catch (IOException e) {
// Give up
e.printStackTrace();
}
}
}
}
}
}
}

You can do something like this:
DeviceDetailFragment.java
#Override
protected String doInBackground(Void... params) {
ServerSocket serverSocket = null;
Socket client = null;
DataInputStream inputstream = null;
try {
serverSocket = new ServerSocket(8988);
client = serverSocket.accept();
inputstream = new DataInputStream(client.getInputStream());
String str = inputstream.readUTF();
serverSocket.close();
return str;
} catch (IOException e) {
Log.e(WiFiDirectActivity.TAG, e.getMessage());
return null;
}finally{
if(inputstream != null){
try{
inputstream.close();
} catch (IOException e) {
Log.e(WiFiDirectActivity.TAG, e.getMessage());
}
}
if(client != null){
try{
client.close();
} catch (IOException e) {
Log.e(WiFiDirectActivity.TAG, e.getMessage());
}
}
if(serverSocket != null){
try{
serverSocket.close();
} catch (IOException e) {
Log.e(WiFiDirectActivity.TAG, e.getMessage());
}
}
}
}
#Override
protected void onPostExecute(String result) {
if (result != null) {
Toast.makeText(..., result, ...).show();;
}
}
FileTransferService.java
#Override
protected void onHandleIntent(Intent intent) {
Context context = getApplicationContext();
if (intent.getAction().equals(ACTION_SEND_FILE)) {
String host = intent.getExtras().getString(EXTRAS_GROUP_OWNER_ADDRESS);
Socket socket = new Socket();
int port = intent.getExtras().getInt(EXTRAS_GROUP_OWNER_PORT);
DataOutputStream stream = null;
try {
socket.connect((new InetSocketAddress(host, port)), SOCKET_TIMEOUT);
stream = new DataOutputStream(socket.getOutputStream());
stream.writeUTF("a string");
} catch (IOException e) {
Log.e(WiFiDirectActivity.TAG, e.getMessage());
} finally {
if (stream != null) {
try {
stream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (socket != null) {
if (socket.isConnected()) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
}

Telnet late server reply

I have very strange problem with telnet communication. When I send a message to server, server will reply every time after next message. Server reply looks like this:
// bad IP transmitters adress message
If I send "first message" server will not reply. After I send "second message" server will reply to the first message. Every time reply from server is one message late.
My communication looks like this:
If I use Telnet application from Google Play Store it works perfect and communication looks like this:
C: first message
S: [// bad IP transmitters adress message 'first message']
C: second message
S: [// bad IP transmitters adress message 'second message']
C: third message
S: [// bad IP transmitters adress message 'third message']
Is there some way how fix it? Thank you so much!
Code:
TCPclass
public class TCPclass {
private boolean mRun = false;
String messageFromServer;
private OnMessageReceived mMessageListener = null;
PrintWriter out;
BufferedReader in;
public TCPclass(OnMessageReceived listener) {
mMessageListener = listener;
}
public void stopClient() {
mRun = false;
}
public void sendMessage(String message) {
if (out != null && !out.checkError()) {
message = message + '\r' + '\n';
out.print(message);
out.flush();
Log.i("Terminal", "Message sent.");
}
}
public void start(String hostname, int port) {
mRun = true;
try {
InetAddress serverAddr = InetAddress.getByName(hostname);
Socket socket = new Socket(serverAddr, port);
try {
out = new PrintWriter(new BufferedWriter(
new OutputStreamWriter(socket.getOutputStream())), true);
// receive the message which the server sends back
in = new BufferedReader(new InputStreamReader(
socket.getInputStream()));
while (mRun) {
do
{
String messageFromServer = in.readLine();
if (messageFromServer != null && mMessageListener != null) {
mMessageListener.messageReceived(messageFromServer); //append message to Text View
}
messageFromServer = null;
} while (in.ready());
}
} catch (Exception e) {
Log.e("Terminal", "S: Error ", e);
} finally {
socket.close();
}
} catch (Exception e) {
Log.e("Terminal", "Establish connection error " + hostname + " "
+ port);
}
}
public interface OnMessageReceived {
public void messageReceived(String message);
}
}
MainActivity class:
public class MainActivity extends Activity {
private TCPclass mTcpClass;
public String hostname = "127.0.0.1";
public int port = 7011;
TextView serverMessage;
private connectTask mTask;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final EditText IPaddress = (EditText) findViewById(R.id.eAddress);
final EditText ePort = (EditText) findViewById(R.id.ePort);
final EditText eMessage = (EditText) findViewById(R.id.eMessage);
serverMessage = (TextView) findViewById(R.id.tOutput);
Button okButton = (Button) findViewById(R.id.bOK); //Connect button
okButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) { // connect
// TODO Auto-generated method stub
hostname = IPaddress.getText().toString();
String strPort = ePort.getText().toString();
try {
port = Integer.parseInt(strPort);
} catch (NumberFormatException e) {
Log.e(strPort, "Error port");
}
mTask = new connectTask();
mTask.execute("");
}
});
Button sendButton = (Button) findViewById(R.id.bSend);
sendButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
String message = eMessage.getText().toString();
serverMessage.append("C: " + message + "\n");
Log.i("Terminal", "Sending message " + message);
if (mTcpClass != null) {
mTcpClass.sendMessage(message);
}
eMessage.setText("");
}
});
}
public class connectTask extends AsyncTask<String, String, TCPclass> {
#Override
protected TCPclass doInBackground(String... message) {
Log.i("Terminal", "doInBackground.");
mTcpClass = new TCPclass(new TCPclass.OnMessageReceived() {
#Override
// here the messageReceived method is implemented
public void messageReceived(String message) {
// this method calls the onProgressUpdate
publishProgress(message);
}
});
mTcpClass.start(hostname, port);
return null;
}
#Override
protected void onProgressUpdate(String... values) {
super.onProgressUpdate(values);
serverMessage.append("S: " + Arrays.toString(values) + "\n");
}
}

It seems to me that the server is probably sending a blank or extra line somewhere that you haven't accounted for. I'm the world's last and least fan of calling available() or ready() but maybe this is a case for it:
do
{
String response = in.readLine();
// ...
} while (in.ready());
... at least for debugging purposes, until you sort out exactly what the response is to each line you send. Note that using a while loop here would be definitely incorrect.