Develop Reference

Socket Connection Always Null When Connecting To Remote Server

Good day.Im trying to connect to server with socket.Here is my code on how i do it.
private class SocketConnection extends AsyncTask<String, String, String> {
PrintWriter out;
BufferedReader in;
#Override
protected String doInBackground(String... params) {
connect();
try {
out = new PrintWriter(clientSocket.getOutputStream());
in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
} catch (IOException ex) {
System.out.append("error").append("socketcoonection").println();
}
String msg = null;
try {
msg = in.readLine();
} catch (IOException e) {
e.printStackTrace();
}
while (run) {
System.out.append(msg).append("socketcoonection").println();
out.println();
out.flush();
/*try {
msg = in.readLine();
} catch (IOException ex) {
Logger.getLogger(MainActivity.class.getName()).log(Level.SEVERE, null, ex);
}*/
}
return null;
}
}
and here is the connect() method
public void connect() {
try {
clientSocket = new Socket("vaenterprises.org/test.php", 8080);
} catch (UnknownHostException ex) {
} catch (IOException ex) {
}
if (clientSocket != null) {
run = true;
}
}
and this is the server side php code of test.php
echo json_encode("socket working");
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
and the address link is vaenterprises.org/test/php so im trying to connect to it and read the input or output stream or the echo.Whatever i do,i get nullPointerException at System.out.append(msg).append("socketcoonection").println(); and during debug i figured out that its socket which is null...Please tell me what am i doing wrong?

ServerSocket closing itself in AsyncTask [Android Wifi P2P Manager ]

I am developing a android wifi -chat application .
Bit of Info about my app :
->A device calls startserver() to act as a server ,another device calls start client() to act as a client
What works:
->A Client can successfully send the data for the first time to the client, but not again and again
->I need to call startserver() again on first device , so that client can send data again .
The startserver() calls this Async task ,the following is its DoinBackgroundMethod
protected String doInBackground(Void... params) {
ServerSocket serverSocket = null;
try {
while(true) {
serverSocket = new ServerSocket(PORT);
Socket client = serverSocket.accept();
StartMSG(client);
}
} catch (IOException e) {
return null;
} finally {
try {
chatclient.changeserverrunning(false);
if (serverSocket == null) {
} else {
serverSocket.close();
}
return null;
} catch (Exception e) {
}
}
//return null;
}
protected void StartMSG(Socket client){
try {
InputStream inputstream = client.getInputStream();
ObjectInputStream ois = new ObjectInputStream(inputstream);
Message m = null;
try {
m = (Message) ois.readObject();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
if (m != null) {
if (m.gettype() == 1) {
final String my_msg = m.getMessage();//Toast msg afterwards
}
}catch (Exception e){
}
}
Client Side Code :
It is started when the client hits send button and calls start client method .in which It sets up the Ip values before and bundles them and calls the message sending part as a Intent Service called FileTransferService
Its code is (abstracted) :
protected void onHandleIntent(Intent intent) {
Context context = getApplicationContext();
if(socket==null){
socket = new Socket();
}
if (intent.getAction().equals(ACTION_SEND_FILE)) {
final String msg_type=intent.getExtras().getString(MESSAGE_TYPE);
String host = intent.getExtras().getString(EXTRAS_ADDRESS);
int port = intent.getExtras().getInt(EXTRAS_PORT);
try {
socket.bind(null);
socket.connect((new InetSocketAddress(host, port)), SOCKET_TIMEOUT);
Message m = (Message) intent.getExtras().getSerializable(MESSAGE_INTENT_STR);
final String my_message=m.getMessage();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(baos);
oos.writeObject(m);
oos.flush();
oos.close();
InputStream is = new ByteArrayInputStream(baos.toByteArray());
OutputStream stream = socket.getOutputStream();
ChatClient.copyFile(is, stream);
} catch (IOException e) {
} finally {
if (socket != null) {
if (socket.isConnected()) {
try {
//socket.close();
} catch (Exception e) {
// Give up
e.printStackTrace();
}
}
}
}
}
}

You should try https://github.com/tavendo/AutobahnAndroid and run the client from a service, from an asyntask it will always end up finishing.

Transfer String from android to pc via bluetooth

Since many days i am going through many examples and questions related to my issue but nothing helps!
Aim
two way communication between pc(windows) and android (like passing msg to pc and acknowledgement from pc)
What i have done till now
I am able to send String to pc(windows) from my android device using bluetooth.
here is the code i used
private String sendFile(String mac_address, String device_name) {
// TODO Auto-generated method stub
String result="";
btAdapter = BluetoothAdapter.getDefaultAdapter();
BluetoothDevice device = btAdapter.getRemoteDevice(mac_address);
Log.d("BT_SENDING_FILE",device_name+" "+mac_address);
try {
Method m = device.getClass().getMethod("createRfcommSocket", new Class[] {int.class});
btSocket = (BluetoothSocket) m.invoke(device, 1);
if(!btSocket.isConnected()){
Log.d(" is connected Status",""+btSocket.isConnected());
// device.createInsecureRfcommSocketToServiceRecord(UUID);
}
btAdapter.cancelDiscovery();
try{
btSocket.connect();
}catch(IOException e){
btSocket =(BluetoothSocket) device.getClass().getMethod("createRfcommSocket", new Class[] {int.class}).invoke(device,1);
btSocket.connect();
Log.d("fall back","in catch clause");
}
byte[] msgBuffer = stringToSend.getBytes();
outStream = btSocket.getOutputStream();
outStream.write(msgBuffer);
if (outStream != null) {
outStream.flush();
}
result = "sent";
outStream.close();
btSocket.close();
Log.d("BLUETOOTH","Closing Socket");
} catch (Exception e) {
System.out.println(e);
Log.d("BLUETOOTH","exception while sending through bluetooth");
result = "failed";
e.getLocalizedMessage();
} finally{}
return result;
}
this is running good without any problem.
Problem
But i am not able to receive any String from pc to android device. I have tried many things
I have tried this
BluetoothSocket socket = null;
BluetoothAdapter mAdapter = BluetoothAdapter.getDefaultAdapter();
while (true) {
try {
// Creating a new listening server socket
Log.d("BT", ".....Initializing RFCOMM SERVER....");
mmServerSocket = mAdapter.listenUsingInsecureRfcommWithServiceRecord("Bluetooth", MY_UUID);
// This is a blocking call and will only return on a
// successful connection or an exception
Log.d("Socket","listening...");
socket = mmServerSocket.accept(120000);
} catch (Exception e) {
}
try {
Log.d("Socket", "Closing Server Socket.....");
mmServerSocket.close();
InputStream tmpIn = null;
OutputStream tmpOut = null;
// Get the BluetoothSocket input and output streams
tmpIn = socket.getInputStream();
tmpOut = socket.getOutputStream();
Log.d("BT","IO stream init");
DataInputStream mmInStream = new DataInputStream(tmpIn);
DataOutputStream mmOutStream = new DataOutputStream(tmpOut);
// use the Input Stream to take the string from the client whoever is connecting
//similarly use the output stream to send the data to the client
StringBuilder sb = new StringBuilder();
while((ch = mmInStream.read())!= -1)
sb.append((char)ch);
String res = sb.toString();
Log.d("BT",res);
tv_response.setText(res));
} catch (Exception e) {
//catch your exception here
e.printStackTrace();
Log.d("Exception","some thing went wrong");
e.getLocalizedMessage();
}
}
}
I am using Blue Cove in windows. I HAVE GONE THROUGH BLUETOOTH CHAT SAMPLE PROJECT but dont understand any thing
your help is appreciated
thank you

i tried following code and it was successful. it may help you
BluetoothSocket socket = null;
while (true) {
try {
Log.i(ACCEPT_TAG, "Listening for a connection...");
socket = mServerSocket.accept();
Log.i(ACCEPT_TAG, "Connected to " + socket.getRemoteDevice().getName());
} catch (IOException e) {
break;
}
// If a connection was accepted
if (socket != null) {
// Do work to manage the connection (in a separate thread)
try {
// Read the incoming string.
String buffer;
DataInputStream in = new DataInputStream(socket.getInputStream());
buffer = in.readUTF();
Intent i = new Intent(MESSAGE_RECEIVED_INTENT);
i.putExtra("Message", String.format("%s", buffer));
Log.d("BT response is",buffer);
c.sendBroadcast(i);
} catch (IOException e) {
Log.e(ACCEPT_TAG, "Error obtaining InputStream from socket");
e.printStackTrace();
}
try {
mServerSocket.close();
} catch (IOException e) { }
break;
}
}
Be sure that your device is visible to all i.e scan mode is BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE
else use this code
public void requestBTDiscoverable() {
Intent i = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
i.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);
startActivityForResult(i, REQ);
int result = 0;
this.onActivityResult(REQ, result, i);
Log.i(TAG, "Bluetooth discoverability enabled");
}

Android socket connect freezing

I am trying to implement a simple socket that sends and receives strings from a server.
The following code is freezing the application, not sure if I have done something obviously wrong?
public String internetRoutesRetrieve(String userName) {
String command = null;
String response = null;
Socket socket = null;
DataOutputStream dataOutputStream = null;
DataInputStream dataInputStream = null;
try {
socket = new Socket("Hidden IP", HiddenPort);
dataOutputStream = new DataOutputStream(socket.getOutputStream());
dataInputStream = new DataInputStream(socket.getInputStream());
command = "SEARCH <" + userName + ">";
dataOutputStream.writeUTF(command);
response = dataInputStream.readUTF();
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
finally {
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (dataOutputStream != null) {
try {
dataOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (dataInputStream != null) {
try {
dataInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return response;
}
Thanks
Edit: It seems the program is freezing when I am trying to save the response from the server

see AsyncTask for proper client server communication on Android application.
you'd usualy get android.os.NetworkOnMainThreadException if you don't but I'd give it a try.

Transfer data between 2 android devices

I'd like write an app to transfer data between 2 android devices on the same wifi network, like as there is a share folder.
How can i do this?
Thanks
EDIT (My solution):
My Server wait for request
private boolean startServer() {
try {
server = new ServerSocket(port);
} catch (IOException ex) {
ex.printStackTrace();
return false;
}
return true;
}
public void runServer() {
while (this.go) {
try {
Log.d("BurgerClub", "Server in attesa di richieste");
Socket s1 = server.accept();
OutputStream s1out = s1.getOutputStream();
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(
s1out));
BufferedReader br = new BufferedReader(new FileReader(this.path));
String counter = br.readLine();
counter = counter != null ? counter : "000";
br.close();
bw.write(counter);
bw.close();
s1.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
My Client (Runnable object)
public void run() {
try {
this.openConnection();
// Se il socket è connesso
if( !this.s1.isClosed() ) {
InputStream is = this.s1.getInputStream();
BufferedReader dis = new BufferedReader(new InputStreamReader(is));
line = dis.readLine();
if( !this.previousCounter.equals(line.trim()) ) {
((BurgerClub_MonitorActivity) counterContext).runOnUiThread(new Runnable() {
#Override
public void run() {
TextView edit = (TextView)(((BurgerClub_MonitorActivity) counterContext).findViewById(R.id.textActionCounter));
edit.setText(line);
}
});
this.previousCounter = line.trim();
}
dis.close();
}
} catch (ConnectException connExc) {
connExc.printStackTrace();
} catch (IOException ex) {
ex.printStackTrace();
} catch (Throwable ex) {
ex.printStackTrace();
}

One device needs to serve as a server and the other one will be the client.
The basic flow needs to be something of this sort:
Server device opens a socket and listens on it.
Server device broadcasts the local IP and port it's listening on.
Client device receives broadcast and initiates a connection.
Perform data transfer.

Read about NFC (Near field communication)
http://developer.android.com/guide/topics/connectivity/nfc/index.html