Develop Reference

UDP Sending via android cannot be automatic

I can send udp and received udp, the problem that I had face now is when i need to automatic sending data from client to server(to prove that the client is alive), the the server cannot received the data. but when I send the alive status via Button event. it worked.
here's my code
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
establishConnection();
/* Working */
Button send = new Button(this);
send.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
new Thread(new Runnable() {
#Override
public void run() {
DatagramPacket receivePacket = null;
byte[] command = (room+":Alive").getBytes();
try {
receivePacket = new DatagramPacket(command, command.length, InetAddress.getByName(UrlColletion.hostAddress), 8084);
} catch (UnknownHostException e) {
e.printStackTrace();
}
java.lang.System.out.println("Sending");
try {
serverSocket1.send(receivePacket);
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}
});
/* Not Working*/
final Handler handler = new Handler(Looper.getMainLooper());
Runnable runnable = new Runnable() {
#Override
public void run() {
try {
DatagramPacket receivePacket = null;
byte[] command = (room + ":Alive").getBytes();
try {
receivePacket = new DatagramPacket(command, command.length, InetAddress.getByName(UrlColletion.hostAddress), 8084);
} catch (UnknownHostException e) {
e.printStackTrace();
}
java.lang.System.out.println("Sending");
try {
serverSocket1.send(receivePacket);
} catch (IOException e) {
e.printStackTrace();
}
} catch (Exception e) {
// TODO: handle exception
} finally {
//also call the same runnable to call it at regular interval
handler.postDelayed(this, 5000);
}
}
};
handler.post(runnable);
setContentView(send);
}
DatagramSocket serverSocket1;
void establishConnection(){
try {
serverSocket1 = new DatagramSocket(7070);
serverSocket1.setReuseAddress(true);
} catch (SocketException e) {
e.printStackTrace();
}
new Thread(new Runnable() {
#Override
public void run() {
boolean isOpen = true;
while(isOpen) {
byte []message = new byte[1024];
DatagramPacket receivePacket = new DatagramPacket(message, 1024);
try {
serverSocket1.receive(receivePacket);
} catch (IOException e) {
e.printStackTrace();
}
String text = new String(message, 0, receivePacket.getLength());
System.out.println(text);
}
serverSocket1.close();
}
}).start();
}
the code above is tested. when it send via handler, the server cannot received any data, while button, it can.
Additional information, the code is working on emulator, but when it comes on phone, the problem comes out. so it means on emulator the udp is sending successfully, but on phone, no.

Try to disable battery optimization or maybe implement a wakelock.
https://developer.android.com/training/scheduling/wakelock
Intent intent = new Intent();
intent.setAction(Settings.ACTION_IGNORE_BATTERY_OPTIMIZATION_SETTINGS);
startActivity(intent);

Don't know why but i just an thread on that.
final Handler handler = new Handler(Looper.getMainLooper());
Runnable runnable = new Runnable() {
#Override
public void run() {
try {
new Thread(new Runnable() {
#Override
public void run() {
DatagramPacket receivePacket = null;
byte[] command = (room + ":Alive").getBytes();
try {
receivePacket = new DatagramPacket(command, command.length, InetAddress.getByName(UrlColletion.hostAddress), 8084);
} catch (UnknownHostException e) {
e.printStackTrace();
}
java.lang.System.out.println("Sending");
try {
serverSocket1.send(receivePacket);
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
} catch (Exception e) {
// TODO: handle exception
} finally {
//also call the same runnable to call it at regular interval
handler.postDelayed(this, 5000);
}
}
};
handler.post(runnable);

I Cant Put Thread.sleep() in my Class extends Runnable

i Use Socket To communicate between android and wifi its return me OutOfMemory Error When i Trying to disconnect 3 seconds after Sending Data
i have an interface to handle data:
public interface SocketConnections {
public void onSocketConnectionChanged(boolean isConnected, Socket socket);
public void onMessageRecieved(String Message);
public void onMessageSent();
}
SocketClass
public class connectSocket implements Runnable {
public Socket socket;
private DataOutputStream out;
private InputStream in;
private SocketConnections connections;
private static final String TAG = "connectSocket";
public connectSocket(SocketConnections connections) {
this.connections = connections;
}
#Override
public void run() {
connect();
}
private void connect() {
disconnect();
try {
try {
new Thread(new Runnable() {
#Override
public void run() {
try {
Thread.sleep(1000);
socket = new Socket(wsConfig.HOST_ADDRESS, wsConfig.PORT_NUMBER);
socket.setTcpNoDelay(true);
socket.setKeepAlive(true);
if (socket.isConnected()) {
connections.onSocketConnectionChanged(true, socket);
Log.i(TAG, "Connected");
while (socket.isConnected()) {
out = new DataOutputStream(socket.getOutputStream());
in = socket.getInputStream();
String S;
if (in != null) {
while (true) {
byte[] content = new byte[1024];
try {
Thread.sleep(2000);
int bytesRead = in.read(content);
if (bytesRead == -1) {
break;
}
byte[] x = Arrays.copyOfRange(content, 0, bytesRead);
Log.i(TAG, "run: " + x.length);
S = Util.fromByteArrayToHexString(x);
connections.onMessageRecieved(S);
} catch (Exception e) {
}
}
}
}
}
} catch (Exception e) {
connections.onSocketConnectionChanged(false, socket);
e.printStackTrace();
}
}
}).start();
} catch (Exception ignored) {
}
} catch (Exception ignored) {
}
}
public void sendData(final byte[] S) {
Runnable runnable = new Runnable() {
#Override
public void run() {
try {
Thread.sleep(100);
out.write(S);
out.flush();
connections.onMessageSent();
} catch (Exception e) {
e.printStackTrace();
}
}
};
Thread thread = new Thread(runnable);
thread.start();
}
public void disconnect() {
if (socket != null && socket.isConnected()) {
try {
socket.close();
connections.onSocketConnectionChanged(false, socket);
// Toast.makeText(G.context, "سیستم به سرور متصل نیست.", Toast.LENGTH_SHORT).show();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
i want to add 3 seconds delay after sending data and Disconnect
like this
public void sendData(final byte[] S) {
Runnable runnable = new Runnable() {
#Override
public void run() {
try {
Thread.sleep(100);
out.write(S);
out.flush();
connections.onMessageSent();
Thread.sleep(3000);
disconnect();
} catch (Exception e) {
e.printStackTrace();
}
}
};
Thread thread = new Thread(runnable);
thread.start();
}
its return me out of memory error and force close what should i do?

ok so i found my problem and solved it. i'm not sure but i think when i'm trying to sleep thread inside other thread its some how its going to stop itself before start or i don't know whats happens there but when i put sleep in other method and call that in my first thread its works fine. if some one know about it tell us

ServerSocket.accept() doesn't works in second time

I'm beginer in android and i'm trying develop a connection TCP server.
I have this class:
public class JavaTCPServer {
public static void send(String aMessage) {
final String msg = aMessage;
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
Socket socket = null;
try {
ServerSocket serverSocket = GlobalSingleton.getInstance().getServerSocket();
socket = serverSocket.accept();
PrintWriter printWriter = new PrintWriter(socket.getOutputStream(), true);
printWriter.println(msg);
printWriter.flush();
printWriter.close();
} catch (IOException ex) {
ex.printStackTrace();
} finally {
if (socket != null) {
try {
socket.close();
socket = null;
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
}
});
thread.start();
}
}
private ServerSocket serverSocket; //Created in GlobalSingleton Class...
try {
serverSocket = new ServerSocket(Constantes.TCP_PORT);
} catch (IOException e) {
e.printStackTrace();
}
I can send message normally in the first time, but when i try to send message the second time the software remains in line: socket = serverSocket.accept(); and the message in printWriter.println(msg) is not sent.
Additional Information
When i kill the app in settings and open i can send once.
Any questions don't hesitate ask me.
Thanks for all!

Your code only accepts one connection, processes it, and then exits. It does not behave as you have described.
You need a loop.
You also need to start a separate thread to handle each connection.
And calling a method that accepts connections send() is inside out and back to front.

I solved my own problem.
I wrote my class as the follow bellow code:
public class JavaTCPServer {
private ServerSocket serverSocket;
private String message;
private Handler updateConversationHandler;
private Thread serverThread = null;
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
public ServerSocket getServerSocket() {
return serverSocket;
}
public void setServerSocket(ServerSocket serverSocket) {
this.serverSocket = serverSocket;
}
public JavaTCPServer() {
setUpdateConversationHandler(new Handler());
this.serverThread = new Thread(new ServerThread());
this.serverThread.start();
}
public Handler getUpdateConversationHandler() {
return updateConversationHandler;
}
public void setUpdateConversationHandler(Handler updateConversationHandler) {
this.updateConversationHandler = updateConversationHandler;
}
class ServerThread implements Runnable {
public void run() {
Socket socket = null;
try {
serverSocket = new ServerSocket(Constantes.TCP_PORT);
} 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 BufferedReader input;
private String messageSend;
public CommunicationThread(Socket clientSocket) {
this.clientSocket = clientSocket;
try {
this.setInput(new BufferedReader(new InputStreamReader(
this.clientSocket.getInputStream())));
} catch (IOException e) {
e.printStackTrace();
}
}
public void run() {
while (!Thread.currentThread().isInterrupted()) {
Central central = GlobalSingleton.getInstance()
.get_current_central();
if (central != null) {
if ((central.getStep() <= central.getObjetivo()) &&
(central.getStep() == 99)){
try {
messageSend = getMessage();
PrintWriter printWriter = new PrintWriter(
clientSocket.getOutputStream(), true);
printWriter.println(messageSend);
printWriter.flush();
try {
Thread.sleep(1500);
} catch (InterruptedException e) {
e.printStackTrace();
}
printWriter.println(Constantes.EXIT_CONFIG);
printWriter.flush();
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
} catch (IOException e) {
e.printStackTrace();
}
central.setStep(central.getStep() + 1);
}
}
/*
* try { String read = input.readLine();
* updateConversationHandler.post(new updateUIThread(read)); }
* catch (IOException e) { e.printStackTrace(); }
*/
}
}
public BufferedReader getInput() {
return input;
}
public void setInput(BufferedReader input) {
this.input = input;
}
}
}
With this class you can send and receive tcp messages all the time.
Thanks for all help!

Serversocket.accept() function is for accepting a new client and connecting with the client, for messages you need to use DataInputStream() and DataOutputStream() after connecting with the server. This happens because for the first time server accepts the new client and process further but after this it does not get a new connection and it waits for new connection at serversocket.accept().

closing client let the server crash

I've a simple client and server on android. Everything works fine except when I close the client app then the server stops working the app closes.
I think it's about not closing the socket. But when I close the socket in the client the server still stops working.
I'm running a thread on the server. This is my server code:
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 BufferedReader input;
public CommunicationThread(Socket clientSocket) {
this.clientSocket = clientSocket;
try {
this.input = new BufferedReader(new InputStreamReader(this.clientSocket.getInputStream()));
} catch (IOException e) {
e.printStackTrace();
}
}
public void run() {
while (!Thread.currentThread().isInterrupted()) {
try {
String read = input.readLine();
updateConversationHandler.post(new updateUIThread(read));
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
class updateUIThread implements Runnable {
private String msg;
private boolean feedback = false;
public updateUIThread(String str) {
msg = str;
}
#Override
public void run() {
parseCommand();
if(feedback)
{
textFeedback.setText(msg);
feedback = false;
}
else
{
textTv.setText(msg);
}
}

if(msg != null)
parseCommand();
and in
while (!Thread.currentThread().isInterrupted()) {
try {
String read = input.readLine();
if(read == null)
{
clientSocket.close();
Log.d("Test","SOCKET CLOSED");
return;
}
updateConversationHandler.post(new updateUIThread(read));
} catch (IOException e) {
e.printStackTrace();
}
}

How to stop Socket to send a lot of useless data when closed?

I use these codes for communicating between devices. If i close or kill the client app, the server app gets thousands of useless data. The textView in the server side is full of this: Client says: null. If i close the client twice, the server stops with StackOverFlowError. How can i make the code to dont send this null values when the app stops? Or can i filter the server side to do nothing when getting this data?
Client:
public class Client 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.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();
}
}
}
}
Server:
public class Server extends Activity {
private ServerSocket serverSocket;
Handler updateConversationHandler;
Thread serverThread = null;
private TextView text;
public static final int SERVERPORT = 1599;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
text = (TextView) findViewById(R.id.text2);
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 BufferedReader input;
public CommunicationThread(Socket clientSocket) {
this.clientSocket = clientSocket;
try {
this.input = new BufferedReader(new InputStreamReader(this.clientSocket.getInputStream()));
} catch (IOException e) {
e.printStackTrace();
}
}
public void run() {
while (!Thread.currentThread().isInterrupted()) {
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() {
text.setText(text.getText().toString()+"Client Says: "+ msg + "\n");
}
}
}

I think you should use a delimiter character, to tell the Server your Client it's about to die. Add that character of code in onPause method of your Android Activity/Fragment.
Then in your Server, just get the String or byte and compare it against your Delimiter String/Character and stop the Server listening for the Connection.

while (!Thread.currentThread().isInterrupted()) {
try {
String read = input.readLine();
updateConversationHandler.post(new updateUIThread(read));
} catch (IOException e) {
e.printStackTrace();
}
}
The problem is here. You aren't checking the result of readLine() for null. If it returns null, the peer has closed the connection and you should do likewise, and exit this loop. You can probably get rid of the isInterrupted() test as well.
Also, if you get any IOException other that a read timeout when reading from a socket, the connection is dead and you must close the socket and exit your loop.