Develop Reference

Android WiFi Direct client socket timeout

I'm new to Android, somewhat new to socket programming. I have two devices, running Android 5.1, connected with WiFi direct (not sure if that's relevant). I have a service where the server listens for a request on a socket, then returns a reply back to the client.
Likewise the client code sends a request and listens for the reply from the server. The server is sending the response, but the client never gets the message and the socket times out.
Server test code:
while (true) {
try {
Log.i(TAG, "test waiting for a request");
mServer = new ServerSocket(PORT);
Socket socket = mServer.accept(); //Block to receive message //
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
Log.i(TAG, "Message received! " + in.readLine());
String msg = "This is my reply.";
OutputStream outputStream = socket.getOutputStream();
PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);
out.println(msg);
out.flush();
out.close();
} catch (SocketException e) {
Log.e(TAG, "Socket Accept Interrupted", e);
} catch (IOException e) {
Log.e(TAG, "Socket Failure", e);
} finally {
if (mServer != null && mServer.isBound()) {
try {
mServer.close();
} catch (IOException ioException) {
Log.e(TAG, "Failed to close socket trying to recover from SocketException", ioException);
}
}
}
}
Client test code:
Socket socket = null;
SocketAddress addr = new InetSocketAddress(host, PORT);
int socketTOms = 5000;
try {
socket = new Socket(host, PORT);
socket.setKeepAlive(false);
String syncReq = "Request to server.";
//Send Request//
OutputStream outputStream = socket.getOutputStream();
outputStream.write(syncReq.getBytes());
socket.setSoTimeout(socketTOms);
//Rcv reply//
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
Log.i(TAG, "Message received! " + in.readLine());
} catch (SocketTimeoutException e) {
Log.e(TAG, "Timeout while reading from socket: timeout=" + socketTOms);
} catch (Exception e) {
Log.e(TAG, "Exception", e);
} finally {
if (socket != null && socket.isConnected()) {
try {
socket.close();
} catch (IOException e) {
Log.e(TAG, "Exception while closing socket", e);
}
}
}
I'm running the server and client on two different devices through Android Studio and can see in the logs that the server receives the request and sends the reply, but the client always throws SocketTimeoutException. I saw else where that socket.setKeepAlive(false) would fix the problem, but it doesn't seem to have any effect.
Seems simple enough, but I can't see what I'm missing here.

May be try this line of code before infinite loop mServer = new ServerSocket(PORT);
Did you try to create thread in sever side app. This makes the process to run in parallel so that while server is waiting for request the application does not gets hang. First of all try this code for localhost . To find Inetaddress just use InetAddress.getLocalHost(). Then run this. For communication with different devices there is service provided that is called (NSD) (Network Service Discovary).
But if you want to run this way I have written a code for you.
Server side code
TextView textView;
Button button;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView=(TextView)findViewById(R.id.textView);
button=(Button)findViewById(R.id.button);
button.setOnClickListener(
new View.OnClickListener() {
#Override
public void onClick(View v) {
connect();
}
}
);
}
public void connect()
{
MyServer myServer= new MyServer();
myServer.setEventListener(this);
myServer.startListening();
}
#Override
public void Display(String message) {
textView.setText("Client - "+ message);
}
}
Client side code
TextView textView;
Button button;
Thread mThread;
Socket clientSocket;
Button sendBtn;
public String userText1;
ObjectOutputStream output;
EditText editText;
Object userText;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView=(TextView)findViewById(R.id.textView);
button=(Button)findViewById(R.id.button);
sendBtn=(Button)findViewById(R.id.sendBtn);
editText=(EditText)findViewById(R.id.editText);
sendBtn.setOnClickListener(
new View.OnClickListener() {
#Override
public void onClick(View v) {
userText=editText.getText().toString();
start();
}
}
);
public void start()
{
mThread= new Thread(new Runnable() {
#Override
public void run() {
try {
clientSocket = new Socket("127.0.0.1", 2001);
Log.v("binaya", "client socket created");
output = new ObjectOutputStream(clientSocket.getOutputStream());
output.writeObject(userText);
Message serverObj = Message.obtain();
ObjectInputStream input = new ObjectInputStream(clientSocket.getInputStream());
String strMsg = input.readObject().toString();
serverObj.obj = strMsg;
mHandler.sendMessage(serverObj);
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
});
mThread.start();
}
Handler mHandler= new Handler()
{
#Override
public void handleMessage(Message msg) {
msgDisplay(msg.obj.toString());
}
};
private void msgDisplay(String msg) {
textView.setText("Server - " + msg);
}
We have used handler because we cannot touch user interface from inside runnable in this case.
Thanks

Figured this out ....
On the client side I was using outputStream.write(...) to send the request to the server as in:
String syncReq = "Request to server.";
OutputStream outputStream = socket.getOutputStream();
outputStream.write(syncReq.getBytes());
But reading it on the server with BufferedReader.readLine():
Socket socket = mServer.accept(); //Block to receive message //
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
Log.i(TAG, "Message received! " + in.readLine());
My problem was that outputStream.write(...) does not append a '\n' at the end of the String, but in.readLine() on the server expects it. Therefore the server was blocking while waiting for '\n'; which in turn caused the client socket to timeout.

Getting socket timeout when receiving frequent requests at once

I attempting to build a remote controller for my laptop using my phone.
I written a server application that running on my laptop, the remote app used as a client to the server application.
I want to implement a mouse pad, the problem is when I am moving my finger over the "touch pad" too fast, I am receiving read time out on server side after few iterations.
Server code
final ExecutorService clientProcessingPool = Executors.newFixedThreadPool(20);
Runnable serverTask = new Runnable()
{
#Override
public void run()
{
ServerSocket serverSocket = null;
try
{
serverSocket = new ServerSocket(DEFAULT_PORT);
serverSocket.setReuseAddress(true);
_working = true;
while (_working)
{
Socket clientSocket = serverSocket.accept();
clientSocket.setSoTimeout(10000);
clientProcessingPool.submit(new ClientTask(clientSocket));
}
}
catch (IOException e)
{
System.err.println("Unable to process client request");
e.printStackTrace();
}
finally
{
try
{
if (serverSocket != null)
{
serverSocket.close();
}
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
};
Thread serverThread = new Thread(serverTask);
serverThread.start();
private class ClientTask implements Runnable
{
private final Socket clientSocket;
private ClientTask(Socket clientSocket)
{
this.clientSocket = clientSocket;
}
#Override
public void run()
{
System.out.println("Got a client !");
try
{
System.out.println("Connected!");
DataOutputStream dOut = new DataOutputStream(clientSocket.getOutputStream());
DataInputStream dIn = new DataInputStream(clientSocket.getInputStream());
String request = dIn.readUTF();
parseRequest(request);
System.out.println("request=" + request);
dOut.writeUTF("Got the command");
dOut.flush(); // Send off the data
dIn.close();
dOut.close();
clientSocket.close();
}
catch (Exception e)
{
e.printStackTrace();
}
}
I thought maybe I will send the requests only if the distance from the starting position to end position is bigger than STEPS(a constant) and only then send the request. But I think the mouse won`t move fluidly.
Thanks.

RXAndroid and RXJava are perfect for asynchronously handling these request and will allow you to add a debounce to the frequent requests. Check out Reactive.io

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

Android proxy using sockets

I'm trying to create a proxy in Android and I have to use sockets . I've read many tutorials and came up with following code. Unfortunately browser doesn't seem to get any data and after some time it displays standard web page saying that web page is not available. What might be the cause? Thanks for your help.
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(9902, 0, InetAddress.getByName("localhost"));
} catch (Exception e) {
e.printStackTrace();
}
if (serverSocket != null) {
while (!Thread.currentThread().isInterrupted()) {
try {
Socket socket = serverSocket.accept();
new Thread(new RunnableToReadSocketData(socket)).start();
} catch (Exception e) {
e.printStackTrace();
}
}
}
private class RunnableToReadSocketData implements Runnable {
private final Socket clientSocket;
public RunnableToReadSocketData(Socket socket) {
this.clientSocket = socket;
}
#Override
public void run() {
Socket serverSocket = null;
try {
InputStream streamFromClient = clientSocket.getInputStream();
PrintWriter streamToClient = new PrintWriter(clientSocket.getOutputStream());
StringWriter writer = new StringWriter();
IOUtils.copy(streamFromClient, writer);
String requestString = writer.toString();
int firstSpace = requestString.indexOf(" ");
int secondSpace = requestString.indexOf(" ", ++firstSpace);
String url = requestString.substring(firstSpace, secondSpace);
Uri uri = Uri.parse(url);
String urlWithoutProtocol = uri.getHost();
System.out.println("==============Reading Socket==============\n" + clientSocket.toString() + "\n" + requestString);
serverSocket = new Socket(urlWithoutProtocol, 80);
PrintWriter streamToServer = new PrintWriter(serverSocket.getOutputStream(), true);
streamToServer.write(requestString);
streamToServer.flush();
InputStream streamFromServer = serverSocket.getInputStream();
StringWriter writerResponse = new StringWriter();
IOUtils.copy(streamFromServer, writerResponse);
String responseString = writerResponse.toString();
System.out.println("==============RECEIVED==============\n" + serverSocket.toString() + "\n" + responseString);
streamToClient.write(responseString);
streamToClient.flush();
streamToClient.close();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (serverSocket != null) {
serverSocket.close();
}
if (clientSocket != null) {
clientSocket.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}

You're doing this wrong. After you process the CONNECT command you need to start two threads to copy bytes over the connection, one in each direction. Don't attempt to read the entire request before you send anything; ditto the response. Just copy bytes as you receive them.
When you read EOS on one socket, shutdown the other socket for output and exit that thread. If you've already shutdown the socket you read the EOS from, close both and exit the thread. You need this in case either end does a shutdown, to propagate it properly.

I agree with previous.
The general principle is:
Client connects
Start reading thread
Receive request
Parse destination
Open socket to destination
Forward request
For every Read on the destination socket, do a write on the client socket
For every Read on client socket, do a write on destination socket
If either socket closes (errors), close the other
So, two InputStream's, two OutputStreams, and just ferry data across them.

ServerSocket Android

Hey community I have the following ServerSocket which should listen to port 53000 and log any received data. However, I cannot seem to get past the server.accept() blocking call.
public void run() {
SocketServer server = new ServerSocket(53000);
//---buffer store for the stream---
byte[] buffer = new byte[1024];
//---bytes returned from read()---
int bytes;
//---keep listening to the InputStream until an
// exception occurs---
while (true) {
try {
socket = server.accept();
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String str = in.readLine();
Log.i("received response from server", str);
in.close();
socket.close();
} catch (IOException e) {
Log.e(TAG, e.getMessage());
} catch (Exception e){
server.close();
Log.e(TAG, e.getMessage());
}
}
}
I have also given the application the INTERNET permission in the Manifest file.
()
To add to the mystery, I have also verified client responses get sent to that port.
Is there something in particular I need to do to make this work?
Thanks.

Your code is very messy and won't even compile. I made some adjustments so that i could test your code, and it's working fine. Here is the test application I used:
package com.test.stackoverflow
import java.io.BufferedReader;
public class ServerSocketTestActivity extends Activity {
/** Called when the activity is first created. */
private static String TAG = "ServerSocketTest";
private ServerSocket server;
Runnable conn = new Runnable() {
public void run() {
try {
server = new ServerSocket(53000);
while (true) {
Socket socket = server.accept();
BufferedReader in = new BufferedReader(
new InputStreamReader(socket.getInputStream()));
String str = in.readLine();
Log.i("received response from server", str);
in.close();
socket.close();
}
} catch (IOException e) {
Log.e(TAG, e.getMessage());
} catch (Exception e) {
Log.e(TAG, e.getMessage());
}
}
};
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
new Thread(conn).start();
}
#Override
protected void onPause() {
super.onPause();
if (server != null) {
try {
server.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
Using this code and netcat running via adb shell I was able to connect and communicate with the application.

When working with The Client Declare these methods
To access Streams
// gets the input stream // ObjectInputStream input;
// gets the output stream // ObjectOutputStream output;
// ServerSocket server;
// Socket connection;
maybe you have a another class to access the socket;
server = new ServerSocket(5001, 100);
// step 1 create socket connection
server = new ServerSocket(5001, 100);
while(the condition is true)
// step 2 wait for connection
// step 3 get streams
// step 4 : process the connection
// step 5 : close connection