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.

TCP Socket connection not working on Android 4.4

Faced a weird problem when TCP connection via Socket is not established on Android 4.4 for some reason. It works fine on 4.1.1 and 5.0.
#Override
protected Void doInBackground(Void... params) {
try {
// Creating InetAddress object from ipNumber passed via constructor from IpGetter class.
InetAddress serverAddress = InetAddress.getByName(host);
// Create a new Socket instance and connect to host
socket = new Socket(serverAddress, port);
Log.i(TAG, "Socket created: " + host + ":" + port);
// Create PrintWriter object for sending messages to server.
out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true); //thread freezes here
//Create BufferedReader object for receiving messages from server.
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
Log.d(TAG, "In/Out created");
} catch (UnknownHostException e) {
Log.e(TAG, "Don't know about host: " + host + ":" + port);
connected = false;
Log.e(TAG, e.getMessage());
} catch (IOException e) {
Log.e(TAG, "Couldn't get I/O for the connection to: " + host + ":" + port);
connected = false;
Log.e(TAG, e.getMessage());
}
connected = true;
return null;
}
For some reason Thread stops on I/O creation.
Any ideas what causes this? Maybe someone seen that problem before?

Communicating android and windows through socket

I want to make my android app open socket to my windows console app and they communicate with each other. The socket is opened and data is sent and received in windows app, but my android app does not receive the answer which sent by windows. I watch the packets in my android and I saw the packets are coming but I do not know why my app do not receive it!
windows app server class:
class Server
{
private TcpListener tcpListener;
private Thread listenThread;
public Server()
{
Console.WriteLine("\nStarting server...");
this.tcpListener = new TcpListener(IPAddress.Any, 1234);
this.listenThread = new Thread(new ThreadStart(ListenForClients));
this.listenThread.Start();
}
private void ListenForClients()
{
Console.WriteLine("\nWaiting for clients to connect...");
this.tcpListener.Start();
while (true)
{
//blocks until a client has connected to the server
TcpClient client = this.tcpListener.AcceptTcpClient();
//create a thread to handle communication with connected client
Thread clientThread = new Thread(new ParameterizedThreadStart(HandleClientComm));
clientThread.Start(client);
}
}
private void HandleClientComm(object client)
{
Console.WriteLine("\nIncoming from client...");
TcpClient tcpClient = (TcpClient)client;
NetworkStream clientStream = tcpClient.GetStream();
byte[] message = new byte[4096];
int bytesRead;
try
{
while (true)
{
bytesRead = 0;
try
{
//blocks until a client sends a message
bytesRead = clientStream.Read(message, 0, 4096);
}
catch
{
//a socket error has occured
break;
}
if (bytesRead == 0)
{
//the client has disconnected from the server
break;
}
//message has successfully been received
ASCIIEncoding encoder = new ASCIIEncoding();
Console.WriteLine("\nReceived: \n\n" + encoder.GetString(message, 0, bytesRead));
//By FMR
string response = "random responsive: " + new Random().Next(1000).ToString() + "\n";//"\r\n";
//writeData(clientStream, response);
byte[] msg = System.Text.Encoding.ASCII.GetBytes(response);
// Send back a response.
clientStream.Write(msg, 0, msg.Length);
clientStream.Flush();
Console.WriteLine("\nResponed ..." + response);
}
}
catch (Exception ex)
{
Console.WriteLine("\nException while: " + ex.Message);
}
tcpClient.Close();
}
}
my android thread:
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
Socket socket = null;
ServerSocket serverSocket = null;
Boolean bRun = true;
try {
socket = new Socket(ip, port);
if(outputStream == null) {
outputStream = new DataOutputStream(socket.getOutputStream());
}
// become server
serverSocket = new ServerSocket(port);
Log.i(G.TAG, "before serverSocket.accept");
socket = serverSocket.accept();
Log.i(G.TAG, "response recieve: ");
inputStream = new BufferedReader(new InputStreamReader(socket.getInputStream()));
}
catch (Exception e) {
try {
serverSocket.close();
} catch (IOException e1) {
Log.e(G.TAG, "serverSocket.close() e: " + e1.getMessage());
}
try {
socket.close();
} catch (IOException e1) {
Log.e(G.TAG, "socket.close() e: " + e1.getMessage());
}
}
Log.i(G.TAG, "after start recieve: ");
while (bRun) {
try {
Log.i(G.TAG, "while start: ");
String message = inputStream.readLine();
Log.i(G.TAG, "response message: " + message);
if (message != null) {
setListMessage(false, message);
}
}
catch (IOException e) {
bRun = false;
Log.e(G.TAG, "while bRun e: " + e.getMessage());
}
}
}
});
thread.start();
// in another function, my message is sent successfully from android and receive in windows

I found the problem, this line
socket = serverSocket.accept();
made the problem when I comment the line, the android app received the response!
Does anybody know why?

how to send message to all connected client from server

i've created an android application in which, android application act as the client, and server resides in the desktop application.
suppose there are 10 android application runs the same at a time on 10 different android tablets, when one updation received from one tablet, the desktop application sends the updation to all other remaining tablets. how could the server knows how many clients are connected and how to send the message to all the clients
what i plan is to run a server in all android so that when one updation received from one tablet, the desktop application sends the updation to all other remaining tablets.
can anyone please tell me some suggestion regarding this.
Client side
private int SERVER_PORT = 9999;
class Client implements Runnable {
private Socket client;
private PrintWriter out;
private Scanner in;
#Override
public void run() {
try {
client = new Socket("localhost", SERVER_PORT);
Log.d("Client", "Connected to server at port " + SERVER_PORT);
out = new PrintWriter(client.getOutputStream());
in = new Scanner(client.getInputStream());
String line;
while ((line = in.nextLine()) != null) {
Log.d("Client", "Server says: " + line);
if (line.equals("Hello client")) {
out.println("Reply");
out.flush();
}
}
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
Server class
class ServerThread implements Runnable {
private ServerSocket server;
#Override
public void run() {
try {
server = new ServerSocket(SERVER_PORT);
Log.d("Server", "Start the server at port " + SERVER_PORT
+ " and waiting for clients...");
while (true) {
Socket socket = server.accept();
Log.d("Server",
"Accept socket connection: "
+ socket.getLocalAddress());
new Thread(new ClientHandler(socket)).start();
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
class ClientHandler implements Runnable {
private Socket clientSocket;
private PrintWriter out;
private Scanner in;
public ClientHandler(Socket clietSocket) {
this.clientSocket = clietSocket;
}
#Override
public void run() {
try {
out = new PrintWriter(clientSocket.getOutputStream());
in = new Scanner(clientSocket.getInputStream());
String line;
Log.d("ClientHandlerThread", "Start communication with : "
+ clientSocket.getLocalAddress());
out.println("Hello client");
out.flush();
while ((line = in.nextLine()) != null) {
Log.d("ClientHandlerThread", "Client says: " + line);
if (line.equals("Reply")){
out.print("Server replies");
out.flush();
}
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

You could save the Sockets in a List and send a message through all the OutputStreams in that List:
Socket socket = Server.accept();
sockets.add(socket); //sockets is an ArrayList<Socket>
public void sendMessageToEveryone(String msg) {
for(Socket s : sockets) {
s.getOutputStream().write(msg.getBytes());
s.getOutputStream().flush();
}

You could use the Google Cloud Messaging service.
Take a look at this page:
https://developer.android.com/google/gcm/index.html

send data from android to a udp port in web server2008

i want to send data(latitude and longitude )to a web server (windows server 2008) who"s ip and udp port is known from my android application .how to do so ?
here is a sample code which i m trying but data is not received to other end
public class UDPServer extends Activity {
WebView view;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState) ;
setContentView(R.layout.main);
view=(WebView) findViewById(R.id.webView1);
try {
String serverHostname = new String ("ip and udp port");
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
DatagramSocket clientSocket = new DatagramSocket();
InetAddress IPAddress = InetAddress.getByName(serverHostname);
System.out.println ("Attemping to connect to " + IPAddress +
") via UDP port 7777");
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
System.out.print("Enter Message: ");
String sentence = inFromUser.readLine();
sendData = sentence.getBytes();
Log.i("send","send");
System.out.println ("Sending data to " + sendData.length +
" bytes to server.");
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress,7777);
clientSocket.send(sendPacket);
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
System.out.println ("Waiting for return packet");
clientSocket.setSoTimeout(10000);
try {
clientSocket.receive(receivePacket);
String modifiedSentence =
new String(receivePacket.getData());
InetAddress returnIPAddress = receivePacket.getAddress();
int port = receivePacket.getPort();
System.out.println ("From server at: " + returnIPAddress +
":" + port);
System.out.println("Message: " + modifiedSentence);
}
catch (SocketTimeoutException ste)
{
System.out.println ("Timeout Occurred: Packet assumed lost");
}
clientSocket.close();
}
catch (UnknownHostException ex) {
System.err.println(ex);
}
catch (IOException ex) {
System.err.println(ex);
}
}

In UDP, unlike TCP, there is no connection established. Every UDP packet travels on it's own.
My guess is that you can send a UDP packet to server, but you do not receive the return packet. The reason for this is NAT which is used on all home routers and cellular networks. NAT prevents delivery of inbound (internet to device) packets.
To test this assumption, try this with device and server on the same local network.