I build a TCP multicast chat application using asynctask.
I am also trying to order the message in FIFO and causal order.
However, when I try to send a lot of messages simultaneously for testing, it misses some messages but I can't find the reason.
I have tried as hard as I can to improve the performance of the program because I thought the performance could be the reason. but still having the same issue.
I attached some important part of my code.
Most of all,
private class ServerTask extends AsyncTask<ServerSocket, String, Void> {
#Override
protected Void doInBackground(ServerSocket... sockets){
ServerSocket serverSocket = sockets[0];
Socket socket = new Socket();
try {
while(true) {
socket = serverSocket.accept();
InputStream inputstream = socket.getInputStream();
DataInputStream in = new DataInputStream(new BufferedInputStream(inputstream));
String msg = ""+in.readUTF();
String time = ""+in.readUTF();
String temp = time+"||"+msg;
publishProgress(temp);
in.close();
}} catch (IOException e) {
e.printStackTrace();
} finally{
try {
socket.close();
serverSocket.close();////
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
Here is onProgressUpdate.
protected void onProgressUpdate(String...strings) {
/*
* The following code displays what is received in doInBackground().
*/
String strReceived = strings[0].trim();
TextView remoteTextView = (TextView) findViewById(R.id.textView1);
remoteTextView.append(strReceived + "\t\n");
try {
sequencer(strReceived);
} catch (ParseException e) {
e.printStackTrace();
}
return;
}
}
..
private class ClientTask extends AsyncTask<String, Void, Void> {
#Override
protected Void doInBackground(String... msgs) {
Date currentDate= new Date();
Timestamp time = new Timestamp(currentDate.getTime());
Message temp = new Message(myPort, msgs[0], time);////
try {
for(int i = 0; i <= 2; i++) {
Socket socket = new Socket();
socket.connect(new InetSocketAddress(InetAddress.getByAddress(new byte[]{10, 0, 2, 2}),
Integer.parseInt(REMOTE_PORTS[i])), 1000);
socket.setTcpNoDelay(true);
OutputStream outputStream = socket.getOutputStream();
DataOutputStream o = new DataOutputStream(new BufferedOutputStream(outputStream));
o.writeUTF(msgs[0]);
o.writeUTF(""+time);
o.flush();////
socket.close();
}
}
catch (UnknownHostException e) {
Log.e(TAG, "ClientTask UnknownHostException");
} catch (IOException e) {
Log.e(TAG, "ClientTask socket IOException");
}
return null;
}
Can you find the part causes the problem?
Sequencing / Queueing /Acknowledgement all these things are part of TCP so it is done by the protocol itself so you do not need to do all those explicitly from your code. There are still some parts of your code that can be improved. Like:
String time = received.split("\\|\\|")[0];
String msgToSend = received.split("\\|\\|")[1];
//Instead of doing this, its better to do this:
String peices[]=received.split("\\|\\|");
String msgToSend=peices[1];
String time=peices[0]
Also you can check if you are receiving all the raw messages and if its during the parsing process the messages are getting lost using a log:
Log.d("RAW_MESSAGE","Message Received: "+temp); //in your doInBackground
If you get all the messages that you send in this log, then there is nothing wrong with the protocol or the sending/receiving process rather there is a problem while you are processing the message. Also for these types of use-cases, try using the Service component rather than AsyncTask.
I hope this helps.
First of all multicast is over UDP, not TCP.
And if you want to create a multicast app, you should use multicastsocket
http://developer.android.com/reference/java/net/MulticastSocket.html
Related
I am using Android app to communicate, send and receive messages through TCP socket with a PC java application on the same LAN. Below is the code of Asynctask i am using in android to send a message and receive a reply from PC:
public class Client extends AsyncTask<Void, Void, Void> {
Context context;
String dstAddress;
int dstPort;
String msg;
Client(Context context, String addr, int port, String msg) {
this.context = context;
dstAddress = addr;
dstPort = port;
this.msg = msg;
}
String reply = "";
#Override
protected Void doInBackground(Void... arg0) {
Socket socket = null;
try {
socket = new Socket(dstAddress, dstPort);
BufferedWriter dout = new BufferedWriter( new OutputStreamWriter( socket.getOutputStream() ));
BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
//send request
dout.write(msg);
dout.flush();
dout.close();
//get response
reply = br.readLine();
br.close();
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return null;
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// DISPLAY REPLY CONTENT
Handler handler = new Handler(context.getMainLooper());
handler.post( new Runnable(){
public void run(){
Toast.makeText(context, "Server reply: " + reply ,Toast.LENGTH_LONG).show();
}
});
}
}
I am displaying the reply of the PC in a toast in onPostExcecute.
Android sends the message through BufferedWriter, while the java app on PC receives it in a BufferedReader. (working fine, and tested)
The PC sends a response throught a BufferedWriter to the android after receiving the message, where the android receives the reply in a BufferedReader as shown: br.readLine(). (HERE is the problem): According to the PC's app debug the reply is sent successfully without any IOExceptions or errors happening, But at the android side the reply string is empty, looks like it received nothing. I really don't know what am I doing wrong, and hope someone can point out to what i am missing.
Below is the server's thread that handles a client socket, the thread runs basically whenever serversocket accepts a socket:
static class clientThread extends Thread {
Socket s = null;
clientThread(Socket s) //constructor
{
this.s = s;
}
#Override
public void run ()
{
try
{
BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream())); //receiving data into a buffered reader
String dataIn = br.readLine(); // reading the buffered data into a string
System.out.println("received: " + dataIn);
//BufferedWriter dout = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
//dout.write("OK");
//dout.newLine();
PrintWriter dout = new PrintWriter(new BufferedWriter(new OutputStreamWriter(s.getOutputStream())), true);
if(dataIn.equals("Android client"))
{
dout.println("OK");
dout.flush();
System.out.println("OK sent");
}
dout.close();
br.close();
s.close();
}
catch (IOException e)
{ System.out.println("Error occured"); }
}
}
SO to sum up the programs, the android sends the message "Android client" (Which the server receives and prints on the console with no issues), now with the reply, the server sends "OK" with no issues as well, but android side receives nothing.
ALSO, as i mentioned before, if i remove
dout.close();
from android's asynctask after i send the message, the server receives the message ONLY when the program gets terminated, I dont understand why i have to close it in order for the message to be sent successfully.
You are reading lines but you aren't sending lines. Add a line terminator to the message sent by the client, or use BufferedWriter.newLine(); and flush() instead of closing the buffered writer.
I have an app that connects to a RaspberryPi via Bluetooth and loops the same data to it while it receives some data back.
I had some issues with the connection so this workaround is needed to connect my android phone to the RaspberryPi: IOException: read failed, socket might be closed - Bluetooth on Android 4.3
For some reason, the android phone is receiving its own output.
The String "Hello Raspberry. It's me, AndroidPhone" is sent to the output in a never-ending loop. The incoming data (from the RaspberryPi) is also read in a never-ending loop.
But somehow I don't only receive the data from the RaspberryPi but also the string sends via smartphone. This is my code:
public class MainActivity extends AppCompatActivity {
private BluetoothAdapter bluetoothAdapter;
UUID SERIAL_UUID = UUID.fromString("00001101-0000-1000-8000-00805f9b34fb");
#Override
protected void onCreate(Bundle savedInstanceState) {
// (...)
// Only GUI-stuff until this point
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
BluetoothDevice raspberryPi = bluetoothAdapter.getRemoteDevice("B8:27:EB:56:DC:B2");
BluetoothSocket btSocket;
try {
btSocket = raspberryPi.createRfcommSocketToServiceRecord(SERIAL_UUID);
btSocket.connect();
} catch (IOException e) {
Log.e("BTError", e.getMessage());
// Workaround, found on: https://stackoverflow.com/questions/18657427/ioexception-read-failed-socket-might-closed-bluetooth-on-android-4-3
try {
Log.e("BTError", "Trying fallback...");
btSocket = (BluetoothSocket) raspberryPi.getClass().getMethod("createRfcommSocket", new Class[]{int.class}).invoke(raspberryPi, 1);
btSocket.connect();
(new Thread(new SendingThread(btSocket))).start();
(new Thread(new ReceivingThread(btSocket))).start();
} catch (Exception e2) {
Log.e("BTError", e2.getMessage());
Log.e("BTError", "Couldn't establish Bluetooth connection!");
}
}
}
private class SendingThread extends Thread {
private OutputStream out;
public SendingThread(BluetoothSocket btSocket) {
try {
out = btSocket.getOutputStream();
} catch (IOException e) {
e.printStackTrace();
}
}
#Override
public void run() {
try {
int delay = 100000000;
while (true) {
if (delay == 0) {
Log.i("WRT", "Written to RaspberryPi");
out.write("Hello Raspberry. It's me, AndroidPhone".getBytes());
delay = 100000000;
}
delay--;
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
private class ReceivingThread extends Thread {
private InputStream in;
public ReceivingThread(BluetoothSocket btSocket) {
try {
in = btSocket.getInputStream();
} catch (IOException e) {
e.printStackTrace();
}
}
#Override
public void run() {
int data = 0;
while (true) {
try {
data = in.read();
} catch (IOException e) {
e.printStackTrace();
}
Log.i("RCV", String.valueOf((char) data));
}
}
}
On the RaspberryPi end, everything looks normal. A simple java program starts the Linux command rfcomm listen /dev/rfcomm0 and reads from/writes to the file /dev/rfcomm0 with FileReader and FileWriter. The only relevant lines on this end are:
run {
// Inside writer-thread
bluetoothWriter = new BufferedWriter(new FileWriter("/dev/rfcomm0"));
while(true) {
bluetoothWriter.write("This is RaspPi");
bluetoothWriter.flush();
}
}
and
run {
// Inside reader-thread
bluetoothReader = new BufferedReader(new FileReader("/dev/rfcomm0"));
while(true) {
int incData = bluetoothReader.read();
System.out.print((char) incData);
}
}
Thank you for your help!
edit: Still no solution to this problem. I suspected that the RaspberryPi is somehow sending back what it received. But when I disabled that it sends out anything, the smartphone still directly receives what it has sent out.
I scoured over the Bluetooth classes sources. The workaround seems legit from the first glances. Try this first:
if (delay == 0) {
Log.i("WRT", "Written to RaspberryPi");
out.write("Hello Raspberry. It's me, AndroidPhone".getBytes());
out.flush(); // <-- You are not flushing
delay = 100000000;
}
And the message sticks in you socket for you to read over and over again.
If that does not fix it the other option I can think of is that somehow the socket is initialized to be a socket to your Android device. The .createRfcommSocket() method seems to create a socket to your own device if the Bluetooth device is null when the socket was being created. I'm not sure how this would exactly happen, but if the Raspberry Pi's state is somehow mangled after exception I suppose it could be something to look into.
On the raspy side: If you are just starting both of those threads doesn't it mean that you are constantly sending messages to /dev/rfcomm0 and flushing. I recommend that you change it so that raspy reacts to a received message by sending back the wanted message instead of spamming all the time. I'm not sure if this is part of your problem but it would at least make debugging & development a bit easier.
I am not sure if this is the solution you need, because I don't know if you are using bluetooth classic or bluetooth 4.0>+, but I wrote a library for text based BLE and WiFi P2P 2-way communication for android (and I know the Raspberry Pi is capable of BLE communication), I don't create a socket connection for BLE communication though, but I do for WiFi P2P. Take a look, I hope it helps. It isn't published yet, so you would have to clone/fork the repo.
I think you have trouble writing
As far as I know, for buffer, should use \n and ...
bluetoothWriter.write("This is RaspPi\n");
But I prefer to use a combination of DataOutputStream and BufferedReader
For Read:
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
try {
String line = bufferedReader.readLine();
System.out.println(line);
} catch (IOException e) {
e.printStackTrace();
}
for write:
DataOutputStream dataOutputStream = new DataOutputStream(outputStream);
String s = "Hi\n";
try {
dataOutputStream.write(s.getBytes());
} catch (IOException e) {
e.printStackTrace();
}
It is better to correct the point made by a dear friend about flush() ...
I'm not sure, please test yourself ...
I'm having an issue with a messaging app I'm working on and was hoping someone could point me in the right direction. I'm stuck on getting the client and server to communicate properly.
My client multicasts a message to 5 processes, which make their alterations on the server side and send them back to the client. This all works fine, however when I try to multicast a second time, the server is getting stuck reading and eventually gives me the error: W/System.err (with no other information) at the line I point out in the code.
Client code:
private class ClientTask extends AsyncTask<String, Void, Void> {
#Override
protected Void doInBackground(String... msgs) {
try{
String msg = msgs[0];
int ID = Integer.parseInt(msgs[1]);
ObjectOutputStream out;
clock++;
Message m1 = new Message(clock, msg, ID);
for (int i = 0; i < 5; ++i) {
String remotePort = REMOTE_PORT[i];
Socket socket = new Socket(InetAddress.getByAddress(new byte[]{10, 0, 2, 2}),
Integer.parseInt(remotePort));
out = new ObjectOutputStream(socket.getOutputStream());
out.writeObject(m1);
out.flush();
ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
Message m2 = (Message)in.readObject();
proposed_seq_from_q = m2.seq_number;
all_proposed.add(proposed_seq_from_q);
socket.close();
}
agreed_deliver = Collections.max(all_proposed);
m1.set_seq_number(agreed_deliver);
for (int i = 0; i < 5; ++i) {
String remotePort = REMOTE_PORT[i];
Socket socket = new Socket(InetAddress.getByAddress(new byte[]{10, 0, 2, 2}),
Integer.parseInt(remotePort));
out = new ObjectOutputStream(socket.getOutputStream());
out.writeObject(m1);
out.flush();
socket.close();
}
} catch(ClassNotFoundException e){
Log.e(TAG, "ClientTask: ClassNotFoundException");
e.printStackTrace();
} catch (UnknownHostException e) {
Log.e(TAG, "ClientTask: UnknownHostException");
e.printStackTrace();
} catch (IOException e) {
Log.e(TAG, "ClientTask: IOException");
e.printStackTrace();
}
return null;
}
}
Server code:
private class ServerTask extends AsyncTask<ServerSocket, String, Void> {
#Override
protected Void doInBackground(ServerSocket... sockets) {
ServerSocket serverSocket = sockets[0];
boolean listening = true;
try{
while(listening) {
Socket clientSocket = serverSocket.accept();
ObjectInputStream in = new ObjectInputStream(clientSocket.getInputStream());
Message m = (Message)in.readObject();
new_proposed = Math.max(new_proposed + 1, clock);
m.set_seq_number(new_proposed);
ObjectOutputStream out = new ObjectOutputStream(clientSocket.getOutputStream());
out.writeObject(m);
holdback_queue.add(m);
// ******************************************************
// THIS IS WHERE IT IS CRASHING
// ******************************************************
m = (Message)in.readObject();
publishProgress(m.get_message());
}
}catch(Exception e){
Log.e(TAG, "FAIL");
e.printStackTrace();
}
return null;
}
I've tried everything I can think of but I'm unable to get the server to read the second message. Everything is working up and being passed through with no issues up until that exact point. Can anyone please tell me what I'm doing wrong?
I'm trying to send a single string from android to pc and after a bit of research on this site and others I've found out about sockets and how to use them. I have written the server program that can receive strings sent to it. Below is the code.
//static ServerSocket variable
private static ServerSocket server;
//socket server port on which it will listen
private static int port = 9021;
public static void main(String [] args) throws IOException, ClassNotFoundException{
server = new ServerSocket(port);
while(true){
System.out.println("Waiting for client request." + InetAddress.getLocalHost());
Socket socket = server.accept();
ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
String message = (String)ois.readObject();
System.out.println("Message received: " + message);
ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
oos.writeObject("Hi Client: " + message);
ois.close();
oos.close();
socket.close();
if(message.equalsIgnoreCase("exit")){
break;
}
}
System.out.println("Shutting down serve");
server.close();
}
I have tested this using a pc client program that sends string and have confirmed that this server script works. I am trying to now implement the same concept in android but facing a lot of trouble mostly due to the fact that the tutorials online for this task is very outdated (2-3 years) so nothing works as expected. Can anyone tell me how to write a very simple android app in which a single string is sent over socket?
From what I can see in the logcat, the outdated tutorials on the internet are not working because android has apparently introduced in recent versions a very aggressive process manager which monitors the behaviour of threads and if there is any repeated thread actions, it shuts it down without notice.
Edit: As per a solution I have implemented an asynctask. But now the server is not receiving and says Address already in use. I think it is because of socket address in my android code. Please help!
public class MainActivity extends Activity {
private Button button;
private EditText message;
private TextView finalResult;
//InetAddress host;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
message = (EditText) findViewById(R.id.et_time);
button = (Button) findViewById(R.id.btn_do_it);
finalResult = (TextView) findViewById(R.id.tv_result);
/*
try {
host = InetAddress.getLocalHost();
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}*/
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View arg0) {
AsyncTaskRunner runner = new AsyncTaskRunner();
String msg = message.getText().toString();
runner.execute(msg);
}
});
}
private class AsyncTaskRunner extends AsyncTask<String, String, String> {
Socket socket = null;
ObjectOutputStream oos = null;
ObjectInputStream ois = null;
int clientport = 8080;
String resp;
#Override
protected String doInBackground(String... params) {
publishProgress("Sending...");
String msg = params[0];
for(int i=0;i<=5;i++){
//establish socket connection to server
try {
socket = new Socket( "100.69.73.16",clientport);
//write to socket using Objectouputstream
oos = new ObjectOutputStream(socket.getOutputStream());
oos.writeObject(msg+i);
oos.close();
socket.close();
Thread.sleep(100);
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
resp = "Message has been sent";
return resp;
}
#Override
protected void onPostExecute(String result) {
finalResult.setText(result);
}
#Override
protected void onPreExecute() {
}
#Override
protected void onProgressUpdate(String... values) {
finalResult.setText(values[0]);
}
}
}
Ok so I solved the problem of 'address already used' by changing port number. Apparently the port number was being used by other programs on my laptop. So in retrospect for anyone checking on how to do this, you can use my above code and remember to change the port number in both codes to something similar. Also in my android code where the socket is opened, you can put in the local ip address (very important, google gives you external) for your computer.
I'm programming a network software with Java, but I have a real problem using my application through a "true" network.
Let a software be a host, and listening for client connexions.
Here is my Server loop :
public void run() {
while (mServerSocket != null) {
try {
Socket wClient = mServerSocket.accept();
System.out.println("Client connecté");
wClient.setSoTimeout(50);
wClient.setTcpNoDelay(false);
Client c = new Client(wClient);
synchronized(this) {
mWaitingClients.add(c);
c.start();
}
} catch(Exception ex) {
System.out.println("Server error : " + ex.getMessage());
}
}
}
When a client tried to connect to the server, I use this function :
public Client connect(InetAddress addr, int port) throws Exception {
Socket socket = new Socket(addr, port);
socket.setSoTimeout(50);
socket.setTcpNoDelay(false);
Client c = new Client(socket);
c.start();
return c;
}
And here is the client loop :
public void run() {
try {
ObjectOutputStream out = new ObjectOutputStream(mSocket.getOutputStream());
ObjectInputStream in = new ObjectInputStream(mSocket.getInputStream());
while(mSocket.isConnected() && !mSocket.isClosed()) {
for (int i = 0; i < mOutMessages.size(); i++) {
Message msg = mOutMessages.get(i);
out.writeObject(msg);
}
out.flush();
mOutMessages.clear();
Thread.sleep(50);
out.reset();
while(true) {
try {
Message m = (Message) in.readObject();
mInMessages.add(m);
} catch (Exception e) {
break;
}
}
Thread.sleep(50);
}
} catch(Exception ex) {
try {
mSocket.close();
} catch(Exception exx) {
exx.printStackTrace();
}
ex.printStackTrace();
}
}
Some other parts of the program do Message and put them in the Output list of the Client (mOutMessages).
Some other parts of the program read Message from the mInMessages of the Client.
But something is wrong with this. It works fine locally (server and client on the same computer), but fail or is hazardous (some messages are sent but never received) using two computers (with LAN or through the Internet).
Server ever detect connexions from the clients, send "handshake" messages to the client, but the client never receives them.
I'm more a C programmer than a Java one, and I never had this kind of problem using libc Sockets, so, why my way of doing is wrong ?
Thank you !
Edit :
My Server is created using this function :
public void open(int port) throws Exception {
mServerSocket = new ServerSocket(port);
start(); // Call the run mentionned above.
}
Edit :
Here is my solution, maybe it's not perfect but it works !
public void run() {
try {
BufferedOutputStream buf_out = new BufferedOutputStream(
mSocket.getOutputStream()
);
BufferedInputStream buf_in = new BufferedInputStream(
mSocket.getInputStream()
);
ObjectOutputStream out = new ObjectOutputStream(buf_out);
out.flush();
ObjectInputStream in = new ObjectInputStream(buf_in);
while(mSocket.isConnected() && !mSocket.isClosed()) {
for (int i = 0; i < mOutMessages.size(); i++) {
Message msg = mOutMessages.get(i);
out.writeObject(msg);
out.flush();
}
mOutMessages.clear();
out.reset();
while(true) {
try {
Message m = (Message) in.readObject();
mInMessages.add(m);
} catch (Exception e) {
break;
}
}
}
} catch(Exception ex) {
try {
mSocket.close();
} catch(Exception exx) {
exx.printStackTrace();
}
ex.printStackTrace();
}
If I understand right, both client and server use the run method. If both client and server happen to write sufficiently large messages (not fitting in involved buffers) at the same time then you get a deadlock because neither partner advances to reading (which would drain full buffers). Due to network delays, this might only happen in the non-local scenario, i.e. there may be enough time to pile up enough messages in the mOutMessages buffer.
Note that documentation of Socket.setSoTimeout (which you used) only says that it affects read()s. (For example, in my JDK, ObjectOutputStream seems to use a BlockDataOutputStream with a buffer size of 1024 bytes).
I recommend to either use a separate thread for reading/writing or (if you know the maximum messages size) use a sufficiently large buffer (by wrapping the SocketOutputStream in a BufferedOutputStream). If you opt for larger buffers, you may also want to write one message at a time (and try to read messages after each).