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Can't send objects using Sockets

Hello Im writing an app in which client sends name of room to server, server creates it and then sends back whole list of rooms. I have problem with receiving this object from server also whats interesting when I close clients' app and open again I have list of rooms just like it should be. I refresh room list in client app but its always empty only reopening helps that's pretty weird and I don't know an issue of this.
On client side:
getIs() method is returning is object
getOs() method returning os object
this.os = new ObjectOutputStream(clientSocket.getOutputStream());
this.is = new ObjectInputStream(clientSocket.getInputStream());
private void createRoom(ActionEvent event) {
String roomName = "CreateRoom ";
roomName += setRoomName();
String response = null;
try {
client.getOs().writeObject(roomName);
response = (String) client.getIs().readObject();
System.out.println(response);
} catch (IOException | ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private void refreshRooms() {
String response = null;
try {
client.getOs().writeObject("RefreshRooms");
response = (String) client.getIs().readObject();
System.out.println(response);
rooms = (Rooms) client.getIs().readObject();
System.out.println("Print in client: ");
rooms.printAllRooms();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Server:
this.os = new ObjectOutputStream(connection.getOutputStream());
this.is = new ObjectInputStream(connection.getInputStream());
public void run() {
String inputRequest = null;
try {
while((inputRequest = (String) ois.readObject()) != null) {
System.out.println(inputRequest);
handleRequest(inputRequest);
}
} catch (IOException | ClassNotFoundException e) {
System.out.println("Client has disconnected.");
e.printStackTrace();
}
}
private void handleRequest(String request) {
String response = null;
String[] msg = request.split(" ");
if(msg[0].equals("CreateRoom")) {
try {
oos.writeObject("You want create a room.");
Room newRoom = new Room(msg[1]);
rooms.addRoom(newRoom);
System.out.println("Created room: " + newRoom.getName());
System.out.println("\n Print after creation: ");
rooms.printAllRooms();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}else if (msg[0].equals("RefreshRooms")) {
try {
oos.writeObject("You want list of rooms.");
System.out.println("Print before send.");
rooms.printAllRooms();
oos.writeObject(rooms);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
///EDIT:
So I removed PrintWriter and BufferedReader objects and now Im using only Object Streams. What doesn't work now is:
I create some rooms one after another and then refresh rooms list on clients app - in that case I get all rooms
But when I create one room refresh then create another and refresh I get only 1 room after 2nd refresh, so basically when I refresh server sends me always the same object from 1st send and I don't know how to change it.
Also Im printing these rooms on server side and always get all rooms so room creation is OK.

You could try to flush the buffered streams:
os.flush()
This will force the stream to actually send the bytes of the serialized object. Without that, the BufferedOutputStream might just wait around and buffer data, as the name says. This is done so that the size of the sent packets does not become too small, which would result in a lot of overhead if you want to send multiple objects.
If you are done, you should close the stream anyway.

Java try-with-recourses stuck

I have a classic server-multi-clients program. Tthe server listens to ServerSocket and for each incoming socket it builds a new Runnable class and executes it in ExecuteService.
In the run method of the Runnable class, I open try-with-resources block and in the try I have a while loop that reads from inputstream and writes to outputstream until it receives FIN command from the clients. Everything works fine and the clients disconnect successfully. The run reaches the finally block and prints some stuff for testing, but it doesn't exit the try block so it does not exit the run method and I am stuck in the run somewhere, maybe the read method of the inputstream.
I can post the code if anyone interested.
How can I force close everything in the finally and exit the run method?
The code:
Server.java:
public static void main(String[] args) {
playersReady = new ArrayList<Integer>();
ServerSocket server = null;
try {
server = new ServerSocket(Consts.PORT);
ExecutorService service = Executors.newFixedThreadPool(characters.size());
while(playersReady.size()<characters.size()){
RequestHandler handler = new RequestHandler(server.accept());
service.execute(handler);
}
service.shutdownNow();
service.shutdown();
while(!service.isTerminated()){}
System.out.println("finished");
RequestHandler.java
public final class RequestHandler implements Runnable {
.....
public void run() {
//DataOutputStream output = null;
//DataInputStream input = null;
try (DataOutputStream output = new DataOutputStream(socket.getOutputStream());
DataInputStream input = new DataInputStream(socket.getInputStream())){
// socket.setSoTimeout(500);
handleReady(input.readUTF().split(" "), output);
while (/*!shutdown && !socket.isClosed() && */socket.isConnected()) {
System.out.println("check before read " + character.getId());
String request = input.readUTF();
System.out.println("check after read " + character.getId());
System.out.println("-----------------------------------" + request);
if (shutdown) {
socket.shutdownInput();
socket.getOutputStream().flush();
socket.shutdownOutput();
break;
}
String[] requestParser = request.split(" ");
if (requestParser[1].equals("DMG")) {
// handle damage request
handleDamage(requestParser, output);
} else if (requestParser[1].equals("BND")) {
// handle bandage request
handleBandage(requestParser, output);
} else if (requestParser[1].equals("FIN")) {
// handle finish request
handleFin();
if (!socket.isClosed())
socket.shutdownInput();
if (!socket.isClosed()) {
socket.getOutputStream().flush();
socket.shutdownOutput();
}
shutdown = true;
break;
} else {
break;
}
}
} catch (SocketTimeoutException e) {
System.out.println(e.getMessage());
} catch (IOException e) {
e.printStackTrace();
shutdown = true;
break;
} catch (Throwable e) {
e.printStackTrace();
} finally {
try {
System.out.println("finished");
if (!socket.isClosed())
socket.shutdownInput();
if (!socket.isClosed()) {
socket.getOutputStream().flush();
socket.shutdownOutput();
socket.close();
}
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
System.out.println("Done run");
}
....
The System.out.println("finished") in the finally is printed,
but the System.out.println("Done run") in the end of the run method does not!!
Why?
It stuck in the run method, I think in the readUTF call, but I closed all the resources!

You return before that line, that's why it is not run. The finally block is run anyway, because it is a finally block. Finally blocks are always run, there is only one exception from this rule: System.exit(), but this is not the case.

Starting Threads without Stopping them in my Server Socket causes disconnections

I have a server coded with Java using Eclipse, I am running Android Apps on this server
my two phones and the server are at the same network .
when I connect from the phones two the server I can see the clients connect to the server
and when a client is disconnected I can see that too.
when I connect from the first client then I make a connection from the second client then the first client automatically disconnect for no reason.
which means I can not make two moves on the server without one of the client disconnect.
maybe the thing is that when a client connect to the server a thread is created (myThread) but when the client is disconnected I think the thread (MyThread) is never stopped.
I can see that I get to 30 Thread names.
my question is , if the many threads cause the disconnection, how to stop every thread after the client is diconnected?
public Server() {
// ServerSocket is only opened once !!!
try {
serverSocket = new ServerSocket(6000);
System.out.println("Waiting on port 6000...");
boolean connected = true;
// this method will block until a client will call me
while (connected) {
Socket singleClient = serverSocket.accept();
// add to the list
ServerThread myThread = new ServerThread(singleClient);
allClients.add(myThread);
myThread.start();
}
// here we also close the main server socket
serverSocket.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
class ServerThread extends Thread {
Socket threadSocket;
String userName;
boolean isClientConnected;
InputStream input;
ObjectInputStream ois;
OutputStream output;
ObjectOutputStream oos;
public ServerThread(Socket s) {
threadSocket = s;
}
public void sendText(String text) {
try {
oos.writeObject(text);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void run() {
try {
counter++;
input = threadSocket.getInputStream();
ois = new ObjectInputStream(input);
output = threadSocket.getOutputStream();
oos = new ObjectOutputStream(output);
userName = (String) ois.readObject();
isClientConnected = true;
while (isClientConnected) {
String singleText;
singleText = (String) ois.readObject();
oos.flush();
for (ServerThread t : allClients)
if (t.isAlive())
t.sendText(singleText);
}
// close all resources (streams and sockets)
ois.close();
oos.close();
threadSocket.close();
counter--;
System.out
.println("disconnected : lost connection - connections: "
+ counter);
} catch (Exception e) {
// TODO Auto-generated catch block
counter--;
isClientConnected = false;
System.out.println("Quit App : lost connection - connections: "
+ counter);
}
}
}

i figured it out before, i just removed the userName = (String) ois.readObject(); before the loop and it worked fine .. tHANK YOU ALL
– amjad

Java chatprogram, infinit loop stops

I have to build a chat program.
There is the server class, the client class and two threads to write and receive messages.
the two threads should run in an infinite loop and check all the time if there is an input and print that input afterwards.
But my program works for just one round. So the server and the client can write one single message, afterwards it stops and does not check for another message. Why does the thread not start again from the begin when it's never interrupted? --> see the code beneath
I hope you know what my problem is, it's quite hard for me to describe.
Thread to read a new Message
public class MsgWriter extends Thread {
private Socket s;
public MsgWriter(Socket s){
this.s = s;
}
public void run(){
int i = 0;
OutputStream out = null;
PrintWriter writer;
Scanner input;
while(!interrupted()){
try{
synchronized(s){
input = new Scanner (System.in);
out = s.getOutputStream();
writer = new PrintWriter(out);
String toserver = input.nextLine();
writer.write(toserver);
writer.flush();
System.out.println("me: " + toserver);
}
try {
Thread.sleep((int) (100 * Math.random()));
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}catch(Exception e) {
}
}
}
}
Thread to check if there is a new message and prints it.
public class MsgReader extends Thread {
Socket s;
public MsgReader(Socket s){
this.s = s;
}
public void run() {
int i = 0;
while (!interrupted()) {
try{
synchronized(s){
InputStream in = s.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String s = null;
while((s=reader.readLine()) != null){
System.out.println("d");
}
}
try {
Thread.sleep((int) (100 * 1));
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}catch (Exception e){
}
}
}
}
The Server class starts a new server and waits for a client, afterwards it starts the two threads. The same with the client class, it connects to the server and starts the threads.

You're probably thowing an exception somewhere. In your catch blocks, print the error.
try {
} catch (Exception e) {
System.out.println("Error: " + e);
}

Making a small program part as a bigger one in java. Multithreading?. Noobs

I am working on a small project where I have to communicate to an Android app on my phone and with Arduino.
Now, I have the connection between Android and laptop (used as server, I have a small amount of data stored here), and I can change the contents of text files when I send certain instructions from Android app.
This is how I do it:
I have a ServerSide class that listens on port 3000 and I read the text I stream from phone, then I make certain changes in text files for different messages.
The code:
public class ServerSide {
public static void main(String[] args) throws IOException {
while (true) {
ServerSocket serverSocket = null;
// check if client is trying to connect
try {
serverSocket = new ServerSocket(3000);
} catch (IOException e) {
System.err.println("Cannot communicate on this port");
System.exit(1);
}
Socket clientSocket = null;
// move to another socket
try {
clientSocket = serverSocket.accept();
} catch (IOException e) {
System.err.println("Accept failed");
System.exit(1);
}
// stream that will be sent to client. "true" is for creating from
// existing
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(),
true);
// stream that comes from the client
BufferedReader in = new BufferedReader(new InputStreamReader(
clientSocket.getInputStream()));
String recivedData, sendData;
ServerProtocol communicationProtocol = new ServerProtocol();
while ((recivedData = in.readLine()) != null) {
sendData = communicationProtocol.process(recivedData);
out.println(sendData);
System.out.println("The text should now be written in file");
System.out.println(sendData);
}
in.close();
out.close();
clientSocket.close();
serverSocket.close();
}
}
}
ServerProtocol.process() is the method that updates the files
By the way, this is a good version of a program that implies connection via sockets (if anyone should need information about this, at a future time).
Everything works great, I can see my updates immediatly after I send them, the server is up and running, waiting for messages.
I forgot to mention, I am new to java and a novice in programming, in general.
Now, I want this code I managed to write to be part of a bigger "server". By "server", I understand a program that "serves", performs a service. When it runs on my laptop, it takes information that comes from the Internet on the port I specify, change things in files according to my messages, keeps theese files updated and in the same time it uses theese files to "interpert" data I send from phone, and then sends according messages to Arduino Shield. (THIS IS WHAT I WANT TO ACHIVE)
I guess that what I miss, is the following:
How do i make this code I have written untill now, part of a bigger project, that does all that?
I managed to split the project in 3 parts:
Communication laptop - Android
Constant data updates
Communication laptop - Arduino
I've done some research, and I came across threads. So I thought about having the communication with Android on a separate thread of a MainServer. I clearly got it wrong, because it doesn't do what I expect it to do, so here is the code:
I create the ServerSide class that extends Thread, and has a run() method that should be called when I start the thread. It behaves just like the one above, but the executing code lays inside a run() method:
public class ServerSide extends Thread {
#Override
public void run() {
while (true) {
ServerSocket serverSocket = null;
// check if client is trying to connect
try {
serverSocket = new ServerSocket(3000);
} catch (IOException e) {
System.err.println("Cannot communicate on this port");
System.exit(1);
}
Socket clientSocket = null;
// move to another socket
try {
clientSocket = serverSocket.accept();
} catch (IOException e) {
System.err.println("Accept failed");
System.exit(1);
}
// stream that will be sent to client. "true" is for creating from
// existing
PrintWriter out = null;
try {
out = new PrintWriter(clientSocket.getOutputStream(), true);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// stream that comes from the client
BufferedReader in = null;
try {
in = new BufferedReader(new InputStreamReader(
clientSocket.getInputStream()));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
String recivedData, sendData;
recivedData = null;
sendData = null;
ServerProtocol communicationProtocol = new ServerProtocol();
try {
while ((recivedData = in.readLine()) != null) {
try {
sendData = communicationProtocol.process(recivedData);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
out.println(sendData);
System.out
.println("The text should now be written in file");
System.out.println(sendData);
}
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
in.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
out.close();
try {
clientSocket.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
serverSocket.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
Then, I have the MainServer:
public class MainServer {
public static void main(String[] args) throws IOException {
System.out.println("Started");
Thread myThread = new Thread(new ServerSide());
myThread.start();
System.out.println("Started2");
while (true);
}
}
It should do nothing, just start the new thread. I expect this new thread do act just like the old ServerSide above (the one with main() method).
Someone, please tell me where I got it wrong !?!

Well, two things seem a little unusual about the MainServer class. First, creating a thread with new Thread(new ServerSide()) will cause a compilation error. There are two ways to fix this: either you make ServerSide implement the Runnable interface instead of extending Thread, or you create the thread with new ServerSide(). Second, the infinite loop at the end of main is useless and can be removed. The main method runs in its own thread, and if it finishes, all other threads keep running, and there is no need to keep main alive. The program will indeed keep running when main finishes, which may seem strange, but that's what will happen.

Everything was OK here, my problem was actually my phone connection to wi-fi, I was a bit too far in the back yard :)