I'm trying to create a program for a distributed system. At the moment I have a thread for listening to connections, and a thread for sending, and a thread for receiving.
I've reached a problem where the client will connect but only when using breakpoints. I can't figure out the problem at all!. I've tried to implement things to slow the program down however nothing is working.
If you guys could take a look i'd be greatly appreciative.
public static void main(String[] args)
{
System.out.println("Server starting on port 5000");
RecievingConnection reciever = new RecievingConnection(5000,0); //Recieving Connection
reciever.start();
SendingConnection sender = new SendingConnection(5001,1); //Sending Connection
sender.start();
while(true){
while(reciever.ready==true){
System.out.println("In");
nodes first = new nodes(reciever.socket,0);
System.out.println("Node created");
first.start();
System.out.println("Client connected on port: " + reciever.socket.getLocalAddress());
nodes second = new nodes(sender.socket,1);
second.start();
reciever.ready=false;
sender.ready=false;
reciever.connectionComplete=true;
sender.connectionComplete=true;
}
}
}
public RecievingConnection(int port, int mode)
{
Serverport = port;
connectionMode = mode;
try{
server = new ServerSocket(port);
server.setSoTimeout(100000);
}
catch(IOException ex)
{
System.out.println(ex);
}
}
public void run(){
while(true){
if(ready == false){
try {
socket = server.accept();
ready = true;
System.out.println("Attempting to connect using port: " + Serverport);
while(connectionComplete == false){
//wait
}
} catch (IOException ex) {
System.out.println(ex);
}
}
}
}
The sending thread is basically the same code. Any idea what the problem is? "Nodes" is the thread for each node.
I solved it by adding a sleep in the main thread. I presume this is because the main thread takes priority over child threads?
Your problem is almost certainly at:
while (connectionComplete == false) {
//wait
}
This will loop forever, the other thtreads will not get any cpu time at all. It also explains why it works in debug - it's because in debug if you stop at a breakpoint, any other threads will get time.
You should at least do:
while (connectionComplete == false) {
//wait
Thread.sleep(0);
}
and maybe use a number much greater than 0. This will allow other thtreads a chance to run.
I am not suggesting that this will make your code work correctly but it should remove the current problem.
After that there's another tight loop that won't let any other thread time.
while (true) {
if (ready == false) {
Change that to:
while (true) {
if (ready == false) {
// ...
} else {
// Here too.
Thread.sleep(0);
}
}
You can't just share variables between threads. Make them volatile, synchronize or use CAS types like AtomicBoolean.
Read about it.
https://docs.oracle.com/javase/tutorial/essential/concurrency/interfere.html
http://www.journaldev.com/1061/java-synchronization-and-thread-safety-tutorial-with-examples
https://docs.oracle.com/javase/tutorial/essential/concurrency/atomicvars.html
Besides class "nodes" is not described here and classes are expected to start with an upper case letter.
Related
So what I'm trying to do is have a socket that receives input from the client, put the client into the queue and then return a message to each client in the queue when my algorithm returns true.
This queue should support a few hundred clients at once but at the same time not bottle neck the server so it can actually do what its supposed to do.
This is what i have so far:
private static final int PORT = 25566;
private static final int THREADS = 4;
private ExecutorService service;
public void init() throws IOException, IllegalStateException {
ServerSocket serverSocket;
serverSocket = new ServerSocket(PORT);
service = Executors.newCachedThreadPool();
Socket socket;
while(true) {
socket = serverSocket.accept();
System.out.println
("Connection established with " + socket.getInetAddress().toString());
service.execute(() -> {
Scanner scanner = null;
PrintWriter output = null;
String line = null;
try {
scanner = new Scanner(new InputStreamReader(socket.getInputStream()));
output = new PrintWriter(socket.getOutputStream());
} catch(IOException e) {
e.printStackTrace();
}
try {
if (scanner == null || output == null)
throw new IllegalStateException("Scanner/PrintWriter is " + "null!");
line = scanner.nextLine();
while (line.compareTo("QUIT") != 0) {
/* This is where input comes in, queue for the algorithm,
algorithm happens then returns appropriate values */
output.flush();
line = scanner.nextLine();
}
} finally {
try {
System.out.println
("Closing connection with " + socket.getInetAddress().toString());
if(scanner != null) {
scanner.close();
}
if(output != null) {
output.close();
}
socket.close();
} catch(IOException e) {
e.printStackTrace();
}
}
});
}
}
Now what I think will happen with this, is if the queues do reach high enough levels, my thread pool will completely bottleneck the server as all of the threads are being put to use on handling the clients in the queue and there won't be enough processing for the algorithm.
EDIT: After a bunch of testing, I think it will work out if in the algorithm it returns the value then disconnects, not waiting for user response but having the users client reconnect after certain conditions are met.
Your bottleneck is unlikely to be processing power unless you are machine limited. What's more likely to happen is that all the threads in your thread pool are consumed and end up waiting on input from the clients. Your design can only handle as many clients at once as there are threads in the pool.
For a few hundred clients, you could consider simply creating a thread for each client. The limiting resource for the number of threads that can be supported is typically memory for the stack that each thread requires, not processing power; for a modern machine with ample memory, a thousand threads is not a problem, based on personal experience. There may be an operating system parameter limiting the number of threads which you may have to adjust.
If you need to handle a very large number of clients, you can set up your code to poll sockets for available input and do the processing only for those sockets that have input to be processed.
I have a thread handling a socket connection:
BufferedReader socketInput = new BufferedReader(new InputStreamReader(mySocket.getInputStream()));
while (true)
{
String line = socketInput.readLine();
// do stuff
}
As I've read in a few answers on this site, the recommended solution is to use a flag which one thread sets and my (socket handling) thread checks and terminates itself when that flag changes state. Something like:
while (!done)
{
String line = socketInput.readLine();
// do stuff
}
But this can get stuck when readLine() is still waiting for input. I guess I could set a timeout:
mySocket.setSoTimeout(100);
while (!done)
{
String line = socketInput.readLine();
// do stuff
}
Which would probably work but I would still get a 100 ms delay before my thread "realizes" the flag's state changed.
Is there a way for the thread to "realize" right away that it should end? If not, is my solution (with timeout and flag done) correct?
Edit: I've clarified that the socketInput is of type BufferedReader (alternatively I'm considering Scanner).
The most common way to handle this is to close the socket from the other Thread. This will lead the reading side to unblock and exit with the (expected) error that the socket was closed. Depending on the socket API that you have available it might also be possible to shutdown only the reading side. From a short look at the JDK shutdownInput() might work.
If you however want to continue to read from the socket later on these obvisouly won't work. Your solution should work there, but is obvisouly worse for performance and reactivity since you basically poll the socket all 100ms.
Create a Selector
Configure your socket.getChannel() to non-blocking and register it to the Selector with SelectionKey.OP_READ
Call your Selector select() method that will return when there are some data to read so you can call readLine() (i.e. select() returns > 0)
Whenever you want to end your socket processing, set your done flag and call your Selector wakeup() method. That will make the select() return immediately (potentially 0, or 1 if there was activity). You can then check your done flag and end your thread gracefully.
Here is a quick implementation. Notice I pass the BufferedReader as an argument as if you're opening it in the thread you should also close it there, which would close the socket too, so it has to be done outside. There are two methods to signal the thread to gracefully stop processing input and one to send data:
public class SocketHandler extends Thread {
private Socket sok;
private BufferedReader socketInput;
private Selector sel;
private SocketChannel chan;
private boolean done;
public SocketHandler(Socket sok, BufferedReader socketInput) throws IOException {
this.sok = sok;
chan = sok.getChannel();
chan.configureBlocking(false);
sel = Selector.open();
chan.register(sel, SelectionKey.OP_READ);
this.socketInput = socketInput;
done = false;
}
#Override
public void run() {
while (!done) {
try {
if (sel.select() == 0)
continue;
} catch (IOException e) {
e.printStackTrace();
}
// Only one channel is registered on only one operation so we know exactly what happened.
sel.selectedKeys().clear();
doRead();
// Otherwise: loop through sel.selectedKeys(), check for readability and clear the set
}
try {
sel.close();
} catch (IOException e) {
e.printStackTrace();
}
}
private void doRead() {
try {
String line = socketInput.readLine();
// TODO: process 'line'
} catch (IOException e) {
e.printStackTrace();
}
}
public void signalStop() {
done = true;
if (sel != null)
sel.wakeup(); // Get out of sel.select()
}
public void doWrite(byte[] buffer) throws IOException { // Or "String message"
sok.getOutputStream().write(buffer); // Or anything else
}
}
The solution is correct, it will exit when done is set to true.
And yes, the readLine will always wait for 100ms, if you don't want to wait you may interrupt the thread by calling thread.interrupt() it but it's not very clean way.
The best way to know when finish a socket connection is to try to read something. If read method return -1 you can end threadling socket connection
byte[] data = new byte[2048];
while (!done) {
int count = input.read(data);
if (count <= 0) {
if (count < 0)
done = true;
continue;
}
String request = new String(data, 0, count);
//do stuff
}
We try to read something in input if count == -1, the socket client is disconnected now we can end the loop, by changing the value of done.
I am implementing multiplayer game with server socket mechanism.
Game is running in one loop mechanism.
Server only broadcast any message to every player connected.
Server creates thread for every connected player
Messages are JSONs and they are being sent every 100ms from client side.
Messages are being broadcasted by server and read by client without any interval.
This is server loop:
while (true) {
try {
System.out.println("LISTENING...");
Socket clientSocket = serverSocket.accept();
System.out.println("GOT CONNECTION");
PlayerThread playerThread = new PlayerThread(clientSocket);
playerThread.start();
} catch (IOException e) {
LOGGER.log(Level.SEVERE, "Exception occured on server");
break;
}
}
This is PlayerThread loop:
while (true) {
try {
String inputMessage = in.readUTF();
System.out.println("GOT: " + inputMessage);
JsonNode jsonNode = objectMapper.readTree(inputMessage);
String senderName = jsonNode.get("senderName").asText();
if (!players.contains(this)) {
playerName = senderName;
players.add(this);
}
for (PlayerThread p : players) {
p.getOut().writeUTF(inputMessage);
}
And finally listening to messages:
public void listen() {
if (connected) {
try {
if (in.available() > 0) {
String inputMessage = in.readUTF();
System.out.println("GOT MESSAGE: " + inputMessage);
handleMessages(inputMessage);
}
} catch (IOException e) {
LOGGER.log(Level.INFO, "Connection lost");
connected = false;
}
} else
LOGGER.log(Level.INFO, "Player is not connected");
}
Method above is run in main game loop. It checks if there's something in inputStream and then reads it.
This is how correct message looks like:
GOT MESSAGE: {"type":"UPDATE_STATE","content":null,"senderName":"GRACZ 52","posX":10.0,"posY":5.0}
It works ok when there are 2 players, but the more players connect the more probably is to get message like this (or similiar broken messages):
GOT MESSAGE: 0} U{"type":"UPDATE_STATE","content":null,"senderName":"GRACZ 65","posX":10.0,"posY":5.0}
or
GOT MESSAGE: {"type":"UPDATE_STATE","content":null,"senderName":"GRACZ 24","pos
There different errors in message like Y letter, half-message or multiple messages in one row. Why such thing happen? It looks like when there are more players and they write into output stream in server side, this stream is not read yet so they are appending and appending. But it doesn't explain why there are broken and most imporant, how to resolve it?
I can move reading stream to another thread because in.readUTF() locks process but I wanted to keep it synchronized in main game loop and I don't think this will help (am I wrong?)
You need to synchronize your write loop on an object that's common between all PlayerThreads so that messages don't interleave.
synchronized(/*Should be a "global" server object*/) {
for (PlayerThread p : players) {
p.getOut().writeUTF(inputMessage);
}
}
I have a network client which tries 3 times in a loop to connect to server. During this time I use sleep thread. Is there any way to replace Thread.sleep(700); with some code which skip the waiting period right after the client is connected.
NClient pc;
if (pc == null)
{
try
{
Thread.sleep(700);
}
catch (InterruptedException x)
{
//TODO
}
if (pc != null)
{
outPrint.println("Connected");
break;
}
}
I would like to improve the user experience by reducing the waiting period in which the connection negotiation is in progress. What are the options in Java to do this?
The answer to this question depends on the implementation of NClient. Typically, I'd use a connect timeout for this. The example below indicates how to do this with a Socket. I don't know what NClient is, so I can't give you an NClient example unfortunately.
Create a method that attempts to connect - up to 3 times
Socket connectToServer() {
Socket socket = new Socket();
final int connectTimeoutMs = 700;
for (int i=0; i<3; i++) {
try {
// the call to connect blocks the current thread for a maximum of 700ms if it can't connect
socket.connect(new InetSocketAddress("localhost", 8080), connectTimeoutMs);
} catch (IOException e) {
// failed to successfully connect within 700 milliseconds
e.printStackTrace();
}
}
return socket;
}
Use the above as follows
Socket socket = connectToServer();
if (socket.isConnected()) {
// do stuff with the valid socket!
}
In short, use a connect timeout!
I'm studying the following basic Java socket code( source ). It's a Knock-Knock-Joke client/server app.
In the Client, we set up the socket as usual:
try {
kkSocket = new Socket("localhost", 4444);
out = new PrintWriter(kkSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(kkSocket.getInputStream()));
} catch( UnknownHostException uhe ){ /*...more error catching */
And then later, we just read and write to Server:
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
String fromServer;
String fromUser;
while ((fromServer = in.readLine()) != null) {
System.out.println("Server: " + fromServer);
if (fromServer.equals("bye."))
break;
fromUser = stdIn.readLine();
if (fromUser != null){
System.out.println("Client: " + fromUser);
out.println(fromUser);
}
And on the server, we have the corresponding code, to get the joke punch-line.
KnockKnockProtocol kkp = new KnockKnockProtocol();
outputLine = kkp.processInput(null);
out.println(outputLine);
while ((inputLine = in.readLine()) != null) {
outputLine = kkp.processInput(inputLine);
out.println(outputLine);
if (outputLine.equals("Bye."))
break;
I want to attach a heartbeat to the whole thing, which will print out to the console whenever it detects that the other side died. Because what happens now if I kill the other side is an exception - like this one below:
So if I am running both KnockKnockClient and KnockKnockServer, then I shut down KnockKnockServer, what should happen is that on the Client I see this outputted:
>The system has detected that KnockKnockServer was aborted
I'm looking for any tips. So far I've mainly been trying to run a daemon thread that periodially creates new connections to the other side. But I'm confused about what condition to check for(but I think it's just a boolean value?). Is that the right approach? I just found out online there's a library called JGroups for multicast networking - would that be a better way? I'm looking for any tips.
My server-code so far(sorry it's messy)
&
Client-side
thanks
But the exception you are getting is exactly this! It's telling you that the other side just died. Just catch the exception and print to the console, that "The system has detected that KnockKnockServer was aborted".
You are using TCP connection and TCP has built-in heartbeat (keepalive) mechanism that will do this for you. Just set setKeepAlive() on the socket. That being said - It is possible to control keepalive frequency per each connection, but I do not know how to do that in java.
http://tldp.org/HOWTO/TCP-Keepalive-HOWTO/overview.html
https://stackoverflow.com/a/1480259/706650
you have a Synchronous communication. for having the heartbeat message, use an asynchronous communication. there will be 2 threads. one will read from the socket and another will keep writing to the socket. If you use asynchronous communication, the server will be sending a message every 10 seconds. the client thread will be reading messages from the server and if there is no message, it means the server is down. in your case, the server either sends back the message to client(if client has some message) or send an automatic reply.your server code can be modified like this.
Create a server thread that will keep sending messages to client every 10 seconds.
public class receiver extends Thread{
public static bool hearbeatmessage=true;
Socket clientSocket=new Socket();
PrintWriter out=new PrintWriter();
public receiver(Socket clientsocket){
clientSocket=clientsocket;
out = new PrintWriter(clientSocket.getOutputStream(), true);
}
public void run(){
while(true)
{
if(heartbeatmessage){
thread.sleep(10000);
out.println("heartbeat");
}
}
}
}
In your server code:
KnockKnockProtocol kkp = new KnockKnockProtocol();
outputLine = kkp.processInput(null);
out.println(outputLine);
receiver r=new reciver(clientSocket);
r.run(); /*it will start sending hearbeat messages to clients */
while ((inputLine = in.readLine()) != null) {
outputLine = kkp.processInput(inputLine);
reciver.hearbeatMessage=false; /* since you are going to send a message to client now, sending the heartbeat message is not necessary */
out.println(outputLine);
reciver.hearbeatMessage=true; /*start the loop again*/
if (outputLine.equals("Bye."))
break;
The client code will also be modified, a thread will keep reading messages from the socket and if it has not received message for more than 11 seconds(1 second extra), it will declare the server is not available.
Hope this helps. There might be some flaw in the logic too. Let me know.
The following are best practices which we apply on a daily base when interfacing with hardware (using sockets).
Good practice 1 : SoTimeout
This property enables a read timeout. The goal of this is to avoid the issue that Tom had. He wrote something in the line of : "you will need to wait till the next client message arrives". Well, this offers a solution to that problem. And it's also the key to implementing a heartbeat and many other checks.
By default, the InputStream#read() method will wait forever, until a message arrives. The setSoTimeout(int timeout) changes this behaviour. It will apply a timeout now. When it timeouts it will throw the SocketTimeoutException. Just catch the exception, check a couple of things and continue reading (repeat). So basically, you put your reading method in a loop (and probably even in a dedicated thread).
// example: wait for 200 ms
connection.setSoTimeout(200);
You can use these interruptions (caused by the timeout) to validate the status: E.g. how long has it been since I received my last message.
Here is an example to implement the loop:
while (active)
{
try
{
// some function that parses the message
// this method uses the InputStream#read() method internally.
code = readData();
if (code == null) continue;
lastRead = System.currentTimeMillis();
// the heartbeat message itself should be ignored, has no functional meaning.
if (MSG_HEARTBEAT.equals(code)) continue;
//TODO FORWARD MESSAGE TO ACTION LISTENERS
}
catch (SocketTimeoutException ste)
{
// in a typical situation the soTimeout should be about 200ms
// the heartbeat interval is usually a couple of seconds.
// and the heartbeat timeout interval a couple of seconds more.
if ((heartbeatTimeoutInterval > 0) &&
((System.currentTimeMillis() - lastRead) > heartbeatTimeoutInterval))
{
// no reply to heartbeat received.
// end the loop and perform a reconnect.
break;
}
// simple read timeout
}
}
Another use of this timeout: It can be used to cleanly stop your session by setting active = false. Use the timeout to check if this field is true. If that's the case, then break the loop. Without the SoTimeout logic this would not be possible. You would either be forced to do a socket.close() or to wait for the next client message (which clearly makes no sense).
Good practice 2 : Built-in Keep-Alive
connection.setKeepAlive(true);
Well basically this is pretty much what your heart-beat logic does. It automatically sends a signal after a period of inactivity and checks for a reply. The keep-alive interval is operating system dependent though, and has some shortcomings.
Good practice 3 : Tcp No-Delay
Use the following setting when you are often interfacing small commands that need to be handled quickly.
try
{
connection.setTcpNoDelay(true);
}
catch (SocketException e)
{
}
I think you are over complicating things.
From the client side:
If the client gets an IOException for the connection reset, then this means the server is dead. Instead of printing the stack trace just do what ever you need to do once you know that the server is down. You already know the server is down due to the exception.
From the server side:
Either start a timer and if you don't get a request for a time more than the interval assume that the client is down.
OR start a background server thread at the client (making the client and server peers) and have the server send a "dummy" hearbeat request (server now acts as a client). If you get exception the client is down.
Figured I'd take a crack at this... I started with the KnockKnockServer and KnockKnockClient that are on the Java site (in your original question).
I didn't add any threading, or heartbeats; I simply changed the KnockKnockClient to the following:
try { // added try-catch-finally block
while ((fromServer = in.readLine()) != null) {
System.out.println("Server: " + fromServer);
if (fromServer.equals("Bye."))
break;
fromUser = stdIn.readLine();
if (fromUser != null) {
System.out.println("Client: " + fromUser);
out.println(fromUser);
}
}
} catch (java.net.SocketException e) { // catch java.net.SocketException
// print the message you were looking for
System.out.println("The system has detected that KnockKnockServer was aborted");
} finally {
// this code will be executed if a different exception is thrown,
// or if everything goes as planned (ensure no resource leaks)
out.close();
in.close();
stdIn.close();
kkSocket.close();
}
This seems to do what you want (even though I modified the original Java website example, rather than your code - hopefully you'll be able to see where it plugs in). I tested it with the case you described (shut down the server while the client is connected).
The downside to this is that, while the client is waiting for user input, you don't see that the server has died; you have to enter client input, and then you'll see that the server has died. If this is not the behavior you want, please post a comment (perhaps that was the whole point of the question - it just seemed like you might have been going down a longer road than you needed in order to get to where you wanted to be).
Here's a slight modification to the client. It doesn't use an explicit heartbeat, but as long as you keep reading from the server, you'll immediately detect the disconnect anyway.
This is because readLine will immediately detect any read errors.
// I'm using an anonymous class here, so we need
// to have the reader final.
final BufferedReader reader = in;
// Decouple reads from user input using a separate thread:
new Thread()
{
public void run()
{
try
{
String fromServer;
while ((fromServer = reader.readLine()) != null)
{
System.out.println("Server: " + fromServer);
if (fromServer.equals("Bye."))
{
System.exit(0);
}
}
}
catch (IOException e) {}
// When we get an exception or readLine returns null,
// that will be because the server disconnected or
// because we did. The line-break makes output look better if we
// were in the middle of writing something.
System.out.println("\nServer disconnected.");
System.exit(0);
}
}.start();
// Now we can just read from user input and send to server independently:
while (true)
{
String fromUser = stdIn.readLine();
if (fromUser != null)
{
System.out.println("Client: " + fromUser);
out.println(fromUser);
}
}
In this case, we allow client writes even when we're waiting for reply from the server. For a more stable application, we'd want to lock the input while we're waiting for a reply by adding a semaphore controlling when we start reading.
These are the modifications we would make to control the input:
final BufferedReader reader = in;
// Set up a shared semaphore to control client input.
final Semaphore semaphore = new Semaphore(1);
// Remove the first permit.
semaphore.acquireUninterruptibly();
new Thread()
... code omitted ...
System.out.println("Server: " + fromServer);
// Release the current permit.
semaphore.release();
if (fromServer.equals("Bye."))
... code omitted ...
while (true)
{
semaphore.acquireUninterruptibly();
String fromUser = stdIn.readLine();
... rest of the code as in the original ...
I think #Bala's answer is correct on server side. I'd like to give a supplementary on client side.
On client side, you should:
use an variable to keep the timestamp of the last message from server;
start a thread which runs periodically(every 1 second, e.g.) to compare current timestamp and the last message timestamp, if it is longer than desired timeout(10 seconds, e.g.), a disconnection should be reported.
Following are some code snippet:
The TimeoutChecker class(thread):
static class TimeoutChecker implements Runnable {
// timeout is set to 10 seconds
final long timeout = TimeUnit.SECONDS.toMillis(10);
// note the use of volatile to make sure the update to this variable thread-safe
volatile long lastMessageTimestamp;
public TimeoutChecker(long ts) {
this.lastMessageTimestamp = ts;
}
#Override
public void run() {
if ((System.currentTimeMillis() - lastMessageTimestamp) > timeout) {
System.out.println("timeout!");
}
}
}
Start the TimeoutChecker after connection is established:
try {
kkSocket = new Socket("localhost", 4444);
// create TimeoutChecker with current timestamp.
TimeoutChecker checker = new TimeoutChecker(System.currentTimeMillis());
// schedule the task to run on every 1 second.
ses.scheduleAtFixedRate(, 1, 1,
TimeUnit.SECONDS);
out = new PrintWriter(kkSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(kkSocket.getInputStream()));
} catch( UnknownHostException uhe ){ /*...more error catching */
The ses is a ScheduledExecutorService:
ScheduledExecutorService ses = Executors.newScheduledThreadPool(1);
And remember to update the timestamp when receiving messages from server:
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
String fromServer;
String fromUser;
while ((fromServer = in.readLine()) != null) {
// update the message timestamp
checker.lastMessageTimestamp = System.currentTimeMillis();
System.out.println("Server: " + fromServer);
if (fromServer.equals("bye."))
break;
Adel,was looking at your code http://pastebin.com/53vYaECK
Can you try the following solution. not sure whether it will work.
instead of creating a bufferedreader with the inputstream once,
we can create an instance of BufferedReader eachtime.
when the kkSocket.getInputStream is null, it comes out of the while loop and set completeLoop to false, so that we exit the while loop.
it has 2 while loops and the objects are created each time.
if the connection is open but does not have data in it inputstream will not be null,
BufferedReader.readLine would be null.
bool completeLoop=true;
while(completeLoop) {
while((inputstream is=kkSocket.getInputStream())!=null) /*if this is null it means the socket is closed*/
{
BufferedReader in = new BufferedReader( new InputStreamReader(is));
while ((fromServer = in.readLine()) != null) {
System.out.println("Server: " + fromServer);
if (fromServer.equals("Bye."))
break;
fromUser = stdIn.readLine();
if (fromUser != null) {
System.out.println("Client: " + fromUser);
out.println(fromUser);
}
}
}
completeLoop=false;
System.out.println('The connection is closed');
}