Develop Reference

Multiplayer Java game - program freeze when starting Server via GUI

I'm writing a Java GUI multiplayer game.
I have a GUI where user can enter port number and click on "start server" which will initiate game server and bring up another GUI frame. But my program freezes when the button is clicked.
Is it okay to start server using this way or how can I code so that server will be started and waiting for players to be connected and at the same time display another GUI frame (written in a separate class)? Thanks in advance.
// part of GUI code
start = new JButton ("Start Game Server");
start.addActionListener (new ActionListener() {
public void actionPerformed (ActionEvent event) {
DEFAULT_PORT = Integer.parseInt(port.getText());
fgServer.run();
fgServerFrame = new FishingGameServerFrame();
//frame.dispose();
}
});
--
// server code
public class FishingGameServer {
private static int DEFAULT_PORT = 0;
public void run()
{
int port = DEFAULT_PORT;
port = Integer.parseInt(FishingGameConnectServerFrame.portNumber());
System.out.println("port #: " + port);
//setup server socket
ServerSocket reception_socket = null;
try {
reception_socket = new ServerSocket (port);
System.out.println("Started server on port " + port);
}
catch (IOException e) {
//to get text in GUI frame
System.out.println("Cannot create server");
System.exit(0);
}
for (;;) {
Socket client_socket = null;
try {
client_socket = reception_socket.accept();
System.out.println("Accepting requests from:" + client_socket.getInetAddress());
}
catch (IOException i) {
System.out.println ("Problem accepting client socket");
}
new FishingGameThreadedServer(client_socket);
}
}
public static void main (String[] args) {
new FishingGameServer().run();
}

You call fgServer.run();, which eventually calls client_socket = reception_socket.accept(); within an infinite loop.
This is preventing the Event Dispatching Thread from been able to run, by blocking (once within the neverending for-loop and once when using accept) it can not process the Event Queue, which is responsible for, amongst other things, processing paint requests.
Swing is a single threaded environment, it is also not thread safe. This means:
You should never perform any long running or blocking operations within the context of the EDT and
All updates and interactions with the UI must be made from within the context of the EDT
Take a look at Concurrency in Swing for more details
You could use a Thread instead or a SwingWorker which provides functionality to more easily publish updates back to the EDT...

My GUI freezes after I recreate a ServerSocket

My Server is build around support to update the listening socket, by doing so I use the following method. my problem occurs after this method is called for the second time, this is first called at start up from the main method then later it is called by clicking a button in a JFrame. what happens is that the JFrame freezes when this method is called via button, as you can see by the code I tried to make this method run a server in a new thread but it hasn't changed my outcome. Does anyone know how to fix this? or at least what is causing it? also any code after the method is called in the main doesn't get execute, so I believe it is a thread problem. (MiniServer extends Thread and is used to handle each connected client individually)
public static void startListening(final int port)
{
listeningThread = new Thread()
{
public void run()
{
try {
serverSocket = new ServerSocket(port);
while(!stop)
{
boolean loop = true;
while (loop)
{
serverSocket.setSoTimeout(1000);
try{
clientSocket = serverSocket.accept();
loop = false;
} catch (SocketTimeoutException e){
}
}
if(!clientSocket.equals(null))
{
MiniServer mini = new MiniServer(clientSocket);
mini.start();
clientSocket = null;
}
}
} catch (IOException e) {
}
}
};
listeningThread.run();
}

You need to be calling listeningThread.start(), which will create a new thread. Right now, you're just calling the thread's run() method on the current thread. The first time you do that it works, since you're on the main thread. The second time, though, you're on the UI thread, reacting to the button press. This causes your UI thread to block.

Components I used to draw a form won't appear after compile

I'm trying to create a chat program in java but I had a problem when I run the server form, that the components I used to draw won't appear.
this is the code I used in the run of the form :
public void run() {
Server s = new Server();
s.setVisible(true);
// Etablir la connexion
try
{
ServerSocket ecoute;
ecoute = new ServerSocket(1111);
Socket service = null;
System.out.println("Serveur en attente d'un client !");
while(true)
{
service = ecoute.accept();
System.out.println("Client connécté !");
DataInputStream is = new DataInputStream(service.getInputStream());
s.jTextArea1.setText("Client dit : " + is.readUTF().toUpperCase());
service.close();
}
}
catch(IOException e)
{
e.printStackTrace();
}
}

You said nothing happens when this code is ran. The presence of a public void run() method tells me that this is a thread, or at least a Runnable.
Because of the while(true), if this thread is not started in the proper manner, it will not run independently; that is it will hold up the entire program.
Instead of calling thread.run();, call thread.start();. This will call the run method for you, after starting a new thread that will run in parallel to the main thread.
If this code is not in a thread, and you just used public void run() by chance, then it will still provide the same problem for you.
For more information, refer to the Documentation on Threads

How to run multiple threads concurrently for Automated Selenium testing?

I have one web application from which I can start respective testing process which is in another Java app. I am using Socket Programming for communication between Web app and Java app.
When I request for specific process from web app then SocketServer from Java app hears request and start one thread for Testing process.
Testing process will initialize FirefoxDriver and start browser and do further test process.
My problem is, when I request for another process with different process name then It again creates second thread and start firefox browser but this time it is not considering my second process, it started to do same process which is first thread have.
I do not understand what to do...For every process I created a new thread but further it will doing same process.
My inputs are correctly received at Java app.
Please help me How can I do the concurrent thread safe processing?
I am using GWT,Java, Seleniun FirefoxDriver.
here is the Server code which is running in background and listen client request:
static final int PORT = 6789;
public static void main(String args[]) {
ServerSocket serverSocket = null;
Socket socket = null;
try {
InitializeApplication application = new InitializeApplication();
application.initialize();
serverSocket = new ServerSocket(PORT);
} catch (Exception e) {
log("Exception in SocketServerExecutor !!!",e);
}
while (true) {
try {
socket = serverSocket.accept();
} catch (Exception e) {
log("Exception in SocketServerExecutor !!!",e);
}
Thread thread = new Thread(new SocketServerThread(socket));
thread.start();
}
}
and this is the Thread which start process:
private Socket client;
public SocketServerThread(Socket serverSocket) {
this.client = serverSocket;
}
/**
* Starts appropriate process depending on process name from input.
* Input string contains:
* process name
*/
public void run() {
DataOutputStream outputStream = null;
String param = null;
try{
log("Just connected to "+ client.getRemoteSocketAddress());
try {
while ((param = in.readUTF()) != null){
log("got parameteres from client (i.e. from web app): "+param);
break;
}
} catch (Exception e) { }
if(param!=null && !param.isEmpty()){
String process = params[0];
ProcessManager manager = new ProcessManager();
if(process.equals("testUser"))
manager.startUserProcess(process);
else if(process.equals("testCustomer"))
manager.startCustomerProcess(process);
}
}catch(Exception exc){
if(exc instanceof SocketTimeoutException)
log("Socket timed out! [SocketServerThread]",exc);
else if(exc instanceof BindException)
log("BindException in SocketServerThread !!!",exc);
log(Level.SEVERE, "Exception in SocketServerThread !!!",exc);
}
}
and this is ProcessManager:
public void starUserProcess(String siteName) {
ExecutorService executerService = null;
try{
Callable<Object> callable = new ProcessThread(siteName);
executerService = Executors.newCachedThreadPool();
Future<Object> future = executerService.submit(callable);
future.get();
log("[ProcessManager] Process completed for "+process);
System.exit(0);
}catch (Exception e) {
log("[ProcessManager]::Exception");
log(ex);
}
}
ProcessThread will initialize all required things and Firefox browser and start process.
Client is new every time which contains input.

One of two things that I can thing of off the top of my head could be happening.
You are passing a paramater into your run() function that links back to the initial thread or...
You are using a shared variable that is accessible to all threads and the variable is either not being updated properly, or not being updated at all.
If you could include an SSCCE, that would help us determine where the problem truly lies.

Got the solution: I created the ExecutorService using newSingleThreadExecutor() instead of newCachedThreadPool() and also setDeamon(True) for every newly created ServerThread.
Here is the Executor documentation

JAVA - Socket.accept() freezes ui

I'm trying to make a multithreaded server/client app with java ! this code is for listen() method in a class of a package that named Bsocket (iserver.core.socket) :
try {
serverSocket = new ServerSocket(port);
}catch(IOException e ){
ui.log(e.toString());//*
}
while (true){
try{
clienSocket = serverSocket.accept();
ui.log("Incomming Connection.");//*
new connectionHandler(clienSocket, ui);
}catch(IOException e ){
ui.log(e.toString());
}
}
ui.log("Incomming Connection."); is a method in below of main class of Bgui (iserver.core.ui).Bgui is a jframe that contain a textarea and something else ! the problem is when the accept methods executed , the ui.log did not works ! whats wrong here ?

You will need to launch your server on a seperate thread since .accept is a blocking call. You might want to do something like so:
(new Runnable() {
#Override
public void run()
{
try {
serverSocket = new ServerSocket(port);
}catch(IOException e ){
ui.log(e.toString());//*
}
while (true){
try{
clienSocket = serverSocket.accept();
ui.log("Incomming Connection.");//*
new connectionHandler(clienSocket, ui);
}catch(IOException e ){
ui.log(e.toString());
}
}
}
}).start();
NOTE: This code is not tested, but it should give you an idea of what you need to do.

Socket.accept() blocks until there's an incoming connection to receive (see the documentation). You shouldn't be making any blocking calls from your UI thread - otherwise it will... you know... block!

You need to separate UI threads from your own network service threads. accept() is blocking (obviously) and it freezes your application until you get a new client, and freezes again waiting for more clients.