Develop Reference

Multithread Server and Client with sockets in Java

I am trying to create for a university project a server / slave / client project.
The server should open 2 ports, one port will be for the connection of the slave and another port for the client.
I have setup 2 threads 1 for the client and another for the slave. The client should sent random numbers to server and server should forward randomly those numbers to slave instances. The slave should check if the current number exist on their list and if it's not available to store it, otherwise they should sent a message to server that the number already exist.
Then I created the client thread which consist of 2 threads, one for sending the numbers to server and another thread to read messages coming from the server.
There is something wrong with the code of the PrintWriter, I cannot make it to send the numbers to server when the code is inside the thread. If I move the code on the main and cancel the thread the messages are being sent without any issue.
What could be the issue for this?
Below is the current code from server (master) and the client.
public class Client {
private static final int NUMBERS = 50;
private static final int AMPLITUDE = 100;
private static int masterPort;
public Client(int port) {
this.masterPort = port;
}
public static void main(String[] args) throws IOException{
String serverHostname = "127.0.0.1";
System.out.println("Αναμονή για σύνδεση στον σέρβερ " + serverHostname + " στην πόρτα 30091.");
Socket echoSocket = null;
BufferedReader in = null;
try {
echoSocket = new Socket(serverHostname, 18889);
in = new BufferedReader(new InputStreamReader(echoSocket.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Δεν μπορεί να πραγματοποιηθεί σύνδεση με τον σέρβερ: " + serverHostname);
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to: " + serverHostname);
System.exit(1);
}
ClientOut clientOut = new ClientOut(echoSocket);
clientOut.start();
ClientIn clientIn = new ClientIn(in);
clientIn.start();
in.close();
echoSocket.close();
}
public static class ClientOut extends Thread {
private PrintWriter out;
public ClientOut(Socket echoSocket) throws IOException {
this.out = new PrintWriter(echoSocket.getOutputStream(), true);
}
#Override
public void run() {
System.out.println("Ο client συνδέθηκε!");
Random rnd = new Random();
try {
for (int i=0; i<NUMBERS; i++) {
int num = rnd.nextInt(AMPLITUDE);
System.out.println(num);
out.println(num);
TimeUnit.SECONDS.sleep(1);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
out.close();
}
}
public static class ClientIn extends Thread {
private BufferedReader in;
public ClientIn(BufferedReader in) {
this.in = in;
}
#Override
public void run() {
}
}
}
public class Master {
private int slavePort;
private int clientPort;
private SlaveThread slaveThread;
private ClientThread clientThread;
private boolean running = false;
public static int slaveConnected; // Slave connection counter
public Master(int slavePort, int clientPort) {
this.slavePort = slavePort;
this.clientPort = clientPort;
this.slaveConnected = 0;
public void startServer() {
try {
this.slaveThread = new SlaveThread(slavePort);
this.clientThread = new ClientThread(clientPort);
System.out.println( "Αναμονή για σύνδεση client / slave" );
slaveThread.start();
clientThread.start();
} catch (IOException e) {
e.printStackTrace();
}
}
public void stopServer() {
running = false;
this.slaveThread.interrupt();
this.clientThread.interrupt();
}
class SlaveThread extends Thread {
private ServerSocket slaveSocket;
SlaveThread(int slavePort) throws IOException {
this.slaveSocket = new ServerSocket(slavePort);
}
#Override
public void run() {
running = true;
while (running) {
try {
// Call accept() to receive the next connection
Socket slSocket = slaveSocket.accept();
System.out.println("Δημιουργήθηκε μια νέα σύνδεση Slave");
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
class ClientThread extends Thread {
private ServerSocket clientSocket;
ClientThread(int clientPort) throws IOException {
this.clientSocket = new ServerSocket(clientPort);
}
#Override
public void run() {
running = true;
while (running) {
try {
Socket clSocket = clientSocket.accept();
BufferedReader in = new BufferedReader(new InputStreamReader(clSocket.getInputStream()));
System.out.println("Δημιουργήθηκε μια νέα σύνδεση Client");
String inputLine;
while ((inputLine = in.readLine()) != null) {
System.out.println("Client: " + inputLine);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
public static void main(String[] args) {
Master server = new Master( 30091, 18889);
server.startServer();
// Automatically shutdown in 1 minute
try {
Thread.sleep( 60000 );
} catch(Exception e) {
e.printStackTrace();
}
server.stopServer();
}

I found the solution.
The Socket should be created on the Client Thread constructor and not to be passed as reference.
So the client should be
public class Client {
private static final int NUMBERS = 50;
private static final int AMPLITUDE = 100;
private static int masterPort;
public Client(int port) {
this.masterPort = port;
}
public static void main(String[] args) throws IOException{
String serverHostname = "127.0.0.1"; //Ορίζουμε την διεύθυνση που είναι ο σέρβερ
System.out.println("Αναμονή για σύνδεση στον σέρβερ " + serverHostname + " στην πόρτα 30091.");
ClientOut clientOut = new ClientOut(serverHostname);
clientOut.start();
ClientIn clientIn = new ClientIn(serverHostname);
clientIn.start();
}
public static class ClientOut extends Thread {
private Socket echoSocket;
private PrintWriter writer;
ClientOut(String serverHostname) throws IOException {
this.echoSocket = new Socket(serverHostname, 18889);
this.writer = new PrintWriter(echoSocket.getOutputStream(), true);;
}
#Override
public void run() {
System.out.println("Ο client συνδέθηκε!");
Random rnd = new Random();
try {
for (int i=0; i<NUMBERS; i++) {
int num = rnd.nextInt(AMPLITUDE);
System.out.println(num);
writer.println(num);
TimeUnit.SECONDS.sleep(1);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
writer.close();
}
}

Java Server-Client with Multiple Client

I have been trying to make a multiple client chatting apps for a few days, and I have read the document below, and find some suggestions online, and I come up with the below code.
https://docs.oracle.com/javase/tutorial/networking/sockets/clientServer.html#later
What I am thinking is to make an app and start the Server, and Send the Message by the methods
"startServer();" and
"sendFromServer(Serializable data)";
~~~~~The Problem is I start startServer() method the app turn frozen, so I know I am doing it the wrong way.~~~~~~~~
Can anyone please give me some hint on how to correctly create a multiple client-server app?
public class Server {
private ServerSocket server;
private Socket socket;
private int port;
private Consumer<Serializable> consume;
private ConnectionThread thread;
private List<ConnectionThread> threads =
new ArrayList<ConnectionThread>();
public Server(int port, Consumer<Serializable> consume){
this.port= port;
this.consume = consume;
try {
server = new ServerSocket(port);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void startServer() {
if(server == null) {
System.out.println("no server");
}
while(true) {
try {
socket = server.accept();
} catch (IOException e) {
e.printStackTrace();
}
ConnectionThread thread =new ConnectionThread(socket);
threads.add(thread);
thread.start();
}
}
public void sendFromServer(Serializable data) throws IOException {
thread.out.writeObject(data);
}
private class ConnectionThread extends Thread {
private Socket socket;
private ObjectOutputStream out;
private ConnectionThread(Socket socket){
this.socket = socket;
}
#Override
public void run(){
try {
ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
this.out = out;
while(true){
Serializable data = (Serializable)in.readObject();
consume.accept(data);
}
}catch (IOException e){
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
}
Client Side: (I am trying to make one Pane holding the two chats at the moment, using two buttons to call the"startServer();" and "startClient();" respectively)
public class Client {
private int port;
private String ip;
private Consumer<Serializable> consume;
private ConnectionThread thread = new ConnectionThread();
public Client(int port, String ip, Consumer<Serializable> consume){
this.port = port;
this.ip = ip;
this.consume = consume;
}
public void startClient(){
thread.start();
}
public void sendFromClient(Serializable data) throws IOException{
thread.out.writeObject(data);
}
private class ConnectionThread extends Thread{
private Socket socket;
private ObjectOutputStream out;
#Override
public void run(){
try(
Socket socket = new Socket(ip, port);
ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
) {
this.out = out;
while(true){
Serializable data = (Serializable)in.readObject();
consume.accept(data);
}
} catch (Exception e) {
e.printStackTrace();;
}
}
}
}
the FXML controller class
public class chatController{
#FXML private TextArea SerBoard, CliBoard;
#FXML private TextField SerTxt,CliTxt;
#FXML private Button SerConnect, CliConnect;
private Server server = createSer();
private Client client = createCli();
private int port= 5555;
private String ip = "localhost";
private boolean connected =
(server==null && client==null)? false: true;
#FXML
public void setOnSerConnect(ActionEvent event) {
server.startServer();
}
#FXML
public void setOnCliConnect(ActionEvent event) {
client.startClient();
}
private Client createCli() {
Client client = new Client(port, ip, data->{
Platform.runLater(() -> {
CliBoard.appendText(data.toString());
});
});
System.out.println("Client connect");
return client;
}
private Server createSer() {
Server server = new Server(port, data->{
Platform.runLater(()->{
SerBoard.appendText(data.toString());
});
});
System.out.println("Server connect");
return server;
}
#FXML
public void setOnSerText(ActionEvent event) {
if(connected) {
String input = SerTxt.getText();
String mes = "Server: "+ input + "\n";
SerTxt.clear();
SerBoard.appendText(mes);
try {
server.sendFromServer(mes);
} catch (IOException e) {
e.printStackTrace();
}
}
}
#FXML
public void setOnCliText(ActionEvent event) {
if(connected) {
String input = SerTxt.getText();
String mes = "Client: "+ input + "\n";
SerTxt.clear();
SerBoard.appendText(mes);
try {
client.sendFromClient(mes);
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

Should be rather
public void startServer() {
if(server == null) {
System.out.println("no server");
}
while(true) {
try {
socket = server.accept();
ConnectionThread thread =new ConnectionThread(socket);
threads.add(thread);
thread.start();
} catch (IOException e) {
e.printStackTrace();
}
}
This way u will acceppt all client connections.
Also startServer must be invoked using Platform.runLater as well.

Java socket: Connection reset

I have browsed, searched ... and nothing sparkles to my mind!
I am running a chat type service between a server and an Android app. The client connects, the server registers the socket, and every 10 minutes the server sends to all connected devices a message.
My problem is that randomly I have a connection reset exception. I can not trace back when the problem occurs.
My server side code is:
final public class ChatRoomService {
private final static String AUTHENTICATE = "AUTHENTICATE";
private final static String BROADCAST = "BROADCAST";
private final static String DISCONNECT = "DISCONNECT";
private final static String OK = "OK";
private final static String NOK = "NK";
private final static Logger LOGGER = Logger.getLogger(ChatRoomService.class);
private ServerSocket listener = null;
#Inject
private EntityManager entityManager;
public EntityManager getEntityManager() {
return entityManager;
}
#Inject
private PlayerManager playerManager;
PlayerManager getPlayerManager() {
return playerManager;
}
private static HashSet<ChatRoomConnection> connections = new HashSet<ChatRoomConnection>();
public void addConnection(ChatRoomConnection c) {
synchronized(connections) {
connections.add(c);
}
}
public void removeConnection(ChatRoomConnection c) {
synchronized(connections) {
connections.remove(c);
}
}
public void startListeningToChatRoomConnection() throws IOException {
listener = new ServerSocket(9010);
try {
LOGGER.infof("startListening - Start listening on port %s", 9010);
while (true) {
ChatRoomConnection connection = new ChatRoomConnection(listener.accept(), this);
addConnection(connection);
connection.start();
}
} catch (IOException e) {
if (!listener.isClosed())
LOGGER.errorf("listenToChatRoomConnection - Connection lost during connection: %s", e.getMessage());
} finally {
if (listener != null && !listener.isClosed()) {
LOGGER.infof("listenToChatRoomConnection - Stop listening");
listener.close();
}
}
}
public void stopListeningToChatRoomConnection() throws IOException {
if (!listener.isClosed()) {
LOGGER.infof("stopListeningToChatRoomConnection - Stop listening");
listener.close();
listener = null;
// Closing all sockets
for (ChatRoomConnection connection : connections) {
connection.close();
}
// Clear up the connections list
synchronized (connections) {
connections.clear();
}
}
}
public void broadcastToChatRoomClients(Object message) {
synchronized (connections) {
// Log
LOGGER.debugf("Broadcast ChatRoom: %s - %s",
connections.size(),
message.toString());
for (ChatRoomConnection connection : connections) {
LOGGER.debugf("Broadcast ChatRoom to %s", connection.userName);
connection.publish(message);
}
}
}
private ChatRoomService() {
}
private static class ChatRoomConnection extends Thread {
private Socket socket;
private BufferedReader readerFromClient;
private PrintWriter writerToClient;
public String userName;
private ChatRoomService chatCService;
ChatRoomConnection(Socket socket, ChatRoomService chatRoomService) {
super("ChatRoomConnection");
this.socket = socket;
this.chatRoomService = chatRoomService;
}
public void run() {
try {
readerFromClient = new BufferedReader(new InputStreamReader(socket.getInputStream()));
writerToClient = new PrintWriter(socket.getOutputStream(), true);
// 1- Authenticate the Device/ Player
writerToClient.println(ChatRoomService.AUTHENTICATE);
writerToClient.flush();
Gson gson = new Gson();
Request request = gson.fromJson(readerFromClient.readLine(), Request.class);
if (chatRoomService.getPlayerManager().isPlayerSignedIn(request.getPlayerId(), request.getSignedInOn())) {
Player player = (Player) chatRoomService.getEntityManager().find(Player.class, request.getPlayerId());
userName = player.getUsername();
LOGGER.infof("listenToChatRoomConnection - Connection established with %s", userName);
writerToClient.println(ChatRoomService.OK);
writerToClient.flush();
while (true)
if ((readerFromClient.readLine() == null) ||
(readerFromClient.readLine().startsWith(ChatRoomService.DISCONNECT)))
break;
} else {
writerToClient.println(ChatRoomService.NOK);
writerToClient.flush();
}
} catch (Exception e) {
LOGGER.errorf("listenToChatRoomConnection - Error with %s: %s", userName, e.getMessage());
e.printStackTrace();
} finally {
try {
if (!socket.isClosed()) {
LOGGER.infof("listenToChatRoomConnection - Connection closed by the client for %s", userName);
socket.close();
}
} catch (IOException e) {
LOGGER.errorf("listenToChatRoomConnection - Can not close socket: %s", e.getMessage());
e.printStackTrace();
} finally {
chatRoomService.removeConnection(this);
}
}
}
public void publish(Object message) {
if (!socket.isClosed()) {
writerToClient.println(ChatRoomService.BROADCAST);
Gson gson = new Gson();
writerToClient.println(gson.toJson(message));
}
}
public void close() {
writerToClient.println(ChatRoomService.DISCONNECT);
try {
LOGGER.infof("listenToChatRoomConnection - Connection closed by the server for %s", userName);
socket.close();
} catch (IOException e) {
LOGGER.errorf("Error when trying to close a socket: %s", e.getMessage());
e.printStackTrace();
}
}
};
}
The device code is:
public class ServerBroadcastManager {
private static final String TAG = ServerBroadcastManager.class.getName();
// Type of messages from the server
static public String AUTHENTICATE = "AUTHENTICATE";
static public String DISCONNECT = "DISCONNECT";
static public String BROADCAST = "BROADCAST";
static public String OK = "OK";
static public String NOK = "NK";
private int networkPort;
private ServerBroadcastListener broadcastListener;
private Socket networkSocket;
BufferedReader in;
PrintWriter out;
public ServerBroadcastManager(Context context, ServerBroadcastListener listener, int port) {
this.networkPort = port;
this.broadcastListener = listener;
}
public void startListening(final Context context) {
Runnable run = new Runnable() {
#Override
public void run() {
// Make connection and initialize streams
try {
networkSocket = new Socket();
networkSocket.connect(new InetSocketAddress(mydomain, networkPort), 30*1000);
in = new BufferedReader(new InputStreamReader(
networkSocket.getInputStream()));
out = new PrintWriter(networkSocket.getOutputStream(), true);
// Process all messages from server, according to the protocol.
while (true) {
String line = in.readLine();
if (line.startsWith(ServerBroadcastManager.AUTHENTICATE)) {
Request request = formatAuthenticateRequest(context);
Gson requestGson = new Gson();
out.println(requestGson.toJson(request));
out.flush();
// Waiting for confirmation back
line = in.readLine();
if (line.startsWith(ServerBroadcastManager.OK)) {
} else if (line.startsWith(ServerBroadcastManager.NOK)) {
}
} else if (line.startsWith(ServerBroadcastManager.BROADCAST)) {
Gson gson = new Gson();
#SuppressWarnings("unchecked")
LinkedHashMap<String,String> broadcast = gson.fromJson(in.readLine(), LinkedHashMap.class);
broadcastListener.processBroadcast(broadcast);
} else if (line.startsWith(ServerBroadcastManager.DISCONNECT)) {
break;
}
}
} catch (UnknownHostException e) {
Log.i(TAG, "Can not resolve hostname");
} catch (SocketTimeoutException e) {
Log.i(TAG, "Connection Timed-out");
broadcastListener.connectionFailed();
} catch (IOException e) {
Log.i(TAG, "Connection raised on exception: " + e.getMessage());
if (!networkSocket.isClosed()) {
broadcastListener.connectionLost();
}
}
}
};
Thread thread = new Thread(run);
thread.start();
}
public void stopListening() {
try {
if (networkSocket != null)
networkSocket.close();
} catch (IOException e) {
Log.i(TAG, "Exception in stopListening: " + e.getMessage());
}
}
private Request formatAuthenticateRequest(Context context) {
Request request = new Request();
SharedPreferences settings = context.getApplicationContext().getSharedPreferences(Constants.USER_DETAILS, 0);
request.setPlayerId(BigInteger.valueOf((settings.getLong(Constants.USER_DETAILS_PLAYERID, 0))));
request.setSignedInOn(settings.getLong(Constants.USER_DETAILS_SIGNEDINON, 0));
return request;
}
}
My last resort might be to move my server to another location, and see if this could not be related to my broadband router. I have notice that some of my HTTP call do not reach the server as well, though port forwarding is properly in place.
Thanks.
David.

I can't find where in your source code the server sends a message every 10 minutes to all connected clients, but I have experienced connection reset exceptions while using long-lasting WebSocket connections. I solved that problem by making sure some data (ping-pong message) was send from the client every minute.
At the time I traced the problem to my home-router which simply closed all idle connections after 5 minutes, but firewalls can exhibit the same kind of behavior. Neither server or client will notice a closed connection until data is transmitted. This is especially nasty for the client if the client is expecting data from the server - that data will simply never arrive. Therefor, make it the responsibility of the client to check if a connection is still valid (and reconnect when needed).
Since the introduction of the ping-pong message from the client every minute, I have not seen connection reset exceptions.

Having multiple clients connecting to Java Server

I'm creating a simple socket server using Java. I am able to connect one client at a time, I tried to implement Threads to handle multiple client. In my Server constructor I created a thread that handles the ServerSocket, and should keep listening for new clients. Once a socket is connected then I tried to create another thread to handle the client Socket. But I am still not able to connect more than one client. The second client I try to connect will not get IO streams.
public class Server extends JFrame {
private JTextField enterField;
private JTextArea displayArea;
private ObjectOutputStream output;
private ObjectInputStream input;
private ServerSocket server;
private Socket connection;
private int counter = 1;
public Server() {
super("Server");
enterField = new JTextField();
enterField.setEditable(false);
enterField.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent event) {
sendData(event.getActionCommand());
enterField.setText("");
}
});
add(enterField, BorderLayout.NORTH);
displayArea = new JTextArea();
add(new JScrollPane(displayArea));
setSize(300, 150);
setLocation(500, 500);
setVisible(true);
new Thread(new Runnable() {
public void run() {
try {
server = new ServerSocket(50499, 100);
displayMessage("Listening on Port: "
+ server.getLocalPort() + "\n");
for (;;) {
Socket nextClient = server.accept();
displayMessage("Client Connected");
new ClientThread(nextClient).start();
nextClient = null;
}
} catch (IOException exception) {
exception.printStackTrace();
}
}
}).start();
}
private void closeConnection() {
displayMessage("\nTerminating connection\n");
setTextFieldEditable(false);
try {
output.close();
input.close();
connection.close();
} catch (IOException ioException) {
ioException.printStackTrace();
}
}
private void displayMessage(final String string) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
displayArea.append(string);
}
});
}
private void setTextFieldEditable(final boolean editable) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
enterField.setEditable(editable);
}
});
}
private void sendData(String message) {
try {
output.writeObject("SERVER>>> " + message);
output.flush();
displayMessage("\nSERVER>>> " + message);
} catch (IOException ioException) {
displayArea.append("\nError Writing Object");
}
}
private class ClientThread extends Thread {
public ClientThread(Socket socket) throws IOException {
try {
connection = socket;
output = new ObjectOutputStream(socket.getOutputStream());
output.flush();
input = new ObjectInputStream(socket.getInputStream());
displayMessage("Got I/O Stream\n");
displayMessage("Connection " + counter + " received from: "
+
connection.getInetAddress().getHostName());
counter++;
String message = "Connection Sucessful";
sendData(message);
setTextFieldEditable(true);
do {
message = (String) input.readObject();
displayMessage("\n" + message);
} while (!message.endsWith(">>> TERMINATE"));
} catch (ClassNotFoundException classNotFoundException) {
displayMessage("\nUnknown object type recieved");
} finally {
closeConnection();
}
}
}
}

You're doing the connection stuff inside the ClientThread constructor. Therefore the new ClientThread(...) never returns until you send a TERMINATEcommand. Put the logic inside the run() method.
private class ClientThread extends Thread {
private Socket socket;
// The queue, thread-safe for good measure
private Queue<String> queue = new ConcurrentLinkedQueue<String>();
public ClientThread(Socket socket) throws IOException {
this.socket = socket;
}
public void send(String message) {
if (message != null) {
this.sendQueue.add(message);
}
}
public void run() {
try {
connection = socket;
output = new ObjectOutputStream(socket.getOutputStream());
output.flush();
input = new ObjectInputStream(socket.getInputStream());
displayMessage("Got I/O Stream\n");
displayMessage("Connection " + counter + " received from: "
+ connection.getInetAddress().getHostName());
counter++;
String message = "Connection Sucessful";
sendData(message);
setTextFieldEditable(true);
do {
// Purge the queue and send all messages.
while ((String msg = queue.poll()) != null) {
sendData(msg);
}
message = (String) input.readObject();
displayMessage("\n" + message);
} while (!message.endsWith(">>> TERMINATE"));
} catch (ClassNotFoundException classNotFoundException) {
displayMessage("\nUnknown object type recieved");
} finally {
closeConnection();
}
}
}
Tipically, you'll send messages to the connection from other threads:
ClientThread client = new ClientThread(newClient);
client.start();
client.send("Hi there");
Personally, I would have used a non-blocking (NIO) networking library such as Netty or Mina to implement this sort of stuff. There's some learning to do to use them but I think its worth it. Non-blocking means that you don't dedicate a separate thread for each connection but rather you're notified when something is received in the socket.

You did not provide implementation of run method for Thread Class.
Put processing logic of ClientThread inside run method
To keep your code modularised and more manageable make your ClientThread class public and share only necessary resources between those thread.
public class ClientThread extends Thread { //make class public
private Socket socket;
// define all other references
ObjectOutputStream output = null;
//...
public ClientThread(Socket socket) throws IOException {
this.socket = socket;
}
public void run() {
try {
connection = socket;
output = new ObjectOutputStream(socket.getOutputStream());
output.flush();
input = new ObjectInputStream(socket.getInputStream());
displayMessage("Got I/O Stream\n");
displayMessage("Connection " + counter + " received from: "
+
connection.getInetAddress().getHostName());
counter++;
String message = "Connection Sucessful";
sendData(message);
setTextFieldEditable(true);
do {
message = (String) input.readObject();
displayMessage("\n" + message);
} while (!message.endsWith(">>> TERMINATE"));
} catch (ClassNotFoundException classNotFoundException) {
displayMessage("\nUnknown object type recieved");
} finally {
closeConnection();
}
}
}}

Chat Application using socket not working over Internet in Java

I am currently developing chat application working over Internet.currently my application working fine over LAN but not working over Internet.I have also used port forwarding.I have done setting in modem and forward the port to private IP address but still it's not working.I got the error that "server isn't found".Please suggest me what I have to do and tell,Am I done the correct setting in modem or not??
Below is my server code...
Server.java
import java.util.*;
import java.net.*;
import java.io.*;
class Server implements ChatConstants
{
private static Vector list;
private ServerSocket ssocket ;
private Service service;
private static Socket socket;
private boolean done=false;
private static Hashtable userTable = new Hashtable();
private static Hashtable _userList = new Hashtable();
private static Hashtable _conflist = new Hashtable();
public Server() throws UnknownHostException
{
System.out.println("Initializing...");
list=new Vector(BACKLOG);
try {
ssocket= new ServerSocket(SERVER_PORT,BACKLOG);
}
catch(Exception e) {
e.printStackTrace();
System.out.println("Inside constructor"+e);
}
start();
}
public void start() throws UnknownHostException
{
byte[] data;
int header;
Socket _socket = null;
String hostname = null;
System.out.println("Server successfully started at "
+InetAddress.getLocalHost().toString()
+" port "+SERVER_PORT);
while(!done) {
try
{
_socket=ssocket.accept();
if(_socket != null) {
synchronized(list) {
list.addElement(_socket);
}
DataInputStream dis=new DataInputStream(_socket.getInputStream());
data = new byte[MAX_MESSAGE_SIZE];
dis.read(data);
Message message = ((Message)ChatUtils.bytesToObject(data));
System.out.println("Joined client "
+message._username+" at "+message._host+"...");
synchronized(userTable) {
userTable.put(message._username,_socket);
}
addUser(message);
sendUserList(message);
writeToClients(message);
service = new Service(_socket,hostname,message._user);
}
}
catch(Exception e) {
e.printStackTrace();
System.out.println("Thread exception"+e);
try {
_socket.close();
}
catch(Exception ex) {
ex.printStackTrace();
System.out.println("ERROR CLOSING SOCKET");
}
}
}//END WHILE
}
private void addUser(Message message)
{
synchronized(_userList) {
_userList.put(message._user.toString(),message._user);
}
}
public static void updateUser(User user)
{
User myuser;
synchronized(_userList) {
_userList.put(user.toString(),user);
}
}
public static synchronized void writeToClients(Message message)
{
byte[] data;
DataOutputStream dos;
for(int count=0;count<list.size();count++) {
try {
dos=new
DataOutputStream(((Socket)list.elementAt(count)).getOutputStream());
data=ChatUtils.objectToBytes(message);
dos.write(data,0,data.length);
}
catch(Exception e) {
e.printStackTrace();
System.out.println("Output exception");
}
}//END FOR
}
public static void writeToClient(Message message)
{
Socket socket;
byte[] data;
DataOutputStream dos;
synchronized(userTable) {
try {
socket = (Socket)userTable.get(message._destination);
dos=new DataOutputStream(socket.getOutputStream());
data=ChatUtils.objectToBytes(message);
dos.write(data,0,data.length);
}
catch(Exception e) {
e.printStackTrace();
System.out.println("SEND EXCEPTION"+e);
}
}
}
public static void sendConferenceListToClient(Message message)
{
Socket socket;
byte[] data;
DataOutputStream dos;
synchronized(userTable) {
try {
Message mymessage= new Message(CONFERENCE_LIST);
Vector vector = (Vector)
_conflist.get(message._destination);
mymessage._username = message._username;
mymessage._destination = message._destination;
mymessage.userlist = vector;
socket = (Socket)userTable.get(message._username);
if(socket!=null) {
dos=new DataOutputStream(socket.getOutputStream());
data=ChatUtils.objectToBytes(mymessage);
dos.write(data,0,data.length);
}
}
catch(Exception e) {
e.printStackTrace();
System.out.println("CONFERENCE LIST EXCEPTION"+e);
}
}
}
public static void writeToPublicChat(Message message)
{
Socket socket;
byte[] data;
DataOutputStream dos;
synchronized(_conflist) {
try {
Vector svector = (Vector)_conflist.get(message._destination);
for(int cnt=0;cnt<svector.size();cnt++) {
synchronized(userTable) {
try {
socket = (Socket)userTable.get((svector.get(cnt).toString()));
if(socket!=null) {
dos=new DataOutputStream(socket.getOutputStream());
data=ChatUtils.objectToBytes(message);
dos.write(data,0,data.length);
}
}
catch(Exception e) {
e.printStackTrace();
System.out.println("PUBLIC CHAT EXCEPTION"+e);
}
}
}
} catch(Exception e){
e.printStackTrace();
System.out.println("PUBLIC EXCEPTION"+e);
}
}
}
public static void inviteToPublicChat(Vector svector,Message message)
{
Socket socket;
byte[] data;
DataOutputStream dos;
synchronized(_conflist) {
for(int cnt=0;cnt<svector.size();cnt++) {
synchronized(userTable) {
try {
socket = (Socket)userTable.get((svector.get(cnt).toString()));
if(socket != null) {
dos=new DataOutputStream(socket.getOutputStream());
data=ChatUtils.objectToBytes(message);
dos.write(data,0,data.length);
}
}
catch(Exception e) {
e.printStackTrace();
System.out.println("PUBLIC INVITE EXCEPTION"+e);
}
}
}
}
}
private void sendUserList(Message message)
{
int header=0;
String destination;
header=message._header;
destination = message._destination;
message._header = USERS_LIST;
message._destination = message._username;
message.userlist = new Vector(_userList.values());
writeToClient(message);
//Restore the headers
message._destination = destination;
message._header = header;
}
public static synchronized void removeUser(User user)
{
try {
Socket socket = (Socket)userTable.get(user.toString());
list.removeElement(socket);
_userList.remove(user.toString());
userTable.remove(user.toString());
}
catch(Exception e) {
e.printStackTrace();
System.out.println("ERROR REMOVING SOCKET "+e);
}
}
public static synchronized void processClientMessage(Message message)
{
switch(message._header) {
case CHANGE_STATUS:
updateUser(message._user);
writeToClients(message);
break;
case CLIENT_LOGOUT:
removeUser(message._user);
writeToClients(message);
break;
case CONFERENCE_CREATE:
Vector myvector = new Vector();
myvector.add(message._username);
_conflist.put(message._user.toString(),myvector);
case CONFERENCE_INVITE:
inviteToPublicChat(message.userlist,message);
break;
case CONFERENCE_JOIN:
Vector vector=null;
vector = (Vector)
_conflist.get(message._destination.toString());
vector.add(message._username);
_conflist.put(message._destination.toString(),vector);
writeToPublicChat(message);
break;
case CONFERENCE_DENY:
//_conflist.remove(message._user.toString(),message.userlist);
writeToPublicChat(message);
break;
case CONFERENCE_LEAVE:
Vector vectors =(Vector)
_conflist.get(message._destination.toString());
for(int count=0;count<vectors.size();count++) {
if(message._username.equals((vectors.elementAt(count).toString())))
vectors.remove(count);
}
if(vectors.size() != 0)
_conflist.put(message._user.toString(),vectors);
else//IF THERE ARE NO MORE USERS
_conflist.remove(message._user.toString());//DONE CONFERENCE
writeToPublicChat(message);
break;
case PUBLIC_CHAT:
writeToPublicChat(message);
break;
case CONFERENCE_LIST:
sendConferenceListToClient(message);
break;
default:
writeToClient(message);
}
}
public static void main(String args[]) throws Exception
{
Server chatserver=new Server();
}
}
//
// Service: Service class for each clients connected to server.
//
class Service implements Runnable, ChatConstants
{
private DataInputStream dis;
private Socket socket;
private boolean done=false;
private Thread thread;
private String hostname;
private User user;
public Service(Socket _socket,String _hostname,User user)
{
try {
this.socket = _socket;
this.hostname=_hostname;
this.user = user;
dis=new DataInputStream(socket.getInputStream());
thread=new Thread(this,"SERVICE");
thread.start();
}
catch(Exception e){
e.printStackTrace();
System.out.println("service constructor"+e);
}
}
public void run()
{
byte[] data;
while(!done)
{
try {
data = new byte[MAX_MESSAGE_SIZE];
dis.read(data);
Message message = ((Message)ChatUtils.bytesToObject(data));
Server.processClientMessage(message);
}
catch(Exception e) {
e.printStackTrace();
done = true;
Server.removeUser(user);
Message message = new Message(CLIENT_LOGOUT);
user.isOnline = OFFLINE;
message._user = user;
Server.writeToClients(message);
try {
socket.close();
} catch(Exception se) {
se.printStackTrace();
System.out.println("ERROR CLOSING SOCKET "+se);
}
//System.out.println("SERVICE THREAD EXCEPTION"+e);
}
}//END WHILE
}
}
Thanks in advance.

I think the
ssocket= new ServerSocket(SERVER_PORT,BACKLOG);
is making the issue. Use the version
ssocket= new ServerSocket(SERVER_PORT,BACKLOG,LOCAL_INET_ADDRESS);
and bind server to some constant local IP. Now use the port forwarding in the modem, to forward all requests to that local ip. Make sure that the firewall is not preventing you to use the port. Since firewall may allow a local networking but not to web.