public class ChatServer {
//************************************************************************************
	final int pORT = 4004;
	ServerSocket serverSocket;
	Thread serverThread;
	private volatile Map<String, Socket> clients = new HashMap<String, Socket>();
	BufferedReader usernameGetter;
	BufferedWriter userPresenceNotification;
//************************************************************************************
	public ChatServer() {
		try {
			serverSocket = new ServerSocket(pORT);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
//************************************************************************************
	void connectionsEstablisher(){
		serverThread = Thread.currentThread();
			while(true){
				try {
					Socket connection = serverSocket.accept();
					if(connection != null){
						usernameGetter = new BufferedReader(new InputStreamReader(connection.getInputStream()));
						userPresenceNotification = new BufferedWriter(new OutputStreamWriter(connection.getOutputStream()));
						String connectedClientUsername = usernameGetter.readLine();
						if(checkExistingUser(connectedClientUsername)){
							clients.put(connectedClientUsername, connection);
							Thread connectedSocketThread = new Thread(new SocketHandler(connection));
							connectedSocketThread.setDaemon(true);
							connectedSocketThread.start();
							userPresenceNotification.write("Success"); //dummy command
						} else {
							userPresenceNotification.write("Exists");
						}
					}
					userPresenceNotification.flush();
					usernameGetter.close();
					userPresenceNotification.close();
				} catch (IOException e) {
					e.printStackTrace();
				} 
			}
	}
//************************************************************************************
	public static void main(String[] args) {
		new ChatServer().connectionsEstablisher();

	}
//************************************************************************************
	private class SocketHandler implements Runnable{
		Socket existingSocket;
		BufferedReader existingSocketReader;
		BufferedWriter existingSocketWriter;
		
		SocketHandler(Socket connected){
			existingSocket = connected;
			try {
				existingSocketReader = new BufferedReader(new InputStreamReader(existingSocket.getInputStream(), "UTF-8"));
				existingSocketWriter = new BufferedWriter(new OutputStreamWriter(existingSocket.getOutputStream(), "UTF-8"));
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		
		@Override
		public void run() {
			while(!existingSocket.isClosed()){
				/*/TEST
				try {
					Thread.sleep(2000);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				Set<Entry<String, Socket>> users = clients.entrySet();
				Iterator<Entry<String, Socket>> it = users.iterator();
				while(it.hasNext()){
					Entry<String, Socket> e = it.next();
					System.out.println(e.getKey() + " " + e.getValue());
				}
				//TEST*/
			}
		}
	}
//************************************************************************************
	private boolean checkExistingUser(String username){
		boolean result =true;
			Set<String> alreadyConnectedUsers = clients.keySet();
			for(String s : alreadyConnectedUsers){
				if(s.contentEquals(username)){
					result = false;
					break;
				}
			}
		return result;
	}
//************************************************************************************	
}

public class ChatClient implements Runnable{
//************************************************************************************
	String username;
	Socket toServerConnection;
	final int pORT = 4004; //<- Port
	final String hOST = "127.0.0.1"; // <-Host
	BufferedReader socketReader;
	BufferedWriter socketWriter;
//************************************************************************************
	public void passUsername(String user){
		username = user;
		//System.out.println(username);
	}
//************************************************************************************
	public boolean connectToServer(){
		boolean isConnected = true;
		try {
			toServerConnection = new Socket(hOST, pORT );
			socketReader = new BufferedReader(new InputStreamReader(toServerConnection.getInputStream()));
			socketWriter = new BufferedWriter(new OutputStreamWriter(toServerConnection.getOutputStream()));
			socketWriter.write(username);
			socketWriter.flush();
			if((socketReader.readLine()).contentEquals("Exists")){ // Если заккоментировать этот фрагмент
				isConnected = false;                           // программа работает согласно
			}                                                  // булевому значению установленному изначально.

		} catch (UnknownHostException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return isConnected;
	}
//************************************************************************************	
@Override
public void run() {
	
	
}

}

bConnect.addActionListener(new ActionListener() {
			@Override
			public void actionPerformed(ActionEvent arg0) {
				if((userName = tfUsername.getText()).contentEquals("")){
					JOptionPane.showMessageDialog(ChatWindow.this, "Введи имя пользователя!", "Варнинг!", JOptionPane.WARNING_MESSAGE);
					return;
				}
				clientProgram.passUsername(userName);
				if(clientProgram.connectToServer()){
					tfUsername.setEditable(false);
					bDisconnect.setEnabled(true);
					bSend.setEnabled(true);
					bConnect.setEnabled(false);
					repaint();
				} else {
					JOptionPane.showMessageDialog(ChatWindow.this, "Такой юзер уже чатится!", "Эррор!", JOptionPane.ERROR_MESSAGE);
					return;
				}
			}
		});