Оперативни Системи Лабс 2-4 Chat Room

//СЕРВЕР СТРАНА, КЛИЕНТ ПОДОЛЕ

package labs2.com;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.ConcurrentHashMap;

public class TCPServer {

    private ServerSocket server;
    private static ConcurrentHashMap<Integer, Socket> activeConnections;

    class ServerWorkerThread extends Thread {
        Socket client;
        DataInputStream reader;

        ServerWorkerThread(Socket client) throws IOException {
            this.client = client;
            reader = new DataInputStream(client.getInputStream());
        }

        @Override
        public void run() {
            // todo: Handle listening to messages
            String line = null;
            try {
                while (!(line = reader.readUTF()).isEmpty()) {
                    if(line.startsWith("END:")) {
                        // izvadi go END: od porakata za da se dobie ID-to
                        endConnection(Integer.parseInt(line.substring(4)));
                    }else {
                        String[] split = line.split(":");
                        String targetSubstring = split[split.length - 1];
                        Integer target = Integer.parseInt(targetSubstring);
                        // izvadi go Id-to od krajot na porakta + 1 za dvete tocki
                        String message = line.substring(0, line.length() - (targetSubstring.length() + 1));
                        // pisi na target-ot so dataoutputstream
                        new DataOutputStream(getConnection(target).getOutputStream()).writeUTF(message);
                    }
                }
            }catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    // todo: Get the required connection
    public Socket getConnection(int id) {
        return activeConnections.get(id);
    }

    // todo: Add connected client to the hash map
    void addConnection(int id, Socket connection) {
        activeConnections.put(id, connection);
    }

    synchronized void endConnection(int id){
        activeConnections.remove(id);
    }

    //todo: Initialize server
    TCPServer(int port) throws IOException {
        server = new ServerSocket(port);
    }

    // todo: Handle server listening
    // todo: For each connection, start a separate
    // todo: thread (ServerWorkerThread) to handle the communication
    void listen() throws IOException {
        Socket client;
        while(true) {
            client = server.accept();
            String firstMessage = new DataInputStream(client.getInputStream()).readUTF();
            // Izvadi go CONNECT: od prvata poraka za da se dobie id-to
            addConnection(Integer.parseInt(firstMessage.substring(8)), client);
            ServerWorkerThread workerThread = new ServerWorkerThread(client);
            workerThread.start();
        }
    }

    public static void main(String[] args) throws IOException {
        // todo: Start server
        activeConnections = new ConcurrentHashMap<>();
        TCPServer serverSocket = new TCPServer(8080);
        serverSocket.listen();
    }
}

// КЛИЕНТ

package labs2.com;

import java.io.*;
import java.net.Socket;

class ClientStarterWorkerThread extends Thread {

    private int ID;
    private DataInputStream inputStream;

    public ClientStarterWorkerThread(int clientID, DataInputStream inputStream) {
        this.ID = clientID;
        this.inputStream = inputStream;
    }

    @Override
    public void run() {
        // todo: Handle listening to messages
        String line = null;
        try {
            while ((line = inputStream.readUTF()) != null) {
                System.out.println("Client " + ID + " has received message: " + line);
            }
        }catch (IOException e) {
            e.printStackTrace();
        }
    }
}

public class ClientStarer {

    private int ID;
    Socket socket;
    DataOutputStream writer;
    DataInputStream inputStream;

    private ClientStarer(int id, String host, int port) throws IOException {
        this.ID = id;
        // todo: Connect to server and send client ID
        socket = new Socket(host, port);
        writer = new DataOutputStream(socket.getOutputStream());
        inputStream = new DataInputStream(socket.getInputStream());

        writer.writeUTF("CONNECT:"+id);
        listen();
    }

    void sendMessage(int idReceiver, String message) throws IOException {
        writer.writeUTF(message + ":" + idReceiver);
    }

    // todo: end communication - send END to server
    private void endCommunication() throws IOException {
        writer.writeUTF("END:"+ID);
    }

    private void listen() {
        ClientStarterWorkerThread clientStarterWorkerThread = new ClientStarterWorkerThread(ID, inputStream);
        clientStarterWorkerThread.start();
    }

    public static void main(String[] args) throws IOException, InterruptedException {
        ClientStarer client1 = new ClientStarer(1, "localhost", 8080);
        ClientStarer client2 = new ClientStarer(2, "localhost", 8080);
        ClientStarer client3 = new ClientStarer(3, "localhost", 8080);

        // Simulate chat
        client1.sendMessage(2, "Hello from client 1");
        Thread.sleep(1000);
        client2.sendMessage(3, "Hello from client 2");
        Thread.sleep(1000);
        client1.sendMessage(3, "Hello from client 1");
        Thread.sleep(1000);
        client3.sendMessage(1, "Hello from client 3");
        Thread.sleep(1000);
        client3.sendMessage(2, "Hello from client 3");

        // Exit the chatroom
        client1.endCommunication();
        client2.endCommunication();
        client3.endCommunication();
    }
}