TCP SERVER

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

public class TCPServer extends Thread {

    private int port;
    private String fileOutput;

    public TCPServer(int port, String fileOutput) {
        this.port = port;
        this.fileOutput = fileOutput;
    }

    @Override
    public void run() {
        System.out.println("TCP is starting...");
        ServerSocket serverSocket = null;

        try {
            serverSocket = new ServerSocket(port);
        } catch (IOException e) {
            System.err.println("Socket Server failed to start.");
            return;
        }
        System.out.println("TCP server is started.");
        System.out.println("Waiting for connections...");
        while (true) {
            Socket socket = null;
            try {
                // CREATE NEW SOCKET AND START WORKER THREAD
                socket = serverSocket.accept();
                // GIVE SOCKET AND FILE OUTPUT PATH TO WORKER THREAD
                new WorkerThread(socket, this.fileOutput).start();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        TCPServer server = new TCPServer(8888, "D:\\data.csv");
        server.start();
    }
}


class WorkerThread extends Thread {
    private Socket socket;
    private String fileOutput;

    public WorkerThread(Socket socket, String fileOutput) {
        this.socket = socket;
        this.fileOutput = fileOutput;
    }

    @Override
    public void run() {
        BufferedReader reader = null;
        PrintWriter writer = null;
        FileWriter fileWriter = null;

        try {
            reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            writer = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()));

            String ipAdress = socket.getInetAddress().toString();
            int port = socket.getPort();

            System.out.printf("Connected:%s:%d\n", ipAdress, port);

            // INITIALLY SEND A HELLO MESSAGE TO CLIENT
            writer.println("HELLO FROM SERVER");
            writer.flush();

            // MAKE THE FILE WRAPPER WITH THE FILE OUTPUT PATH
            File outFile = new File(this.fileOutput);
            if(!outFile.exists()) {
                outFile.createNewFile();
            }

            // AFTER FILE WRAPPER IS CREATED, CREATE A FILE WRITER SO WE CAN WRITE TO THAT FILE
            fileWriter = new FileWriter(outFile);

            String line = null;
            // RECEIVE ALL COMMANDS FROM CLIENT IN LINE VARIABLE IN A LOOP,
            // SO IF CLIENT SENDS MULTIPLE MESSAGES, SERVER RESPONDS TO ALL OF THEM
            while(!(line=reader.readLine()).isEmpty()) {

                // CLOSE CONNECTION IF CLIENT SENDS QUIT COMMAND
                if(line.equals("QUIT")) {
                    System.out.printf("Connection to %s:%d closed\n", ipAdress, port);
                    writer.println("CONNECTION CLOSED BY SERVER");
                    writer.flush();
                    break;
                }

                String[] splitData = line.split(",");
                if (line.contains("HELLO")) {
                    // SEND MESSAGE TO CLIENT ON CLIENT'S HELLO MESSAGE
                    writer.println("SEND DAILY DATA");
                    writer.flush();
                } else if (splitData.length == 3) {
                    // WRITE THE DATA IN THE FILE THAT WE OPENED BEFORE WITH THE FILE WRITER
                    fileWriter.write(line + '\n');
                    fileWriter.flush();
                    writer.println("OK");
                    writer.flush();
                } else {
                    throw new IOException("ERROR NEKOJ AMN");
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (writer != null) {
                writer.close();
            }
            if (socket != null) {
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(fileWriter != null) {
                try {
                    fileWriter.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}