public class Server {
    private ServerSocket serverSocket = null;
    private Socket clientSocket = null;

    public Server() {
        try {
            serverSocket = new ServerSocket(7003);
        } catch (IOException e) {
            System.err.println("Could not listen on port: 7003");
            System.exit(1);
        }

        try {
            clientSocket = serverSocket.accept();
        } catch (IOException e) {
            System.err.println("Accept failed");
            System.exit(1);
        }
    }

    public void startServer() throws IOException {
        PrintWriter output = new PrintWriter(clientSocket.getOutputStream(), true);
        BufferedReader input = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));

        String inputLine, outputLine;

        outputLine = "Connected to Server";
        output.println(outputLine);

        while ((inputLine = input.readLine()) != null) {
            // This just determines users input and server ruturns output based on that

            outputLine = this.getServerOutput(inputLine);
            output.println(outputLine);

            if (outputLine.equals("Bye"))
                break;
        }

        output.close();
        input.close();
        clientSocket.close();
        serverSocket.close();
    }
}

public Server()
{
    try
    {
        serverSocket = new ServerSocket(7003);
    }
    catch (IOException e)
    {
        System.err.println("Could not listen on port: 7003");
        System.exit(1);
    }

    try
    {
        while(true) {
            final Socket socket = serverSocket.accept();
            new Thread(new Runnable() {
                public void run() {
                    try {
                        startServer(socket);
                    } catch(IOException e) {e.printStackTrace();}
                }
            }).start();
        }
    }
    catch(IOException e)
    {
        System.err.println("Accept failed");
        System.exit(1);
    }
}

clientSocket = serverSocket.accept();

public void startServer() throws IOException {
    PrintWriter output = new PrintWriter(clientSocket.getOutputStream(), true);
    ...

public class Server {
    private ServerSocket serverSocket = null;

    public Server(int portNumber) throws IOException {
        serverSocket = new ServerSocket(portNumber);
    }

    // this could be run in a thread in the background
    public void acceptClients() throws IOException {
        // create an open ended thread-pool
        ExecutorService threadPool = Executors.newCachedThreadPool();
        try {
            while (!Thread.currentThread().isInterrupted()) {
                // wait for a client to connect
                Socket clientSocket = serverSocket.accept();
                // create a new client handler object for that socket,
                // and fork it in a background thread
                threadPool.submit(new ClientHandler(clientSocket));
            }
        } finally {
            // we _have_ to shutdown the thread-pool when we are done
            threadPool.shutdown();
        }
    }

    // if server is running in background, you stop it by killing the socket
    public void stop() throws IOException {
        serverSocket.close();
    }

    // this class handles each client connection
    private static class ClientHandler implements Runnable {
        private final Socket clientSocket;
        public ClientHandler(Socket clientSocket) {
            this.clientSocket = clientSocket;
        }
        public void run() {
            // use the client socket to handle the client connection
            ...
        }
    }
}

public void acceptClients() throws IOException {
        while (!Thread.currentThread().isInterrupted()) {
            // wait for a client to connect
            Socket clientSocket = serverSocket.accept();
            // fork a background client thread
            new Thread(new ClientHandler(clientSocket)).start();
        }
    }

public class MyServer {

    private static MyServer server;
    private ServerSocket serverSocket;

    /**
     * This executor service has 10 threads.
     * So it means your server can process max 10 concurrent requests.
     */
    private ExecutorService executorService = Executors.newFixedThreadPool(10);

    public static void main(String[] args) throws IOException {
        server = new MyServer();
        server.runServer();
    }

    private void runServer() {
        int serverPort = 8085;
        try {
            System.out.println("Starting Server");
            serverSocket = new ServerSocket(serverPort);

            while(true) {
                System.out.println("Waiting for request");
                try {
                    Socket s = serverSocket.accept();
                    System.out.println("Processing request");
                    executorService.submit(new ServiceRequest(s));
                } catch(IOException ioe) {
                    System.out.println("Error accepting connection");
                    ioe.printStackTrace();
                }
            }
        }catch(IOException e) {
            System.out.println("Error starting Server on "+serverPort);
            e.printStackTrace();
        }
    }

    //Call the method when you want to stop your server
    private void stopServer() {
        //Stop the executor service.
        executorService.shutdownNow();
        try {
            //Stop accepting requests.
            serverSocket.close();
        } catch (IOException e) {
            System.out.println("Error in server shutdown");
            e.printStackTrace();
        }
        System.exit(0);
    }

    class ServiceRequest implements Runnable {

        private Socket socket;

        public ServiceRequest(Socket connection) {
            this.socket = connection;
        }

        public void run() {

            //Do your logic here. You have the `socket` available to read/write data.

            //Make sure to close
            try {
                socket.close();
            }catch(IOException ioe) {
                System.out.println("Error closing client connection");
            }
        }
    }
}