Sample TCP server

Server.java

import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.net.*;
import java.util.*;
import java.nio.charset.*;

public class Server {

    public Selector sel = null;
    public ServerSocketChannel server = null;
    public SocketChannel socket = null;
    public int port = 4900;
    String result = null;

    public Server() {
        System.out.println("Inside default ctor");
    }

    public Server(int port) {
        System.out.println("Inside the other ctor");
        this.port = port;
    }

    public void initializeOperations() throws IOException, UnknownHostException {
        System.out.println("Inside initialization");
        sel = Selector.open();
        server = ServerSocketChannel.open();
        server.configureBlocking(false);
        InetAddress ia = InetAddress.getLocalHost();
        InetSocketAddress isa = new InetSocketAddress(ia, port);
        server.socket().bind(isa);
    }

    public void startServer() throws IOException {
        System.out.println("Inside startserver");
        initializeOperations();
        System.out.println("Abt to block on select()");
        SelectionKey acceptKey = server.register(sel, SelectionKey.OP_ACCEPT);

        while (acceptKey.selector().select() > 0) {

            Set readyKeys = sel.selectedKeys();
            Iterator it = readyKeys.iterator();

            while (it.hasNext()) {
                SelectionKey key = (SelectionKey) it.next();
                it.remove();

                if (key.isAcceptable()) {
                    System.out.println("Key is Acceptable");
                    ServerSocketChannel ssc = (ServerSocketChannel) key.channel();
                    socket = (SocketChannel) ssc.accept();
                    socket.configureBlocking(false);
                    SelectionKey another = socket.register(sel, SelectionKey.OP_READ | SelectionKey.OP_WRITE);
                }
                if (key.isReadable()) {
                    System.out.println("Key is readable");
                    String ret = readMessage(key);
                    if (ret.length() > 0) {
                        writeMessage(socket, ret);
                    }
                }
                if (key.isWritable()) {
                    System.out.println("THe key is writable");
                    String ret = readMessage(key);
                    socket = (SocketChannel) key.channel();
                    if (result.length() > 0) {
                        writeMessage(socket, ret);
                    }
                }
            }
        }
    }

    public void writeMessage(SocketChannel socket, String ret) {
        System.out.println("Inside the loop");

        if (ret.equals("quit") || ret.equals("shutdown")) {
            return;
        }
        File file = new File(ret);
        try {

            RandomAccessFile rdm = new RandomAccessFile(file, "r");
            FileChannel fc = rdm.getChannel();
            ByteBuffer buffer = ByteBuffer.allocate(1024);
            fc.read(buffer);
            buffer.flip();

            Charset set = Charset.forName("UTF-8");
            CharsetDecoder dec = set.newDecoder();
            CharBuffer charBuf = dec.decode(buffer);
            System.out.println(charBuf.toString());
            buffer = ByteBuffer.wrap((charBuf.toString()).getBytes());
            int nBytes = socket.write(buffer);
            System.out.println("nBytes = " + nBytes);
            result = null;
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    public String readMessage(SelectionKey key) {
        int nBytes = 0;
        socket = (SocketChannel) key.channel();
        ByteBuffer buf = ByteBuffer.allocate(1024);
        try {
            nBytes = socket.read(buf);
            buf.flip();
            Charset charset = Charset.forName("UTF-8");
            CharsetDecoder decoder = charset.newDecoder();
            CharBuffer charBuffer = decoder.decode(buf);
            result = charBuffer.toString();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;
    }

    public static void main(String args[]) {
        Server server = new Server();
        try {
            server.startServer();
        } catch (IOException e) {
            e.printStackTrace();
            System.exit(-1);
        }

    }
}