import java.nio.ByteBuffer;

import java.nio.channels.ServerSocketChannel;

import java.nio.channels.SocketChannel;

import java.nio.channels.Selector;

import java.nio.channels.SelectionKey;

import java.net.InetSocketAddress;

import java.util.Set;

import java.util.Date;

import java.util.Iterator;

import java.lang.NumberFormatException;

import java.io.IOException;

public class SelectorServer{

public static final int SERVER_PORT = 9999;

public static final String SERVER_HOST = "localhost";

static ByteBuffer buffer = ByteBuffer.allocateDirect(8);

public static void main(String[] args) throws IOException{

int port = SERVER_PORT;

if(args.length>0){

try{

port = Integer.parseInt(args[0]);

}catch(NumberFormatException nfe){

nfe.printStackTrace();

}

}

ServerSocketChannel ssc = ServerSocketChannel.open();

ssc.bind(new InetSocketAddress(SERVER_HOST, port));

ssc.configureBlocking(false); // must be set unblocking mode to register

Selector selector = Selector.open();

ssc.register(selector, SelectionKey.OP_ACCEPT);

System.out.println("Server starting... listening on port " + port);

while(true){

int n = selector.select(); // perform a blocking selection operation

if(n==0){

System.out.print("*");

continue;

}

System.out.println("select() return value: " + n);

Set<SelectionKey> selectedKeys = selector.selectedKeys();

Iterator<SelectionKey> iter = selectedKeys.iterator();

while(iter.hasNext()){

SelectionKey key = iter.next();

if(key.isAcceptable()){

SocketChannel sc = ((ServerSocketChannel)key.channel()).accept(); // non-blocking mode.

if(sc==null){

System.out.print(".");

continue;

}

System.out.println("Receiving connection");

buffer.clear(); // prepare to new round operation

long currentTime = System.currentTimeMillis();

buffer.putLong(currentTime);

buffer.flip(); // prepare for draining.

System.out.println("Writing current time = " + new Date(currentTime));

while(buffer.hasRemaining()){

sc.write(buffer);

}

System.out.println("Time was written.");

sc.close();

}

iter.remove(); // must remove the key after you finished the channel operation.

}

}

}

}