Java NIO tcp tunnel

tcptunnel.java

package ctptunnel;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class NioProxy {
	
	// mappa client remoto - server remoto
	private Map<SocketChannel, SocketChannel> proxy = new HashMap<SocketChannel, SocketChannel>();
	private static final int BYTE_BUFFER_SIZE = 8192;
	
	public void serve() {
		
		try {
			
			Selector serverSelector = Selector.open();
			Selector remoteSelector = Selector.open();
			
			ServerSocketChannel sChannel = ServerSocketChannel.open();
			sChannel.configureBlocking(false);
			sChannel.socket().bind(new InetSocketAddress(9090));
			
			sChannel.register(serverSelector, SelectionKey.OP_ACCEPT);
			while (true) {
				if (serverSelector.select(1) > 0) {
					Iterator<SelectionKey> iter = serverSelector.selectedKeys().iterator();
					while (iter.hasNext()) {
						SelectionKey key = iter.next();
						iter.remove();
						
						if (key.isValid() && key.isAcceptable()) {
							SocketChannel sc = sChannel.accept();
							sc.configureBlocking(false);
							sc.finishConnect();
							System.out.println("Accept remote connection from " + sc.socket().getRemoteSocketAddress().toString());							
							
							//apro connessione verso sistema esterno
							try {
								SocketChannel forwardTo = SocketChannel.open(new InetSocketAddress("localhost", 2080));
								forwardTo.configureBlocking(false);
								forwardTo.finishConnect();
								forwardTo.register(remoteSelector, SelectionKey.OP_READ);
								proxy.put(sc, forwardTo);	
							} catch (IOException e) {
								System.out.println("Errore connessione remota");								
								sc.close();
								break;
							}							
													
							sc.register(serverSelector, SelectionKey.OP_READ);
							key.interestOps(SelectionKey.OP_ACCEPT);	
							
							
						}					
						if (key.isValid() && key.isReadable()) {							
							SocketChannel remote = (SocketChannel) key.channel();
							
							//prendo il canale remoto
							SocketChannel forwardTo = proxy.get(key.channel());							
							ByteBuffer bb = ByteBuffer.allocateDirect(BYTE_BUFFER_SIZE);						
							int read = remote.read(bb);					
																		
							if (read < 0) { // il client si è disconnesso
								forwardTo.close();
								proxy.remove(remote);								
							}
							
							if (read > 0) { //client manda dati
								bb.flip();
								forwardTo.write(bb);														
								remote.register(serverSelector, SelectionKey.OP_READ);										
							}							
						}						
					}
				}
				if (remoteSelector.select(1) > 0) {
					Iterator<SelectionKey> iter = remoteSelector.selectedKeys().iterator();
					while (iter.hasNext()) {
						SelectionKey key = iter.next();
						iter.remove();
												
						if (key.isValid() && key.isReadable()) { // leggo dal server remoto
							ByteBuffer bb = ByteBuffer.allocateDirect(BYTE_BUFFER_SIZE);		
							SocketChannel forwardTo = (SocketChannel) key.channel();
							int read = forwardTo.read(bb);
							SocketChannel remoteClient = null;
							for (SocketChannel remoteChannel : proxy.keySet()) {
								if (proxy.get(remoteChannel).equals(forwardTo)){
									remoteClient = remoteChannel;
									if (read > 0) {																		
										bb.flip(); 
										remoteClient.write(bb);
									} else { //server disconnesso
										proxy.remove(remoteClient);
										remoteClient.close();
									}
									break;
								}
							}
							
						}
					}
				}
			}
		} catch (IOException e) {
			e.printStackTrace();		
		}
		
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		new NioProxy().serve();
	}

}

ma un caso d'uso quale può essere?

Combattere la noia lavorativa :) Scherzi a parte questo è il primo step per creare un tunnel ssl efficiente (no threads) da embeddare in un applicazione java laddove nn sia applicabile (semplicità, tempi ridotti etc etc) che un preesistente sistema supporti la cifratura (nel mio caso specifico da http ad https). Nn mi piace reinventare la ruota ma le alternative erano framework con i quali spari ad una formica con un cannone.

ok. la mia curiosità era sulla casistica d'utilizzo, ossia: quand'è che un client non può parlare direttamente con un server in SSL , ma deve passare per il tunnel?