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import java.io.IOException;import java.net.InetAddress;import java.net.InetSocketAddress;import java.net.UnknownHostException;import java.nio.ByteBuffer;import java.nio.channels.SelectionKey;import java.nio.channels.Selector;import java.nio.channels.SocketChannel;import java.util.Iterator;import java.util.Set;public class NioClient{	/*研究NIO的各种事件的触发条件*/	private SocketChannel clientChannel = null;	private Selector selector = null;	private InetAddress localAddress = null;	private int localPort = 0;	private InetAddress remoteAddress = null;	private int remotePort = 0;		private Thread task = null;		public NioClient(InetAddress remoteAddress,int remotePort) {		/*初始化本地的地址*/		this.remoteAddress = remoteAddress;		this.remotePort = remotePort;		try {			localAddress = InetAddress.getByName("127.0.0.1");			localPort = 9999; 		} catch (UnknownHostException e) {			// TODO Auto-generated catch block			e.printStackTrace();		}	}		private void initChannel() {		try {			clientChannel = SocketChannel.open();  /*Create and connect*/			clientChannel.configureBlocking(false);			/*注册一个connect事件*/			clientChannel.register(selector, SelectionKey.OP_CONNECT); /*连接将要完成时，或者有错误发生时*/			clientChannel.connect(new InetSocketAddress(remoteAddress, remotePort));		} catch (IOException e) {			// TODO Auto-generated catch block			e.printStackTrace();		}			}		private void initSelector() {		try {			selector = Selector.open();		} catch (IOException e) {			// TODO Auto-generated catch block			e.printStackTrace();		}	}		private void initOperations() {		initSelector();		initChannel();	}		private void startTask() {		Thread task = new Thread(new ClientTask());		task.start();	}		public void launch() {		/*初始化*/		initOperations();		/*启动client的任务线程*/		startTask();	}		private class ClientTask implements Runnable {		Set
   
     okSet = null;		ByteBuffer sendbuffer = ByteBuffer.allocate(256);		ByteBuffer recvbuffer = ByteBuffer.allocate(256);		String echomessage = new String("I am client!");				private void sendEchoRequest(SelectionKey key,ByteBuffer buf) {			/*将数据加入到发送缓存，bytebuffer*/			sendbuffer.clear();			sendbuffer.put(echomessage.getBytes());			sendbuffer.flip();						/*注册writable事件，selector会关注writable事件，一般情况下channel正常状态都是随时可writable的，因为channel与socket一样，是线程安全的，			 * write，read操作应该都是原子操作，且全双工。所以仅当有数据要发送时注册writable事件，否则writable会一直被触发。*/			key.interestOps(SelectionKey.OP_WRITE);		}				private void handleConnectable(SelectionKey key) {			System.out.println("Client:Connectable");			/*收到此事件，表示基于此SocketChannel的连接（TCP）要么有错误发生，要么已经完成*/			SocketChannel client = (SocketChannel)key.channel();						try {				if( client.isConnectionPending() ) {					System.out.println("SocketChannel status:is open="+client.isOpen());					client.finishConnect();  /*如果connect失败，这一步会自动close掉SocketChannel*/										System.out.println("Client:Connection finished successfully!Connect to IP="+((InetSocketAddress)client.getRemoteAddress()).getHostName()+":port="+((InetSocketAddress)client.getRemoteAddress()).getPort());										sendEchoRequest(key,sendbuffer);				} 			} catch (IOException e) {				// TODO Auto-generated catch block				e.printStackTrace();				System.out.println("SocketChannel status:is open="+client.isOpen()+",connection failed!");				/*连接失败，之前的Channel已经被close，这里重新创建一个Channel，重新进行连接。*/				initChannel();			}		}				private void handleWritable(SelectionKey key) {			try {				if( sendbuffer.remaining() > 0 ) {					System.out.println("Client:send to server. msg="+new String(sendbuffer.array(),0,sendbuffer.remaining()));					((SocketChannel)key.channel()).write(sendbuffer);  /*write会改变buffer的position的位置*/					key.interestOps(SelectionKey.OP_READ);				}			} catch (IOException e) {				// TODO Auto-generated catch block				e.printStackTrace();				try {					key.channel().close();					key.cancel();				} catch (IOException e1) {					// TODO Auto-generated catch block					e1.printStackTrace();				}			}		}				private void handleReadable(SelectionKey key) {			try {				recvbuffer.clear();				((SocketChannel)key.channel()).read(recvbuffer);				recvbuffer.flip();								if( recvbuffer.remaining() > 0 ) {					System.out.println("Client:recv echo msg from server="+new String(recvbuffer.array(),0,recvbuffer.remaining()));				}			} catch (IOException e) {				// TODO Auto-generated catch block				e.printStackTrace();				try {					key.channel().close();					key.cancel();				} catch (IOException e1) {					// TODO Auto-generated catch block					e1.printStackTrace();				}			}		}				private void handleSelectionKey(SelectionKey key) {			if( key.isConnectable() ) {				handleConnectable(key);							} else if( key.isReadable() ) {				System.out.println("Client:Readable");				handleReadable(key);			} else if( key.isWritable() ) {				System.out.println("Client:Writable");				handleWritable(key);							} else {				System.out.println("Client:Not handle event="+key.readyOps());			}		}				@Override		public void run() {			// TODO Auto-generated method stub			while(!Thread.currentThread().isInterrupted()) {				try {					int num = selector.select();  /*select will block until something happen*/					if( num > 0 ) {						okSet = selector.selectedKeys();						/*为了简单起见，且只有一个SocketChannel，这里对SelectionKey使用一个循环来处理。如果有多个SocketChannel注册到此						 * Selector，则可能会有多个SocketChannel并发产生事件，这里需要用线程池。*/						Iterator ite = okSet.iterator();						while(ite.hasNext()) {							handleSelectionKey((SelectionKey)ite.next());							ite.remove();  							/*这一步千万不能少，否则select将暂时不响应此channel的这个事件。猜想select会判断某个channel的某个事件在							 * selectedKeySet中是否有事件正在处理（未删除），没有则继续响应，否则暂时屏蔽，直到其被删除。*/						}					}														} catch (IOException e) {					// TODO Auto-generated catch block					e.printStackTrace();				}			}		}			}}/*1、client处理selectedKeys用的是同步方式，不分发线程，因此不会出现同一个channel的readable或writable事件被分发给多个线程的情况； * 2、*/
   

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