一、基於Nio的 Server ,過程略複雜，但是無疑這樣的效率高；程式碼中得註釋比較詳細，請看註釋說明

package com.zhuoxuan.net.nio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
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.Iterator;
import java.util.Random;
import java.util.Set;

/**
 * 
 * <p>
 * 	基於nio的Server
 * </p>
 * 
 * @author 卓軒
 * @建立時間：2014年7月7日
 * @version： V1.0
 */
public class NioServer {
	
	private final int port = 8787;
	private final int BLOCK_SIZE = 4096;
	
	private Selector selector;
	
	private ByteBuffer receiveBuffer = ByteBuffer.allocate(BLOCK_SIZE);
	private ByteBuffer sendBuffer = ByteBuffer.allocate(BLOCK_SIZE);
	
	
	

	//建構函式
	public NioServer() throws IOException {
		//開啟伺服器套接字通道 
		ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
		//伺服器配置為非阻塞模式
		serverSocketChannel.configureBlocking(false);
		//獲取與通道關聯的 ServerSocket物件
		ServerSocket serverSocket = serverSocketChannel.socket();
		//繫結埠
		serverSocket.bind(new InetSocketAddress(port));
		//開啟一個選擇器
		selector = Selector.open();
		//註冊到selector上，等待連線
		serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
		
		System.out.println("Server:init successfuly.");
	}
	
	/**
	 * 監聽埠
	 */
	private void linstenr() throws Exception{
		
		while (true) {
			//選擇一組鍵
			selector.select();
			//返回獲取選擇的鍵集
			Set<SelectionKey> selectionKeys = selector.selectedKeys();
			if(selectionKeys.isEmpty()){
				continue;
			}
			//遍歷，迴圈處理請求的鍵集
			Iterator<SelectionKey> iterator =  selectionKeys.iterator();
			while (iterator.hasNext()) {
				SelectionKey selectionKey = (SelectionKey) iterator.next();
				iterator.remove();
				handlerKey(selectionKey);
			}
			
			Thread.sleep(4000);
		}
		
	}
	
	/**
	 * 處理對應的  SelectionKey
	 * @param selectionKey
	 */
	private void handlerKey(SelectionKey selectionKey) throws IOException{
		
		ServerSocketChannel server;
		SocketChannel client;
		
		// 測試此鍵的通道是否已準備好接受新的套接字連線
		if(selectionKey.isAcceptable()){
			//此鍵對應的關聯通道
			server = (ServerSocketChannel)selectionKey.channel();
			//接受到此通道套接字的連線
			client = server.accept();
			//配置為非阻塞
			client.configureBlocking(false);
			//註冊到selector 等待連線
			client.register(selector, SelectionKey.OP_READ);
			
		}
		
		else if (selectionKey.isReadable()) {
		
			client = (SocketChannel)selectionKey.channel();
			//將緩衝區清空，下面讀取
			receiveBuffer.clear();
			//將客戶端傳送來的資料讀取到 buffer中
			int count = client.read(receiveBuffer);
			if(count >0){
				String receiveMessage = new String(receiveBuffer.array(),0,count);
				System.out.println("Server:接受客戶端的資料:" + receiveMessage);
				client.register(selector, SelectionKey.OP_WRITE);
			}
		}
		
		else if (selectionKey.isWritable()) {
			//傳送訊息buffer 清空
			sendBuffer.clear();
			//返回該鍵對應的通道
			client = (SocketChannel)selectionKey.channel();
			String sendMessage = "Send form Server...Hello... "+new Random().nextInt(100)+" .";
			//向緩衝區中寫入資料
			sendBuffer.put(sendMessage.getBytes());
			//put了資料，標誌位被改變
			sendBuffer.flip();
			//資料輸出到通道
			client.write(sendBuffer);
			System.out.println("Server:伺服器向客戶端傳送資料:" + sendMessage);
			client.register(selector, SelectionKey.OP_READ);
		}
		
		
	}
	
	
	public static void main(String[] args) {
		
		try {
			
			NioServer nioServer = new NioServer();
			nioServer.linstenr();
			
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		
	}
	

}
 

package com.zhuoxuan.net.nio;

import java.net.InetSocketAddress;
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;

/**
 * 
 * <p>
 *   nio client
 * </p>
 * 
 * @author 卓軒
 * @建立時間：2014年7月7日
 * @version： V1.0
 */
public class NioClient {

	private static final int BLOCK_SIZE = 4096;
	
	private static ByteBuffer sendBuffer = ByteBuffer.allocate(BLOCK_SIZE);
	
	private static ByteBuffer receiveBuffer = ByteBuffer.allocate(BLOCK_SIZE);
	
	private static final  InetSocketAddress SERVER_ADDRESS = new InetSocketAddress("127.0.0.1",8787);
	
	
	public static void main(String[] args) {
		
		try {
			//開啟socket通道
			SocketChannel socketChannel = SocketChannel.open();
			//設定為非阻塞模式
			socketChannel.configureBlocking(false);
			//開啟選擇器
			Selector selector = Selector.open();
			//向selector 選擇器註冊此通道
			socketChannel.register(selector, SelectionKey.OP_CONNECT);
			//連結
			socketChannel.connect(SERVER_ADDRESS);
			
			SocketChannel client;
			while (true) {
				//選擇一組鍵
				selector.select();
				//返回此選擇器的已選擇鍵集
				Set<SelectionKey> selectionKeys = selector.selectedKeys();
				Iterator<SelectionKey> iterator = selectionKeys.iterator();
				//遍歷對應的 SelectionKey 處理
				while (iterator.hasNext()) {
					SelectionKey selectionKey = (SelectionKey) iterator.next();
					//判斷此鍵的通道是否已完成其套接字連線操作
					if (selectionKey.isConnectable()) {
						System.out.println("Client:  already connected.");
						client = (SocketChannel)selectionKey.channel();
						//判斷該通道是否進行連線過程、完成連線過程
						if(client.isConnectionPending()){
							client.finishConnect();
							
							sendBuffer.clear();
							sendBuffer.put("hello nio server".getBytes());
							sendBuffer.flip();
							
							client.write(sendBuffer); //將資料寫入該通道
							client.register(selector, SelectionKey.OP_READ);
						}
					}
					else if(selectionKey.isReadable()){
						//獲取該鍵中對應的通道
						client = (SocketChannel)selectionKey.channel();
						
						receiveBuffer.clear();
						int count = client.read(receiveBuffer);
						if(count > 0){
							String receiveMessage = new String(receiveBuffer.array(),0,count);
							System.out.println("Client：接收到來自Server的訊息，" + receiveMessage);
							client.register(selector, SelectionKey.OP_WRITE);
						}
					}
					else if(selectionKey.isWritable()){
						sendBuffer.clear();  
	                    client = (SocketChannel) selectionKey.channel();  
	                    String sendText = "hello server,key..";
	                    sendBuffer.put(sendText.getBytes());  
	                     //將緩衝區各標誌復位,因為向裡面put了資料標誌被改變要想從中讀取資料發向伺服器,就要復位  
	                    sendBuffer.flip();  
	                    client.write(sendBuffer);  
	                    System.out.println("Client:客戶端向伺服器端傳送資料--："+sendText);  
	                    client.register(selector, SelectionKey.OP_READ);
						
					}
				}
				selectionKeys.clear();
				Thread.sleep(3000);
			}
			
			
			
			
			
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		
	}
	
	
	
}