采用NIO实现一个Socket服务器

      以前用Socket写服务端，常用的做法是维护一个线程池，每当有客户端连入则交给一个特定的线程处理，处理完之后返回。解除了NIO之后，发现可以不用这样了。使用NIO的话，不需要像以前那样维护线程池了，一个线程就可以搞定多个客户端的请求。

      于是自己就动手写了一个示例程序。

      先描述一下程序：服务端采用ServerSocketChannel，使用Selector注册感兴趣的事件。

                                  测试程序开启连个客户端，与服务器连接并传输内容。服务器接收到消息后，打印出来。  通过结果可以看出NIO的强大。他可以完全胜任这项任务。

                                  虽然这个示例程序的结构有些丑陋，但重点在说明这个奇妙的交互过程。要想采用好的结构可以参见这篇博客：http://www.ibm.com/developerworks/cn/java/l-niosvr/#icomments

                                  本人将本机IP硬编码到程序中了，所以大家下载源码不修改的话会运行不了。

贴出服务端和客户端的代码上来参考一下：

package com.wjy.nioServer;

import java.io.IOException;
import java.net.InetAddress;
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.nio.charset.Charset;
import java.util.Iterator;
import java.util.Set;

public class NIOServer implements Runnable{
	private Selector selector;
	private ServerSocketChannel sscChannel;
	private InetSocketAddress address;
	//private SocketChannel socketChannel;
	private static final int BSIZE=1024;
	
	public NIOServer(int port){
		try {
			selector=Selector.open();
			sscChannel=ServerSocketChannel.open();
			sscChannel.configureBlocking(false);
			address=new InetSocketAddress(InetAddress.getLocalHost(), port);
			ServerSocket serverSocket=sscChannel.socket();
			serverSocket.bind(address);
			sscChannel.register(selector, SelectionKey.OP_ACCEPT);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
	
	@Override
	public void run() {
		// TODO Auto-generated method stub
		while(true){
			try {
				int num=0;
				num=selector.select();
				if(num>0){
					Set selectedKeys=selector.selectedKeys();
					Iterator it=selectedKeys.iterator();
					while(it.hasNext()){
						SelectionKey key=(SelectionKey)it.next();
						it.remove();
						if((key.readyOps()&SelectionKey.OP_ACCEPT)==SelectionKey.OP_ACCEPT){
							
							ServerSocketChannel serverSocketChannel=(ServerSocketChannel)key.channel();
							SocketChannel socketChannel=serverSocketChannel.accept();
							socketChannel.configureBlocking(false);
							socketChannel.register(selector, SelectionKey.OP_READ);
							System.out.println("Connected.   "+socketChannel.getLocalAddress());
						}
						else if((key.readyOps()&SelectionKey.OP_READ)==SelectionKey.OP_READ){
							
							//System.out.println("Received.");
							SocketChannel client=(SocketChannel)key.channel();
							ByteBuffer buff=ByteBuffer.allocate(BSIZE);
							client.read(buff);
							buff.flip();
							String encoding=System.getProperty("file.encoding");
							System.out.println("receive:   "+Charset.forName(encoding).decode(buff));
							//key.cancel();
						}
					}
				}
			} catch (Exception e) {
				// TODO: handle exception
			}
		}
	}
	
}

 

package com.wjy.nioClient;

import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;

public class NIOClient implements Runnable{
	private String sendMsg;
	private Socket client;
	private DataOutputStream out;
	public NIOClient(int port,String sendMsg){
		this.sendMsg=sendMsg;
		try {
			client=new Socket("10.13.30.160",port);
			client.setSoTimeout(10000);
			out = new DataOutputStream( (client.getOutputStream()));
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	@Override
	public void run() {
		// TODO Auto-generated method stub
		
		try {
			byte[] request = sendMsg.getBytes();
			for(int i=0;i<10;i++){
				System.out.println("Time: "+i);
				out.write(request);
				out.flush();
				Thread.sleep(5000);
			}
			client.shutdownOutput();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

}