socketchanneldemo.java

精通Java核心技术的随书源代码

// ==================== Program Discription =====================
// 程序名称：示例12-14 : SocketChannelDemo.java
// 程序目的：学习java nio#SocketChannel
// ==============================================================


import java.nio.ByteBuffer;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.channels.Selector;
import java.nio.channels.SelectionKey;
import java.nio.channels.SelectableChannel;

import java.net.Socket;
import java.net.ServerSocket;
import java.net.InetSocketAddress;
import java.util.Iterator;

public class SocketChannelDemo
{
	public static int PORT_NUMBER = 23;//监听端口
	ServerSocketChannel serverChannel;
	ServerSocket serverSocket ;
	Selector selector ;
	//Allocates a new direct byte buffer.
	private ByteBuffer buffer = ByteBuffer.allocateDirect (1024);

	public static void main (String [] args)
		throws Exception
	{
		SocketChannelDemo server=new SocketChannelDemo();
		server.init(args);
		server.startWork();
	}


	public void init (String [] argv)throws Exception
	{
		int port = PORT_NUMBER;

		if (argv.length > 0) {	
			port = Integer.parseInt (argv [0]);
		}

		System.out.println ("Listening on port " + port);

		// 分配一个ServerSocketChannel
		serverChannel = ServerSocketChannel.open();
		// 从ServerSocketChannel里获得一个对应的Socket
		serverSocket = serverChannel.socket();
		// 生成一个Selector
		selector = Selector.open();

		// 把Socket绑定到端口上
		serverSocket.bind (new InetSocketAddress (port));
		//serverChannel为非bolck
		serverChannel.configureBlocking (false);

		// 通过Selector注册ServerSocetChannel
		serverChannel.register (selector, SelectionKey.OP_ACCEPT);	
		
	}

    public void startWork()throws Exception
    {
    	while (true) {
			
			int n = selector.select();//获得io准备就绪的channel数量

			if (n == 0) {
				continue;	// 没有channel准备就绪，继续执行
			}

			// 用一个iterator返回selector的selectedkeys
			Iterator it = selector.selectedKeys().iterator();

			// 处理每一个SelectionKey
			while (it.hasNext()) {
				SelectionKey key = (SelectionKey) it.next();

				// 判断是否有新的连接到达
				if (key.isAcceptable()) {
					ServerSocketChannel server =
						(ServerSocketChannel) key.channel();//返回SelectionKey的ServerSocketChannel。
					SocketChannel channel = server.accept();

					registerChannel (selector, channel,
						SelectionKey.OP_READ);

					doWork (channel);
				}

				// 判断是否有数据在此channel里需要读取
				if (key.isReadable()) {
				   
					processData (key);

				}

				// remove selectedkeys
				it.remove();
			}
		}
	}
	protected void registerChannel (Selector selector,
		SelectableChannel channel, int ops)
		throws Exception
	{
		if (channel == null) {
			return;		// could happen
		}

		// set the new channel non-blocking
		channel.configureBlocking (false);

		// register it with the selector
		channel.register (selector, ops);
	}

    //处理接收的数据
	protected void processData (SelectionKey key)
		throws Exception
	{
		
	
		SocketChannel socketChannel = (SocketChannel) key.channel();
		int count;

		buffer.clear();			// 清空buffer

		// 读取所有的数据
		while ((count = socketChannel.read (buffer)) > 0) {
			buffer.flip();		// make buffer readable

			// send the data, don't assume it goes all at once
			while (buffer.hasRemaining())
			{
				//如果收到回车键，则在返回的字符前增加[echo]$字样
				if(buffer.get()==(char)13)
				{
					buffer.clear();
					buffer.put("[echo]$".getBytes());
					buffer.flip();
					
				}
				socketChannel.write (buffer);//在socket里些数据
			}
		
			buffer.clear();		// 清空buffer
		}

		if (count < 0) {
			// count<0，说明已经读取完毕
			socketChannel.close();
		}
	}


	private void doWork (SocketChannel channel)throws Exception
	{
		buffer.clear();
		buffer.put ("Hello,I am working,please input some thing,and i will echo to you!\r\n[echo]$".getBytes());
		buffer.flip();
		//Writes a sequence of bytes to this channel from the given buffer.
		channel.write (buffer);
	}

}