java nio socket ---- 简单模式

import java.io.IOException;
import java.net.InetSocketAddress;
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.Date;
import java.util.Iterator;
import java.util.Set;

/**
 * Created by mapan on 2014/8/18.
 */
public class NioServer {

    Selector selector = null;

    public NioServer(int port) throws IOException {
        selector = Selector.open();
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.socket().bind(new InetSocketAddress(port));
        serverSocketChannel.configureBlocking(false);
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
    }

    public void handle() throws IOException {

        while (!Thread.interrupted()) {
            selector.select();
            Set<SelectionKey> selectionKeys = selector.selectedKeys();
            Iterator<SelectionKey> iterator = selectionKeys.iterator();
            while (iterator.hasNext()) {
                SelectionKey next = iterator.next();
                iterator.remove();
                if (next.isAcceptable()) {
                    ServerSocketChannel channel = (ServerSocketChannel) next.channel();
                    SocketChannel accept = channel.accept();
                    accept.configureBlocking(false);
                    accept.register(selector, SelectionKey.OP_READ);
                }else if (next.isReadable()) {
                    SocketChannel channel = (SocketChannel) next.channel();
                    ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
                    int read = channel.read(byteBuffer);

                    String readString = new String(byteBuffer.array(), 0, read).trim();
                    System.out.println(readString);
                    if (readString.equals("quit")) {
                        channel.close();
                    } else {
                       // 这里也可以不用 下面一句话注册写事件，直接通过 channel.write() 去给客户端返回数据
                        channel.register(selector, SelectionKey.OP_WRITE);
                    }
                }else  if (next.isWritable()) {
                    String date = (new Date()).toString() + "\r\n";
                    SocketChannel channel = (SocketChannel) next.channel();
                    channel.write(ByteBuffer.wrap(date.getBytes()));
                    next.interestOps(SelectionKey.OP_READ);
                }
            }
        }
    }
    public static void main(String[] args) throws IOException {

        NioServer nioServer = new NioServer(9999);
        nioServer.handle();
    }
}

说明：

    再nio socket中，打开的是双向通道，如果 建立连接以后，是直接可以写的：写的代码如下：

channel.write()

  但是这个在nio socket里面是不推荐的，建议还是通过注册相应的写事件，向客户端返回数据。

这个只是简单的一个 nio socket的事例代码。