通过SocketChannel回送客户端

import java.io.BufferedReader;

import java.io.EOFException;

import java.io.IOException;/**from n o w  j a v a  . c o m**/

import java.io.InputStreamReader;

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.Date;

import java.util.Iterator;


class NioEchoClient implements Runnable {
// 来自 nowjava.com

  private static final int PORT_NUMBER = 9000;

  private static final long TIME_OUT = 3000;

  private static final byte LF = 0x0A;

  private static final byte CR = 0x0D;

  private String mHostname;

  private int mPort;

  private Selector mSelector;

  private final ByteBuffer mReadBuffer = ByteBuffer.allocate(8192);


  public NioEchoClient(String host, int portNumber) throws IOException {

    this.mHostname = host;

    this.mPort = portNumber;

    this.mSelector = Selector.open();

  }


  @Override

  public void run() {

    SocketChannel client = null;

    try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) {

      client = createSocketChannel();


      if (!client.isConnected()) {

        client.finishConnect();

      }


      System.out.println("input data to send to the server.");


      String line = null;

      while ((line = keyboard.readLine()) != null) {

        if ("quit".equals(line))

          break;


        client.register(mSelector, SelectionKey.OP_WRITE);


        while (mSelector.select(TIME_OUT) != 0) {

          Iterator<SelectionKey> selectedKeys = mSelector.selectedKeys().iterator();

          while (selectedKeys.hasNext()) {

            SelectionKey key = selectedKeys.next();

            selectedKeys.remove();

            if (!key.isValid())

              continue;


            if (key.isReadable()) {

              readData(key);

            } else if (key.isWritable()) {

              writeData(key, line);

            }


          }

        }

      }

    } catch (EOFException e) {


    } catch (IOException e) {

      e.printStackTrace();

    } finally {

      try {

        client.close();

      } catch (IOException e) {

        e.printStackTrace();

      }

    }

    System.out.println("client exits");

  }


  private void writeData(SelectionKey key, String line) throws IOException {

    SocketChannel client = (SocketChannel) key.channel();

    mReadBuffer.clear();

    mReadBuffer.put(line.getBytes());

    mReadBuffer.put(LF);


    mReadBuffer.flip();


    client.write(mReadBuffer);


    System.out.println("Client send " + line + " at " + new Date());

    client.keyFor(mSelector).interestOps(SelectionKey.OP_READ);

  }


  private void readData(SelectionKey key) throws IOException {

    SocketChannel client = (SocketChannel) key.channel();

    mReadBuffer.clear();


    int numRead;

    int totalRead = 0;

    while ((numRead = client.read(mReadBuffer)) > 0) {

      totalRead = numRead;

    }


    if (numRead < 0) {

      client.close();

      key.cancel();

      throw new EOFException();

    }


    mReadBuffer.flip();

    byte[] receivedData = new byte[totalRead];

    System.arraycopy(mReadBuffer.array(), 0, receivedData, 0, totalRead);