本文实例讲述了Java使用Socket通信传输文件的方法。分享给大家供大家参考，具体如下：

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前面几篇文章介绍了使用Java的Socket编程和NIO包在Socket中的应用，这篇文章说说怎样利用Socket编程来实现简单的文件传输。

这里由于前面一片文章介绍了NIO在Socket中的应用，所以这里在读写文件的时候也继续使用NIO包，所以代码看起来会比直接使用流的方式稍微复杂一点点。

下面的示例演示了客户端向服务器端发送一个文件，服务器作为响应给客户端回发一个文件。这里准备两个文件E:/test/server_send.log和E:/test/client.send.log文件，在测试完毕后在客户端和服务器相同目录下会多出两个文件E:/test/server_receive.log和E:/test/client.receive.log文件。

下面首先来看看Server类，主要关注其中的sendFile和receiveFile方法。

package com.googlecode.garbagecan.test.socket.nio;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.FileChannel;
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.logging.Level;
import java.util.logging.Logger;
public class MyServer4 {
  private final static Logger logger = Logger.getLogger(MyServer4.class.getName());
  public static void main(String[] args) {
    Selector selector = null;
    ServerSocketChannel serverSocketChannel = null;
    try {
      // Selector for incoming time requests
      selector = Selector.open();
      // Create a new server socket and set to non blocking mode
      serverSocketChannel = ServerSocketChannel.open();
      serverSocketChannel.configureBlocking(false);
      // Bind the server socket to the local host and port
      serverSocketChannel.socket().setReuseAddress(true);
      serverSocketChannel.socket().bind(new InetSocketAddress(10000));
      // Register accepts on the server socket with the selector. This
      // step tells the selector that the socket wants to be put on the
      // ready list when accept operations occur, so allowing multiplexed
      // non-blocking I/O to take place.
      serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
      // Here's where everything happens. The select method will
      // return when any operations registered above have occurred, the
      // thread has been interrupted, etc.
      while (selector.select() > 0) {
        // Someone is ready for I/O, get the ready keys
        Iterator it = selector.selectedKeys().iterator();
        // Walk through the ready keys collection and process date requests.
        while (it.hasNext()) {
          SelectionKey readyKey = it.next();
          it.remove();
          // The key indexes into the selector so you
          // can retrieve the socket that's ready for I/O
          doit((ServerSocketChannel) readyKey.channel());
        }
      }
    } catch (ClosedChannelException ex) {
      logger.log(Level.SEVERE, null, ex);
    } catch (IOException ex) {
      logger.log(Level.SEVERE, null, ex);
    } finally {
      try {
        selector.close();
      } catch(Exception ex) {}
      try {
        serverSocketChannel.close();
      } catch(Exception ex) {}
    }
  }
  private static void doit(final ServerSocketChannel serverSocketChannel) throws IOException {
    SocketChannel socketChannel = null;
    try {
      socketChannel = serverSocketChannel.accept();
      receiveFile(socketChannel, new File("E:/test/server_receive.log"));
      sendFile(socketChannel, new File("E:/test/server_send.log"));
    } finally {
      try {
        socketChannel.close();
      } catch(Exception ex) {}
    }
  }
  private static void receiveFile(SocketChannel socketChannel, File file) throws IOException {
    FileOutputStream fos = null;
    FileChannel channel = null;
    try {
      fos = new FileOutputStream(file);
      channel = fos.getChannel();
      ByteBuffer buffer = ByteBuffer.allocateDirect(1024);
      int size = 0;
      while ((size = socketChannel.read(buffer)) != -1) {
        buffer.flip();
        if (size > 0) {
          buffer.limit(size);
          channel.write(buffer);
          buffer.clear();
        }
      }
    } finally {
      try {
        channel.close();
      } catch(Exception ex) {}
      try {
        fos.close();
      } catch(Exception ex) {}
    }
  }
  private static void sendFile(SocketChannel socketChannel, File file) throws IOException {
    FileInputStream fis = null;
    FileChannel channel = null;
    try {
      fis = new FileInputStream(file);
      channel = fis.getChannel();
      ByteBuffer buffer = ByteBuffer.allocateDirect(1024);
      int size = 0;
      while ((size = channel.read(buffer)) != -1) {
        buffer.rewind();
        buffer.limit(size);
        socketChannel.write(buffer);
        buffer.clear();
      }
      socketChannel.socket().shutdownOutput();
    } finally {
      try {
        channel.close();
      } catch(Exception ex) {}
      try {
        fis.close();
      } catch(Exception ex) {}
    }
  }
}

名称栏目：Java使用Socket通信传输文件的方法示例-创新互联
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