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：
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) {}
}
}
}