为了加强对socket及java IO流编程的回顾，本文作了一个文件传输的实例。针对java不同对IO流的不同实现，本文也分别基于BIO、NIO、AIO实现三种传输，同时本文采用了缓冲输入/输出流来包装输出流，再采用数据输入/输出输出流包装缓冲流，加快传输的速度。最后本文基于大文件对三种方式基本传输效率对比。对于每一种传输方式分别实现服务端和客户端，并通过服务端发送文件到客户端，（同理可以实现客户端到服务器端的文件发送）
服务端：BIOServer.java
package zmx.socket.filethransfer.bio; import java.io.BufferedInputStream; import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.net.ServerSocket; import java.net.Socket; /** * 本例实现基于BIO的Socket文件传输，客户端连接服务器后，服务器发送一个文件到客户端， * 客户端接受文件，保存到本地。(同理可实现客户端向服务器的文件发送) * * 本类是服务端：实现接受连接和发送文件 * @author zhangwenchao */ public class BIOServer { public static final int port=8821; public static final int bufferSize = 8192; public void serverStart(){ Socket s =null; //连接 try { ServerSocket ss = new ServerSocket(port);//初始化ServerSocket File f = new File("E:\\1.jpg"); System.out.println("要发送的文件为："+f.getName()+" 文件大小："+f.length()); while(true){//不断循环接受客户端请求 System.out.println("服务器正在监听端口："+port+"..."); // public Socket accept() throws IOException // 侦听并接受到此套接字的连接。此方法在进行连接之前一直阻塞。 s = ss.accept(); //建立连接 System.out.println("Socket连接已经建立成功！"); //Socket输入流： 读取客户端发送过来的数据 DataInputStream dis = new DataInputStream(new BufferedInputStream(s.getInputStream())); byte message = dis.readByte(); System.out.println(message); //文件输入流：读取文件 DataInputStream fis = new DataInputStream(new BufferedInputStream(new FileInputStream(f))); //Socket输出流： 发送文件 DataOutputStream dos = new DataOutputStream(s.getOutputStream()); //将文件名及长度传给客户端。这里要真正适用所有平台，例如中文名的处理，还需要加工，具体可以参见Think In Java 4th里有现成的代码。 dos.writeUTF(f.getName()); dos.flush(); dos.writeLong((long) f.length()); dos.flush(); byte[] buf = new byte[bufferSize]; int len = 0; while((len=fis.read(buf))!=-1){ dos.write(buf, 0, len); } dos.flush(); // 注意关闭socket链接哦，不然客户端会等待server的数据过来， // 直到socket超时，导致数据不完整。 fis.close(); s.close(); System.out.println("文件传输完成"); } } catch (IOException e) { e.printStackTrace(); System.out.println("网络连接出现异常！"); } } public static void main(String arg[]) { new BIOServer().serverStart(); } }客户端：BIOSocketUti.java+BIOClient.java
BIOSocketUtil.java
package zmx.socket.filethransfer.bio; import java.io.BufferedInputStream; import java.io.DataInputStream; import java.io.DataOutputStream; import java.net.Socket; /** * Socket连接工具 * @author zhangwenchao * */ public class BIOSocketUtil{ /** * 创建socket连接 * @throws Exception * exception */ public static Socket CreateConnection(String ip, int port) throws Exception { try { Socket socket = new Socket(ip, port); return socket; } catch (Exception e) { e.printStackTrace(); throw e; } finally { } } /** * 发送一条信息，通知服务器本机的操作系统类型 * @param sendMessage 0x1:windows 0x2:unix 0x3:Linux * @throws Exception */ public static void sendMessage(Socket socket,String sendMessage) throws Exception { DataOutputStream outputStream = null; try { outputStream = new DataOutputStream(socket.getOutputStream()); if (sendMessage.equals("Windows")) { outputStream.writeByte(0x1); outputStream.flush(); return; } if (sendMessage.equals("Unix")) { outputStream.writeByte(0x2); outputStream.flush(); return; } if (sendMessage.equals("Linux")) { outputStream.writeByte(0x3); outputStream.flush(); } else { outputStream.writeUTF(sendMessage); outputStream.flush(); } } catch (Exception e) { System.out.println("发送消息错误" + "\n"); e.printStackTrace(); if (outputStream != null) outputStream.close(); throw e; } finally { } } /** * 获取输入流 * @return * @throws Exception */ public static DataInputStream getMessageStream(Socket socket) throws Exception { try { DataInputStream inputStream = new DataInputStream(new BufferedInputStream(socket.getInputStream())); return inputStream; } catch (Exception e) { e.printStackTrace(); throw e; } finally { } } /** * 关闭连接 */ public static void shutDownConnection(Socket socket) { try { if (socket != null){ socket.close(); } } catch (Exception e) { } } }BIOClient.java
package zmx.socket.filethransfer.bio; import java.io.BufferedOutputStream; import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.FileOutputStream; import java.net.Socket; /** * 客户端：发送一条消息 通知服务器本地操作系统类型，然后接受服务器发送的文件 * @author zhangwenchao * */ public class BIOClient { public static final int bufferSize = 8192; private static void getFileMessage(Socket socket) { if (socket == null) return; DataInputStream inputStream = null; try { inputStream = BIOSocketUtil.getMessageStream(socket); //根据socket获取输入流 } catch (Exception e) { System.out.print("接收消息缓存错误\n"); return; } try { //本地保存路径，文件名会自动从服务器端继承而来。 String savePath = "E:\\local\\"; byte[] buf = new byte[bufferSize]; int passedlen = 0; //统计收到的数据 //1、读取文件名 savePath += inputStream.readUTF(); //根据文件名新建一个文件输出流 DataOutputStream fileOut = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(savePath))); //2、读取文件长度 long fileLength = inputStream.readLong(); System.out.println("文件的长度为:" + fileLength + "\n"); System.out.println("开始接收文件..." + "\n"); //3、读取文件内容 int len = 0; while((len=inputStream.read(buf))!=-1){ passedlen += len; //下面进度条本为图形界面的prograssBar做的，这里如果是打文件，可能会重复打印出一些相同的百分比 System.out.println("文件接收了" + (passedlen * 100/ fileLength) + "%\n"); fileOut.write(buf, 0, len); } System.out.println("接收完成，文件存为" + savePath + "\n"); fileOut.close(); } catch (Exception e) { System.out.println("接收消息错误" + "\n"); return; } } public static void main(String arg[]) { String ip = "localhost";// 设置成服务器IP int port = 8821; String sendMessage = "Windwos"; try { Socket socket = BIOSocketUtil.CreateConnection(ip, port); System.out.print("连接服务器成功!" + "\n"); BIOSocketUtil.sendMessage(socket, sendMessage); //发送数据 getFileMessage(socket); //获取数据 } catch (Exception e) { System.out.print("连接服务器失败!" + "\n"); } } }运行测试结果：
要发送的文件为：1.jpg 文件大小：917070 服务器正在监听端口：8821... Socket连接已经建立成功！ 0 文件传输完成！
1、NIOServer.java
package zmx.socket.filethransfer.nio; import java.io.FileOutputStream; import java.net.InetSocketAddress; import java.net.ServerSocket; import java.nio.ByteBuffer; 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.Set; public class NIOServer{ private int port = 8000; /* 发送数据缓冲区 */ private static ByteBuffer sendBuffer = ByteBuffer.allocate(1024); /* 接受数据缓冲区 */ private static ByteBuffer revBuffer = ByteBuffer.allocate(1024); private static Selector selector; private static FileOutputStream fout; private static FileChannel ch; public NIOServer(){ try{ init(); } catch(Exception e){ e.printStackTrace(); } } private void init() throws Exception{ ServerSocketChannel serverSocketChannel = ServerSocketChannel.open(); serverSocketChannel.configureBlocking(false); ServerSocket serverSocket = serverSocketChannel.socket(); serverSocket.bind(new InetSocketAddress(port)); selector = Selector.open(); serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT); System.out.println("server start on port:" + port); while (true) { try { selector.select();// 返回值为本次触发的事件数 Set<SelectionKey> selectionKeys = selector.selectedKeys(); for (SelectionKey key : selectionKeys) { ServerSocketChannel server = null; SocketChannel client = null; int count = 0; if (key.isAcceptable()) { server = (ServerSocketChannel) key.channel(); System.out.println("有客户端连接进入=============)"); client = server.accept(); client.configureBlocking(false); client.register(selector, SelectionKey.OP_READ|SelectionKey.OP_WRITE); fout = new FileOutputStream("E:\\local\\" + client.hashCode() + ".jpg"); ch = fout.getChannel(); } else if (key.isReadable()) { client = (SocketChannel) key.channel(); revBuffer.clear(); count = client.read(revBuffer); int k = 0; // 循环读取缓存区的数据， while(count > 0){ System.out.println("k=" + (k++) + " 读取到数据量:" + count); revBuffer.flip(); ch.write(revBuffer); fout.flush(); revBuffer.clear(); count = client.read(revBuffer); } if(count == -1){ client.close(); ch.close(); fout.close(); } }else if (key.isWritable()) { System.out.println("selectionKey.isWritable()"); } } System.out.println("=======selectionKeys.clear()"); selectionKeys.clear(); } catch (Exception e) { e.printStackTrace(); break; } } } public static void main(String[] args){ new NIOServer(); } }2、NIOClient.java
package zmx.socket.filethransfer.nio; import java.io.FileInputStream; import java.net.InetSocketAddress; import java.nio.ByteBuffer; import java.nio.channels.FileChannel; import java.nio.channels.SelectionKey; import java.nio.channels.Selector; import java.nio.channels.SocketChannel; import java.util.Set; public class NIOClient { private int port = 8000; /* 发送数据缓冲区 */ private static ByteBuffer sendBuffer = ByteBuffer.allocate(1024); /* 接受数据缓冲区 */ private static ByteBuffer revBuffer = ByteBuffer.allocate(1024); private InetSocketAddress SERVER; private static Selector selector; private static SocketChannel client; public NIOClient(){ try{ SERVER = new InetSocketAddress("localhost", port); init(); } catch(Exception e){ e.printStackTrace(); } } private void init(){ try { SocketChannel socketChannel = SocketChannel.open(); socketChannel.configureBlocking(false); selector = Selector.open(); socketChannel.register(selector, SelectionKey.OP_CONNECT); socketChannel.connect(SERVER); while (true) { selector.select(); Set<SelectionKey> keySet = selector.selectedKeys(); for(SelectionKey key : keySet) { if(key.isConnectable()){ client = (SocketChannel)key.channel(); client.finishConnect(); client.register(selector, SelectionKey.OP_WRITE|SelectionKey.OP_READ); }else if(key.isWritable()){ sendFile(client); }else if(key.isReadable()){ System.out.println("selectionKey.isReadable()"); } } keySet.clear(); } } catch (Exception e) { e.printStackTrace(); } } private void sendFile(SocketChannel client) { FileInputStream fis = null; FileChannel channel = null; try { System.out.println("文件发送开始...."); fis = new FileInputStream("E:\\1.jpg"); channel = fis.getChannel(); int i = 1; int count = 0; while((count = channel.read(sendBuffer)) != -1) { sendBuffer.flip(); int send = client.write(sendBuffer); System.out.println("i===========" + (i++) + " count:" + count + " send:" + send); // 服务器端可能因为缓存区满，而导致数据传输失败，需要重新发送 while(send == 0){ Thread.sleep(10); send = client.write(sendBuffer); System.out.println("i重新传输====" + i + " count:" + count + " send:" + send); } sendBuffer.clear(); } System.out.println("文件发送完成！"); } catch (Exception e) { e.printStackTrace(); } finally { try { channel.close(); fis.close(); client.close(); } catch (Exception e) { e.printStackTrace(); } } } public static void main(String[] args){ new NIOClient(); } }
运行测试结果：
文件发送开始.... i===========1 count:1024 send:1024 i===========2 count:1024 send:1024 i===========3 count:1024 send:1024 i===========4 count:1024 send:1024 i===========5 count:1024 send:1024
...
文件发送完成！
