【发布时间】：2016-02-01 02:25:03
【问题描述】：
我正在尝试使用 Java NIO API 将 mp3 文件从服务器传输到客户端。
特别是，我正在尝试使用 transferTo 和 transferFrom 方法。
我已经检查过服务器是否正确识别文件并传输到 FileChannel。
但是，从客户端的角度来看，它认为连接到服务器的FileChannel的大小为0，可以解释为客户端没有从该通道接收到任何文件。
这是服务器和客户端控制台上的结果。
[服务器]
Server is started...
java.nio.channels.SocketChannel[connected local=/127.0.0.1:7777 remote=/127.0.0.1:60430]Here comes a new client!
!!write activated!!
Channel size : 3622994
filename : C:\Users\InhoKim\Music\5 O'clock - Black Nut.mp3
java.nio.channels.SocketChannel[connected local=/127.0.0.1:7777 remote=/127.0.0.1:60430]The number of files transferred : 1
[客户]
!!read activated!!
Channel size : 0
我该如何解决这个问题？
这是服务器和客户端的完整代码
[服务器]
import java.io.File;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.net.ServerSocket;
import java.net.InetSocketAddress;
import java.nio.channels.SelectableChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.nio.channels.FileChannel;
import java.io.FileInputStream;
import java.util.Set;
import java.nio.ByteBuffer;
public class MusicServer {
private Selector selector = null;
private ServerSocketChannel serverSocketChannel = null;
private ServerSocket serverSocket = null;
File dir = new File("C:\\Users\\InhoKim\\Music\\");
boolean test = true;
public static void main(String[] args) {
MusicServer ms = new MusicServer();
ms.initServer();
ms.startServer();
}
public void initServer() {
try {
selector = Selector.open();
serverSocketChannel = ServerSocketChannel.open();
serverSocketChannel.configureBlocking(false);
serverSocket = serverSocketChannel.socket();
InetSocketAddress isa = new InetSocketAddress("localhost", 7777);
serverSocket.bind(isa);
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
} catch(Exception e) {e.printStackTrace();}
}
public void startServer() {
System.out.println("Server is started...");
try {
while (true) {
selector.select();
Set<SelectionKey> keys = selector.selectedKeys();
for (SelectionKey key : keys) {
SelectableChannel channel = key.channel();
if (channel instanceof ServerSocketChannel) {
if (key.isAcceptable())
accept(key);
} else {
if (key.isWritable()) {
if(test)
write(key);
}
}
}
}
} catch(Exception e) {e.printStackTrace();}
}
private void accept(SelectionKey key) {
ServerSocketChannel server = (ServerSocketChannel) key.channel();
try {
SocketChannel sc = server.accept();
if (sc == null) return;
sc.configureBlocking(false);
sc.register(selector, SelectionKey.OP_WRITE);
System.out.println(sc.toString() + "Here comes a new client!");
} catch(Exception e) {e.printStackTrace();}
}
private void write(SelectionKey key) {
if(test)
System.out.println("!!write activated!!");
test = false;
SocketChannel sc = (SocketChannel) key.channel();
try {
File[] files = dir.listFiles();
int count = 0;
for (File file : files) {
count++;
FileInputStream fis = new FileInputStream(file);
FileChannel inChannel = fis.getChannel();
System.out.println("Channel size : " + (int)inChannel.size());
System.out.println("filename : " + file);
inChannel.transferTo(0, (int)inChannel.size(), sc);
fis.close();
break;
}
System.out.println(sc.toString() + "The number of files transferred : " + count);
} catch(Exception e) {e.printStackTrace();}
}
}
[客户]
import java.io.File;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.channels.SelectionKey;
import java.net.InetSocketAddress;
import java.nio.channels.FileChannel;
import java.util.Set;
import java.io.FileOutputStream;
import java.nio.ByteBuffer;
public class MusicClient {
private Selector selector = null;
private SocketChannel sc = null;
int count = 0;
public static void main(String[] args) {
MusicClient mc = new MusicClient();
mc.startServer();
}
public void initServer() {
try {
selector = Selector.open();
sc = SocketChannel.open(new InetSocketAddress("127.0.0.1", 7777));
sc.configureBlocking(false);
sc.register(selector, SelectionKey.OP_READ);
} catch(Exception e) {e.printStackTrace();}
}
public void startServer() {
initServer();
startReader();
}
public void startReader() {
try {
while (true) {
selector.select();
Set<SelectionKey> keys = selector.selectedKeys();
for (SelectionKey key : keys) {
if (key.isReadable()) {
read(key);
System.exit(0);
}
}
}
} catch(Exception e) {e.printStackTrace();}
}
private void read(SelectionKey key) {
System.out.println("!!read activated!!");
SocketChannel sc = (SocketChannel) key.channel();
try {
File dir = new File("D:\\Target2\\");
FileOutputStream fos = new FileOutputStream(dir + "\\" + count + ".mp3"); // file name has been set as a number
count++;
FileChannel outChannel = fos.getChannel();
System.out.println("Channel size : " + (int)outChannel.size());
outChannel.transferFrom(sc, 0, (int)outChannel.size());
fos.close();
} catch(Exception e) {e.printStackTrace();}
}
}
【问题讨论】：
标签： java networking io nio file-transfer