并实现了单线程对应多个socket的功能，但是java的tutorial上依旧只有同步
的服务器例子，而且是为每一个客户建立一个线程，后来我发现了java.nio这个
包，专门是用来写异步I/O程序的，以下是一个简单的我写的例子程序：
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服务器端
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package neo.server;
import java.io.FileInputStream;import java.io.IOException;import java.net.InetSocketAddress;import java.nio.ByteBuffer;import java.nio.CharBuffer;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.nio.charset.Charset;import java.nio.charset.CharsetDecoder;import java.util.Iterator;
/** * 测试文件下载的NIOServer * * @author tenyears.cn */
public class NIOServer {
static int BLOCK = 4096;
// 处理与客户端的交互
public class HandleClient {
protected FileChannel channel;
protected ByteBuffer buffer;
public HandleClient() throws IOException
{
this.channel = new FileInputStream(filename).getChannel();
this.buffer = ByteBuffer.allocate(BLOCK);
}
public ByteBuffer readBlock()
{
try {
buffer.clear();
int count = channel.read(buffer);
buffer.flip(); if (count <= 0)
return null;
} catch (IOException e) {
e.printStackTrace(); }
return buffer;
}
public void close() {
try { channel.close();
} catch (IOException e) {
e.printStackTrace(); }
}
}
protected Selector selector;
protected String filename = "d:\\bigfile.dat"; // a big file
protected ByteBuffer clientBuffer = ByteBuffer.allocate(BLOCK);
protected CharsetDecoder decoder;
public NIOServer(int port) throws IOException {
selector = this.getSelector(port);
Charset charset = Charset.forName("GB2312");
decoder = charset.newDecoder();
}
Selector protected Selector getSelector(int port) throws IOException {
ServerSocketChannel server = ServerSocketChannel.open();
Selector sel = Selector.open();
server.socket().bind(new InetSocketAddress(port));
server.configureBlocking(false);
server.register(sel, SelectionKey.OP_ACCEPT);
return sel; }
// 监听端口
public void listen() {
try {
for (;;) {
selector.select();
Iterator iter = selector.selectedKeys().iterator();
while (iter.hasNext()) {
SelectionKey key = (SelectionKey) iter.next();
iter.remove();
handleKey(key);
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
/** * 处理key所代表的事件 * @param key * @throws IOException */ protected void handleKey(SelectionKey key) throws IOException
{
if (key.isAcceptable())
{ // 接收请求
System.out.println("receive connection....");
ServerSocketChannel server = (ServerSocketChannel) key.channel();
SocketChannel channel = server.accept();
channel.configureBlocking(false);
channel.register(selector, SelectionKey.OP_READ);
} else if (key.isReadable())
{ // 读信息
System.out.println("begin reading....");
SocketChannel channel = (SocketChannel) key.channel();
int count = channel.read(clientBuffer);
if (count > 0) {
clientBuffer.flip();
CharBuffer charBuffer = decoder.decode(clientBuffer);
System.out.println("Client >>" + charBuffer.toString());
SelectionKey wKey = channel.register(selector, SelectionKey.OP_WRITE);
wKey.attach(new HandleClient()); }
else
channel.close();
clientBuffer.clear(); }
else if (key.isWritable()) { // 写事件
System.out.println("begin writing");
SocketChannel channel = (SocketChannel) key.channel();
HandleClient handle = (HandleClient) key.attachment();
ByteBuffer block = handle.readBlock();
if (block != null)
channel.write(block);
else {
handle.close();
channel.close();
}
}
}
public static void main(String[] args) {
int port = 12345;
try {
NIOServer server = new NIOServer(port);
System.out.println("Listernint on " + port);
while (true) { server.listen(); } } catch (IOException e) { e.printStackTrace(); } }}
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