Java NIO

ByteBuffer buffer = ByteBuffer.wrap (GREETING.getBytes( )); 
ServerSocketChannel ssc = ServerSocketChannel.open( ); 
ssc.socket( ).bind (new InetSocketAddress (port)); 
ssc.configureBlocking (false); //non-blocking

while (true) { 
    System.out.println ("Waiting for connections"); 
    SocketChannel sc = ssc.accept( ); //不会blocking直接返回
    if (sc == null) { 
        // no connections, snooze a while 
        Thread.sleep (2000); } 
    else { 
        System.out.println ("Incoming connection from: " + sc.socket().getRemoteSocketAddress( ));  
        buffer.rewind( ); 
        sc.write (buffer); 
        sc.close( ); } } 

InetSocketAddress addr = new InetSocketAddress (host, port); 
SocketChannel sc = SocketChannel.open( ); 
sc.configureBlocking (false); //设置non-blocking
sc.connect (addr); //不会阻塞等待
while ( ! sc.finishConnect( )) { 
    doSomethingElse( ); } 
doSomethingWithChannel (sc); sc.close( ); 

Selector selector = Selector.open( ); 
channel1.register (selector, SelectionKey.OP_READ); 
channel2.register (selector, SelectionKey.OP_WRITE); 
channel3.register (selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE); 
// Wait up to 10 seconds for a channel to become ready 
readyCount = selector.select (10000); 

package java.nio.channels;
//ops, selector所关心的通道操作,读(read)，写(write)，连接(connect)和接受(accept)
public abstract SelectionKey register (Selector sel, int ops) throws ClosedChannelException; 

public abstract class SelectionKey { 
    public static final int OP_READ; 
    public static final int OP_WRITE; 
    public static final int OP_CONNECT; 
    public static final int OP_ACCEPT; 
    public abstract SelectableChannel channel( ); 
    public abstract Selector selector( ); 
    public abstract void cancel( ); 
    public abstract boolean isValid( ); 
    public abstract int interestOps( ); 
    public abstract void interestOps (int ops); 
    public abstract int readyOps( ); 
    public final boolean isReadable( ); 
    public final boolean isWritable( );
    public final boolean isConnectable( );
    public final boolean isAcceptable( ); 
    public final Object attach (Object ob) 
    public final Object attachment( ) } 

// Allocate an unbound server socket channel 
ServerSocketChannel serverChannel = ServerSocketChannel.open(); 
// Get the associated ServerSocket to bind it with ServerSocket 
serverSocket = serverChannel.socket(); 
// Create a new Selector for use below Selector 
selector = Selector.open(); 
// Set the port the server channel will listen to 
serverSocket.bind(new InetSocketAddress(port)); 
// Set nonblocking mode for the listening socket 
serverChannel.configureBlocking(false);
// Register the ServerSocketChannel with the Selector 
serverChannel.register(selector, SelectionKey.OP_ACCEPT); //关注accept

while (true) { 
// This may block for a long time. Upon returning, the 
// selected set contains keys of the ready channels. 
int n = selector.select(); 
if (n == 0) { 
    continue; // nothing to do
}

// Get an iterator over the set of selected keys 
Iterator it = selector.selectedKeys().iterator(); 
// Look at each key in the selected set 
while (it.hasNext()) { 
    SelectionKey key = (SelectionKey) it.next(); 
    // Is a new connection coming in? 
    if (key.isAcceptable()) { 
        ServerSocketChannel server = (ServerSocketChannel) key.channel(); 
        SocketChannel channel = server.accept(); 
        registerChannel(selector, channel, SelectionKey.OP_READ); //Accept后设置成关注Read
        sayHello(channel); } 
    // Is there data to read on this channel? 
    if (key.isReadable()) { 
        readDataFromSocket(key); } 
} } } 

本文章摘自博客园，原文发布日期：2013-10-10