SocketChannel / ServerSocketChannel / Selector
Channel
Channel用来操作数据块，写入buffer或者从IO中读到buffer。
SocketChannel
创建
// 创建，并阻塞等待连接
SocketChannel sc = SocketChannel.open(new InetSocketAddress("abc.com",80));
// 创建，使用connect()连接
SocketChannel sc = SocketChannel.open();
sc.connect(new InetSocketAddress("abc.com",80)); // blocking
// 创建，非阻塞
SocketChannel sc = SocketChannel.open();
sc.configureBlocking(false); // set no-block
sc.connect(new InetSocketAddress("abc.com",80)); // no-blocking
// 非阻塞模式的一般处理方式——轮询！
while(true)
{
if(sc.
finishConnect() /* 立即返回，已经连接返回true，否则false */){
break;
/* connected,start write */
}
}
.isConnected()
.isConnectionPending() // 正在setup，还未open
读
int sc.read(ByteBuffer dst)
尽可能多的读数据到dst中。
返回读取的字节数量，如果读取完毕，返回-1。
while(buffer.hasRemaining() && channel.read(buffer)!=-1 )
{
}
Scatter 读取并复制到多个Buffer
ByteBuffer[] buffers = new ByteBuffer[2];
buffers[0] = ByteBuffer.allocate(1000);
buffers[1] = ByteBuffer.allocate(1000);
while(buffer[1].hasRemaining() && channel.read(buffer)!=-1 )
{
}
写
while(buffer.hasRemaining() && channel.write(buffer)!=-1 )
{
}
gather 从多个buffer读取，写入到同一个socket中
channel.write(ByteBuffer[] dsts);
关闭
if( channel.isOpen() )
{
channel.close();
}
ServerSocketChannel
创建
ServerSocketChannel ssc = ServerSocketChannel.open(); // open并非打开，而是创建
ServerSocket ss = ssc.socket();
ss.bind(new InetSocketAddress(80));
监听
.appcept();
默认是
blocking 模式。
non-blocking模式下，.accept()在没有连接的情况下立刻返回null。需要使用 Selector 处理。
Selector
Selector selector = Selector.open();
向selector注册channel
ServerSocketChannel ssc = ... ;
ssc.register(selector,SelectionKey.OP_ACCEPT/* 监听事件 */|SelectionKey.OP_CONNECT);
ssc.register(selector,OP,object state);
事件类型
SelectionKey.OP_ACCEPT
SocketChannel无本事件，ServerSocketChannel有
SelectionKey.OP_CONNECT
SelectionKey.OP_READ
SelectionKey.OP_WRITE
各个channel注册到selector后，随时可以
轮询哪些channel有了事件需要处理
selector.selectNow() // no-blocking ，没有则返回0
selector.select() //
blocing，直到至少有一个事件
selector.select(long timeout)
有事件准备好处理之后，获取对应的channel
Set selector.
selectedKeys();
关闭
selector.close()
SelectionKey
当要处理selectedKey的时候，先判断是哪个事件
SelectionKey key = selector.selectedKeys().get(0);
if(key.isAcceptable()){}
if(key.isConnectionable()){}
// 获取对应的channel
SelectableChannel c = key.channel();
// 获取附加状态
key.attachment()
// 不再跟踪
key.cancel()
DEMO:
阻塞模式下的SocketChannel与阻塞模式下的ServerSocketChannel交互（无需用到Selector）
/** * 阻塞模式下的ServerSocketChannel */ public static void startBlockingServerChannel() { new Thread(new Runnable() { @Override public void run() { ServerSocketChannel serverSocketChannel = null; try { while (true) { serverSocketChannel = ServerSocketChannel.open(); serverSocketChannel.configureBlocking(true); serverSocketChannel.bind(new InetSocketAddress(90)); System.out.println("[server]accepting..."); SocketChannel client = serverSocketChannel.accept(); ByteBuffer dst = ByteBuffer.allocate(1024); client.read(dst); String result = new String(dst.array(), "UTF-8"); System.out.println("->" + result); serverSocketChannel.close(); } } catch (IOException e) { e.printStackTrace(); } finally { serverSocketChannel.close(); } } }).start(); } /** * 阻塞SocketChanel调用ServerSocketChannel */ public static void startBlockingClinetUsingSocketChannel() { new Thread(new Runnable() { @Override public void run() { SocketChannel s = null; try { System.out.println("[client]start a client socket:"); s = SocketChannel.open(); //s.configureBlocking(true); System.out.println("[client]try connect..."); s.connect(new InetSocketAddress("127.0.0.1", 90)); System.out.println("[client]after connect"); ByteBuffer src = ByteBuffer.allocate(20); src.put("Hello".getBytes("UTF-8")); src.flip(); // 为读准备好 s.write(src); s.close(); } catch (Exception e) { e.printStackTrace(); } finally { try { s.close(); } catch (IOException e) { e.printStackTrace(); } } } }).start(); }
DEMO:
非阻塞模式下的SocketChannel作为客户端
public static void startNoBlocingSocketChannelAsClinet() { SocketChannel socketChannel = null; try { System.out.println("[client]start a client socket:"); s = SocketChannel.open(); s.configureBlocking(false); s.connect(new InetSocketAddress("127.0.0.1", 90)); while (true) { if (s.finishConnect()) { System.out.println("[client]connected..."); ByteBuffer src = ByteBuffer.allocate(100); src.put("Hello".getBytes("UTF-8")); src.flip(); s.write(src); break; } } } catch (Exception e) { } finally { /*close*/ } }
DEMO:
非阻塞模式下的ServerSocketChannel + Selector 实现服务器端（单线程多通道）
public static void startNoBlockingServerChannel() { new Thread(new Runnable() { @Override public void run() { ServerSocketChannel serverSocketChannel = null; Selector selector = null; try { selector = Selector.open(); serverSocketChannel = ServerSocketChannel.open(); serverSocketChannel.configureBlocking(false); serverSocketChannel.socket() .bind(new InetSocketAddress(90)); // register to selector serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT); // 轮询selector while (true) { System.out.println( "[server] Selector select and blocking ..."); selector.select(); // blocking,wait until 1 event Set<SelectionKey> keys = selector.selectedKeys(); // not .keys() Iterator iter = keys.iterator(); while (iter.hasNext()) { SelectionKey key = (SelectionKey) iter.next(); iter.remove(); // 以下判断最好使用 if else if (key.isValid() == false) { continue; } else if (key.isAcceptable()) { SocketChannel client = ((ServerSocketChannel) key.channel()).accept(); client.configureBlocking(false); // 继续设置为非阻塞模式（也可以是阻塞，直接处理） client.register(selector, SelectionKey.OP_READ); // 继续向Selector注册 } else if (key.isReadable()) { // start read SocketChannel client = (SocketChannel) key.channel(); ByteBuffer bf = ByteBuffer.allocate(1000); int count = client.read(bf); System.out.println("-->" + new String(bf.array(), "UTF-8")); // bf.flip(); key.cancel(); } else if (key.isWritable()) { // 不做处理 } } } } catch (IOException e) { e.printStackTrace(); } finally { /* close selector and ServerSocketChannel*/ } } }).start(); }