JDK7 AIO 入门（2）-AsynchronousServerSocketChannel

JDK7 AIO 入门（二）------AsynchronousServerSocketChannel
接上篇，接下来练习通过AIO实现一个简单的TCP server。熟悉NIO的朋友应该都了解ServerSocket，在AIO中与之对应的就是AsynchronousServerSocketChannel，查看其API文档，介绍如下”An asynchronous channel for stream-oriented listening sockets. “，就是一个异步的数据流监听Socket。其主要函数有如下几个：

accept()：接受一个连接，返回一个Future，可通过Future获取到Socket的状态，和数据。
accept(A attachment, CompletionHandler<AsynchronousSocketChannel,? super A> handler)：接受连接，并为连接绑定一个CompletionHandler处理Socket连接

bind(SocketAddress local)：把ServerSocket绑定到本地端口上，等待连接。
bind(SocketAddress local, int backlog)：功能和上面一个方法一样，添加了backlog参数指定队列中挂起的连接的最大个数

open()：开启一个异步Socket通道，
open(AsynchronousChannelGroup group)：开启一个异步Socket通道，并把通道加入指定的组做资源管理

provider()：返回这个Channel的创建者

setOption(SocketOption<T> name, T value)：配置Socket参数的方法。

下面就是通过AsynchronousServerSocketChannel实现的一个简单的EchoServer，服务器会打印出收到的客户端输入，并把输入写回客户端。（注：代码只有在JDK1.7下才能编译通过）

public class AIOEchoServer {
    private AsynchronousServerSocketChannel server;

    public static void main(String[] args) throws IOException {
        AIOEchoServer aioServer = new AIOEchoServer();
        aioServer.init("localhost", 6025);
    }

    private void init(String host, int port) throws IOException {
        //ChannelGroup用来管理共享资源
        AsynchronousChannelGroup group = AsynchronousChannelGroup.withCachedThreadPool(Executors.newCachedThreadPool(), 10);
        server = AsynchronousServerSocketChannel.open(group);
        //通过setOption配置Socket
        server.setOption(StandardSocketOptions.SO_REUSEADDR, true);
        server.setOption(StandardSocketOptions.SO_RCVBUF, 16 * 1024);
        //绑定到指定的主机，端口
        server.bind(new InetSocketAddress(host, port));
        System.out.println("Listening on " + host + ":" + port);
        //输出provider
        System.out.println("Channel Provider : " + server.provider());
        //等待连接，并注册CompletionHandler处理内核完成后的操作。
        server.accept(null, new CompletionHandler<AsynchronousSocketChannel, Object>() {
            final ByteBuffer buffer = ByteBuffer.allocate(1024);

            @Override
            public void completed(AsynchronousSocketChannel result, Object attachment) {
                System.out.println("waiting....");
                buffer.clear();
                try {
                    //把socket中的数据读取到buffer中
                    result.read(buffer).get();
                    buffer.flip();
                    System.out.println("Echo " + new String(buffer.array()).trim() + " to " + result);
                   
                    //把收到的直接返回给客户端
                    result.write(buffer);
                    buffer.flip();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (ExecutionException e) {
                    e.printStackTrace();
                } finally {
                    try {
                        //关闭处理完的socket，并重新调用accept等待新的连接
                        result.close();
                        server.accept(null, this);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }

            @Override
            public void failed(Throwable exc, Object attachment) {
                System.out.print("Server failed...." + exc.getCause());
            }
        });

        //因为AIO不会阻塞调用进程，因此必须在主进程阻塞，才能保持进程存活。
        try {
            Thread.sleep(Integer.MAX_VALUE);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

运行时会打印出如下信息：
Listening on localhost:6025
Channel Provider : sun.nio.ch.BsdAsynchronousChannelProvider@625cb0bb

在客户端，可以通过telnet localhost 6025验证服务
Trying ::1...
telnet: connect to address ::1: Connection refused
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.

输入 hello，回车，客户端会打印
hello
hello
Connection closed by foreign host.

服务器端会有打印
waiting....
Echo hello to sun.nio.ch.UnixAsynchronousSocketChannelImpl[connected local=/127.0.0.1:6025 remote=/127.0.0.1:54611]

JDK7 AIO 入门（2）-AsynchronousServerSocketChannel

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