java nio socket简单示例

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1、说明

java nio底层基于Reactor模型，采用多路复用IO模型，由一个专门的线程来处理所有的 IO 事件，并负责分发。基于事件驱动机制能够在事件到的时触发，而不是同步的去监视事件。线程之间的通讯是通过 wait、notify等方式通讯，保证每次上下文切换都是有意义的，减少无谓的线程切换。

服务端和客户端各自维护一个管理通道的对象selector，其能检测一个或多个通道 (channel) 上的事件。例如：如果服务端selector上注册了读事件，某时刻客户端给服务端发送了一些数据（阻塞I/O这时会调用read()方法阻塞地读取数据），NIO的服务端会在selector中添加一个读事件，服务端的处理线程会轮询地访问selector，如果访问selector时发现有感兴趣的事件到达，则处理这些事件，如果没有感兴趣的事件到达，则处理线程会一直阻塞直到收到感兴趣的事件到达为止。

示例代码如下所示。希望对你有所帮助。

2、服务器端代码实现

package nio;import java.io.IOException;import java.net.InetSocketAddress;import java.nio.ByteBuffer;import java.nio.channels.ClosedChannelException;import java.nio.channels.SelectionKey;import java.nio.channels.Selector;import java.nio.channels.ServerSocketChannel;import java.nio.channels.SocketChannel;import java.util.Iterator;public class NioServer {    private Selector selector;    public static void main(String[] args) throws IOException {        NioServer server = new NioServer();        server.initServer(8098);        server.listener();    }    public void initServer(int port) throws IOException {        ServerSocketChannel channel = ServerSocketChannel.open();        channel.configureBlocking(false);        channel.socket().bind(new InetSocketAddress(port));        this.selector = Selector.open();        channel.register(selector, SelectionKey.OP_ACCEPT);        System.err.println();    }    public void listener() throws IOException {        while (true) {            selector.select();            Iterator<SelectionKey> iterator = this.selector.selectedKeys().iterator();            System.err.println("server size: " + this.selector.selectedKeys().size());            while (iterator.hasNext()) {                SelectionKey key = iterator.next();                iterator.remove();                if (key.isAcceptable()) {                   accept(key);                } else if (key.isReadable()) {                    read(key);                } else if(key.isWritable()){                    write(key);                }             }        }    }    private void accept(SelectionKey key) {         try {            ServerSocketChannel server = (ServerSocketChannel) key.channel();             SocketChannel channel = server.accept();             channel.configureBlocking(false);             channel.write(ByteBuffer.wrap(new String("I am server, I send a msg").getBytes()));             channel.register(this.selector, SelectionKey.OP_READ);        } catch (ClosedChannelException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }    private void write(SelectionKey key) {        try {            SocketChannel channel = (SocketChannel) key.channel();            String str = new String("server send msg to client...");            channel.configureBlocking(false);            channel.write(ByteBuffer.wrap(str.getBytes()));            System.err.println("服务器write: " + str);            channel.register(this.selector, SelectionKey.OP_READ);        } catch (IOException e) {            e.printStackTrace();        }    }    private void read(SelectionKey key) throws IOException {        SocketChannel channel = (SocketChannel) key.channel();        channel.configureBlocking(false);        ByteBuffer buffer = ByteBuffer.allocate(100);        channel.read(buffer);        byte[] array = buffer.array();        String msg = new String(array).trim();        System.err.println("服务器read: " + msg);        channel.register(this.selector, SelectionKey.OP_WRITE);    }}

3、客户端代码实现

package nio;import java.io.IOException;import java.net.InetSocketAddress;import java.nio.ByteBuffer;import java.nio.channels.ClosedChannelException;import java.nio.channels.SelectionKey;import java.nio.channels.Selector;import java.nio.channels.SocketChannel;import java.util.Iterator;public class NioClient {    // 通道管理器    private Selector selector;    private volatile int count = 0;    public static void main(String[] args) throws IOException {        NioClient client = new NioClient();        client.init("127.0.0.1", 8098);        client.listen();    }    public void init(String ip, int port) throws IOException {        // 获得一个Socket通道        SocketChannel channel = SocketChannel.open();        // 设置通道为非阻塞        channel.configureBlocking(false);        // 获得一个通道管理器        this.selector = Selector.open();        // 客户端连接服务器,其实方法执行并没有实现连接        channel.connect(new InetSocketAddress(ip, port));        // 将通道管理器和该通道绑定，并为该通道注册SelectionKey.OP_CONNECT事件。        channel.register(selector, SelectionKey.OP_CONNECT);    }    public void listen() throws IOException {        // 轮询访问selector        while (true) {            //阻塞直到有事件            selector.select();            // 获得selector中选中的项的迭代器            Iterator ite = this.selector.selectedKeys().iterator();            while (ite.hasNext()) {                SelectionKey key = (SelectionKey) ite.next();                // 删除已选的key                ite.remove();                // 连接事件发生                if (key.isConnectable()) {                    connect(key);                } else if (key.isReadable()) {                    read(key);                }else if(key.isWritable()) {                    write(key);                }            }        }    }    private void write(SelectionKey key) {        try {            SocketChannel channel = (SocketChannel) key.channel();            channel.configureBlocking(false);            String str = new String("server send msg to client...");            channel.write(ByteBuffer.wrap(str.getBytes()));            System.err.println("客户端write: " + str +  "  " +count++);            try {                Thread.sleep(1000);            } catch (InterruptedException e) {                e.printStackTrace();            }            channel.register(this.selector, SelectionKey.OP_READ);        } catch (IOException e) {            e.printStackTrace();        }    }    private void connect(SelectionKey key) {        try {            SocketChannel channel = (SocketChannel) key.channel();            System.err.println("client size: " + this.selector.selectedKeys().size());            // 如果正在连接，则完成连接            if (channel.isConnectionPending()) {                channel.finishConnect();            }            // 设置成非阻塞            channel.configureBlocking(false);            // 在这里可以给服务端发送信息哦            channel.write(ByteBuffer.wrap(new String("I am client, I am send a request to server...").getBytes()));            // 在和服务端连接成功之后，为了可以接收到服务端的信息，需要给通道设置读的权限。            channel.register(this.selector, SelectionKey.OP_READ);            System.err.println("客户端connect： " +count++);        } catch (ClosedChannelException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }    /**     * 处理读取服务端发来的信息 的事件s    */    public void read(SelectionKey key) throws IOException {        SocketChannel channel = (SocketChannel) key.channel();        channel.configureBlocking(false);        ByteBuffer buffer = ByteBuffer.allocate(100);        channel.read(buffer);        byte[] array = buffer.array();        String msg = new String(array).trim();        System.err.println("客户端read: " + msg + "  " +count++);        channel.register(this.selector, SelectionKey.OP_WRITE);    }}

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