NIO与Socket

Posted 2021-01-20 chen--biao

一、Socket 的使用

　　1、单线程Socket的使用　　　　

/**
 * 单线程版本
 * 问题描述：只能服务单个客户端
 * 解决方案：多线程版本
 */
public class Socket_V1 {
	public static void main(String[] args) throws Exception {
		ServerSocket serverSocket = new ServerSocket(1234);
		System.out.println("启动服务器：");
		while(true) {
			System.out.println("等待客户端链接（阻塞）……");
			Socket socket = serverSocket.accept();
			System.out.println("有链接进来了……");
			handle(socket);
		}
	}
	private static void handle(Socket socket) {
		try {
			InputStream inputStream = socket.getInputStream();
			byte[] b = new byte[1024];
			String str = null;
			while(true) {
				str = null;
				System.out.println("等待输入……");
				int read = inputStream.read(b);
				if(read == -1) {
					System.out.println("客户端关闭。");
					break;
				}
				str = new String(b);
				System.out.println(str);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

　　2、多线程版本

/**
 * 多线程版本
 * 问题描述：多线程开销大
 * 解决方案：NIO
 */
public class Socket_V2 {

	public static void main(String[] args) throws Exception {
		ServerSocket serverSocket = new ServerSocket(1234);
		// 创建一个定长线程池，可控制线程最大并发数，超出的线程会在队列中等待。
		ExecutorService threadPool = Executors.newFixedThreadPool(10);
		System.out.println("启动服务器：");
		while(true) {
			System.out.println("等待客户端链接（阻塞）……");
			final Socket socket = serverSocket.accept();
			System.out.println("有链接进来了……");
			//使用线程池来，支持并发
			threadPool.execute(new Runnable() {
				public void run() {
					handle(socket);
				}
			});
		}
	}
	private static void handle(Socket socket) {
		try {
			InputStream inputStream = socket.getInputStream();
			byte[] b = new byte[1024];
			String str = null;
			while(true) {
				str = null;
				System.out.println("等待输入……");
				int read = inputStream.read(b);
				if(read == -1) {
					System.out.println("客户端关闭。");
					break;
				}
				str = new String(b);
				System.out.println(str);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

　　3、NIO 

/**
 * NIO版本
 * 原理：IO多路复用
 * NIO与旧Socket对比：
 * 	ServerSocketChannel	<-等价于->	ServerSocket
 * 	SocketChannel		<-等价于->	Socket
 * 	Selector   		选择器
 * 	SelectionKey 	事件类型
 */
public class Socket_NIO {
	public static void main(String[] args) throws Exception {
		//获得Socket通道
		ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
		//将通道设置为非阻塞模式
		serverSocketChannel.configureBlocking(false);
		//将通道绑定到指定的端口
		serverSocketChannel.socket().bind(new InetSocketAddress(1234));
		//获取通道选择器
		Selector selector = Selector.open();
		//将连接事件，注册到选择器内（步骤1）
		serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
		System.out.println("服务器启动成功。端口已经监听……");
		while(true) {
			selector.select();//阻塞等待已经注册的事件
			Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
			while(iterator.hasNext()) {
				SelectionKey next = iterator.next();
				iterator.remove();
				if(next.isAcceptable()) { //如果是连接事件,注册读写事件
					System.out.println("获取到连接事件。");
					ServerSocketChannel sschannel = (ServerSocketChannel) next.channel();  //该强转是步骤1内存放的值
					SocketChannel channel = sschannel.accept(); //获取客户端连接的通道
					channel.configureBlocking(false);//设置为非阻塞
					channel.register(selector, SelectionKey.OP_READ); //步骤2
				}else if(next.isReadable()) { //如果是可读事件，则执行读操作
					System.out.println("获取到可读事件。");
					SocketChannel channel = (SocketChannel) next.channel(); //获取socket通道，该强转是步骤2内存放的值
					ByteBuffer dst = ByteBuffer.allocate(1024); //缓冲区
					int read = channel.read(dst);
					if(read < 0 ) {
						System.out.println("客户端关闭。");
						next.cancel();
						break;
					}
					System.out.println("客户端输入："+new String(dst.array()));
				} //还有其他事件……略
			}
		}
	}
}