java nio Channel的使用

Channel是nio包的一个抽象类，作为java nio的三大组件（Buffer、Channel，Selector）之一，在java nio网络编程中尤为重要。

Channel是读写数据的双向通道，可以从Channel将数据读取Buffer,也可将Buffer的数据写入Channel。我们这里主要讨论用于网络编程的ServerSocketChannel，SocketChannel，DatagramChannel。

本文档需要使用Buffer操作，Buffer的使用可参考：http://t.csdn.cn/f1ZB9。

服务端

public class Server {
    public static void main(String[] args) throws IOException {
        //创建服务端Channel
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        //服务端channel监听8080端口
        serverSocketChannel.bind(new InetSocketAddress(8080));

        while (true){
            //阻塞等待tcp客户端连接
            SocketChannel channel = serverSocketChannel.accept();

            InetSocketAddress remoteAddress = (InetSocketAddress) channel.getRemoteAddress();
            System.out.println("客户端信息："+remoteAddress.getAddress().getHostAddress()+" "+remoteAddress.getPort());

            //处理客户端channel消息读写操作
            handleMsg(channel);
        }
    }

    
    public static void handleMsg(SocketChannel channel){
        new Thread(()->{
            //创建大小为100的字节缓冲区，用于配合Channel读写操作
            ByteBuffer buffer = ByteBuffer.allocate(100);
            try {
                while (true){
                    //阻塞等待接收已连接的tcp客户端数据
                    int readCount = channel.read(buffer);
                    if(readCount<=0){
                        channel.close();
                        break;
                    }

                    //limit = position;position = 0;
                    buffer.flip();
                    //mark = position;(记录position位置)
                    buffer.mark();

                    System.out.println("接收到字节数据：");
                    while (buffer.position()
                        System.out.print(buffer.get()+" ");
                    }
                    System.out.println();

                    //position = mark;(将记录的position位置恢复)
                    buffer.reset();
                    //向tcp客户端写数据
                    channel.write(buffer);
                    buffer.clear();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }finally {
                closeIO(channel);
            }

        }).start();
    }

    //关闭流方法
    private static void closeIO(Closeable io){
        if(io!=null){
            try{
                io.close();
            }catch (IOException e){
                e.printStackTrace();
            }
        }
    }
}

客户端

public class Client {
    public static void main(String[] args) throws IOException {
        //创建客户端Channel
        SocketChannel channel = SocketChannel.open();
        //指定服务端ip、port进行连接
        channel.connect(new InetSocketAddress("127.0.0.1",8080));

        //接收服务端写入数据
        handleMsg(channel);

        Scanner scanner = new Scanner(System.in);
        while (true){
            String str = scanner.next();
            if("exit".equals(str)){
                break;
            }
            ByteBuffer buffer = ByteBuffer.wrap(str.getBytes());
            channel.write(buffer);
        }
        
        closeIO(channel);
    }

    
    public static void handleMsg(SocketChannel channel) {
        new Thread(()->{
            //创建大小为100的字节缓冲区，用于配合Channel读写操作
            ByteBuffer buffer = ByteBuffer.allocate(100);
            try {
                while (true){
                    //阻塞等待接收tcp服务端数据
                    int readCount = channel.read(buffer);
                    if(readCount<=0){
                        channel.close();
                        break;
                    }

                    //limit = position;position = 0;
                    buffer.flip();

                    System.out.println("接收到数据：");
                    while (buffer.position()
                        System.out.print(buffer.get()+" ");
                    }
                    System.out.println();

                    //position = 0;limit = capacity;mark = -1;
                    buffer.clear();
                }
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                closeIO(channel);
            }
        }).start();
    }

    //关闭流方法
    private static void closeIO(Closeable io){
        if(io!=null){
            try{
                io.close();
            }catch (IOException e){
                e.printStackTrace();
            }
        }
    }
}

ServerSocketChannel（部分代码）

//创建服务端Channel
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
//服务端channel监听8080端口
serverSocketChannel.bind(new InetSocketAddress(8080));

//将ServerSocketChannel设置为非阻塞模式
serverSocketChannel.configureBlocking(false);

SocketChannel channel = serverSocketChannel.accept();

SocketChannel（部分代码）

//创建客户端Channel
SocketChannel channel = SocketChannel.open();
//指定服务端ip、port进行连接
channel.connect(new InetSocketAddress("127.0.0.1",8080));
//创建大小为100的字节缓冲区，用于配合Channel读写操作
ByteBuffer buffer = ByteBuffer.allocate(100);


channel.configureBlocking(false);
int readCount = channel.read(buffer);