Netty入门

Netty简介

Netty是一个提供异步事件驱动的网络应用框架，用以快速开发高性能、高可靠性的网络服务器和客户端程序。

换句话说，Netty是一个NIO框架，使用它可以简单快速地开发网络应用程序，比如客户端和服务端的协议。Netty大大简化了网络程序的开发过程比如TCP和UDP的 Socket的开发。

为什么选择Netty？

和NIO比较，要实现一个通信要简单得很多，性能很好。分布式消息中间件、storm、Dubble都是使用Netty作为底层通信。

Netty5.0要求jdk1.6以上。

http://netty.io

编码步骤

1. 创建两个N　　io线程组，一个事件处理（接收客户端连接），一个网络读写通信

2. 创建一个ServerBootStrap，配置Netty参数；

3. 创建实际处理的ChannelInitializer，进行初始化的准备工作，比如设置接收传出的字符集，格式，已经实际处理数据接口

4. 绑定端口执行同步阻塞方法等待服务器端启动。

详细介绍参照Netty 5用户指南： http://ifeve.com/netty5-user-guide

代码示例：

public class Server {

    public static void main(String[] args) throws Exception {
        //1 创建线两个程组 
        //一个是用于处理服务器端接收客户端连接的
        //一个是进行网络通信的（网络读写的）
        EventLoopGroup pGroup = new NioEventLoopGroup();
        EventLoopGroup cGroup = new NioEventLoopGroup();
        
        //2 创建辅助工具类，用于服务器通道的一系列配置
        ServerBootstrap b = new ServerBootstrap();
        b.group(pGroup, cGroup)        //绑定俩个线程组
        .channel(NioServerSocketChannel.class)        //指定NIO的模式
        .option(ChannelOption.SO_BACKLOG, 1024)        //设置tcp缓冲区
        .option(ChannelOption.SO_SNDBUF, 32*1024)    //设置发送缓冲大小
        .option(ChannelOption.SO_RCVBUF, 32*1024)    //这是接收缓冲大小
        .option(ChannelOption.SO_KEEPALIVE, true)    //保持连接
        .childHandler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel sc) throws Exception {
                //3 在这里配置具体数据接收方法的处理
                sc.pipeline().addLast(new ServerHandler());
            }
        });
        
        //4 进行绑定 
        ChannelFuture cf1 = b.bind(8765).sync();
        //ChannelFuture cf2 = b.bind(8764).sync();
        //5 等待关闭
        cf1.channel().closeFuture().sync();
        //cf2.channel().closeFuture().sync();
        pGroup.shutdownGracefully();
        cGroup.shutdownGracefully();
    }
}


public class ServerHandler extends ChannelHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("server channel active... ");
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req, "utf-8");
        System.out.println("Server :" + body);
        String response = "进行返回给客户端的响应：" + body;
        ctx.writeAndFlush(Unpooled.copiedBuffer(response.getBytes()));
        // .addListener(ChannelFutureListener.CLOSE); //发送完后关闭通道
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        System.out.println("读完了");
        ctx.flush();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable t) throws Exception {
        ctx.close();
    }

}


public class Client {

    public static void main(String[] args) throws Exception {

        EventLoopGroup group = new NioEventLoopGroup();
        Bootstrap b = new Bootstrap();
        b.group(group).channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel sc) throws Exception {
                sc.pipeline().addLast(new ClientHandler());
            }
        });

        ChannelFuture cf1 = b.connect("127.0.0.1", 8765).sync();
        // ChannelFuture cf2 = b.connect("127.0.0.1", 8764).sync();
        // 发送消息
        Thread.sleep(1000);
        cf1.channel().writeAndFlush(Unpooled.copiedBuffer("777".getBytes()));
        cf1.channel().writeAndFlush(Unpooled.copiedBuffer("666".getBytes()));
        // cf2.channel().writeAndFlush(Unpooled.copiedBuffer("888".getBytes()));
        Thread.sleep(2000);
        cf1.channel().writeAndFlush(Unpooled.copiedBuffer("888".getBytes()));
        // cf2.channel().writeAndFlush(Unpooled.copiedBuffer("666".getBytes()));

        cf1.channel().closeFuture().sync();
        // cf2.channel().closeFuture().sync();
        group.shutdownGracefully();
    }
}


public class ClientHandler extends ChannelHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        try {
            ByteBuf buf = (ByteBuf) msg;

            byte[] req = new byte[buf.readableBytes()];
            buf.readBytes(req);

            String body = new String(req, "utf-8");
            System.out.println("Client :" + body);
        } finally {
            // 缓存区需要及时清理，如果有写的方法，则不用清理。因为write方法帮我们做了清理
            ReferenceCountUtil.release(msg);
        }
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {

    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        ctx.close();
    }

}

netty的tcp拆包粘包问题

定长方案代码示例：FixedLengthFrameDecoder

public class Server {

    public static void main(String[] args) throws Exception {
        // 1 创建2个线程，一个是负责接收客户端的连接。一个是负责进行数据传输的
        EventLoopGroup pGroup = new NioEventLoopGroup();
        EventLoopGroup cGroup = new NioEventLoopGroup();

        // 2 创建服务器辅助类
        ServerBootstrap b = new ServerBootstrap();
        b.group(pGroup, cGroup).channel(NioServerSocketChannel.class).option(ChannelOption.SO_BACKLOG, 1024)
                .option(ChannelOption.SO_SNDBUF, 32 * 1024).option(ChannelOption.SO_RCVBUF, 32 * 1024)
                .childHandler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel sc) throws Exception {
                        // 设置定长字符串接收
                        sc.pipeline().addLast(new FixedLengthFrameDecoder(5));
                        // 设置字符串形式的解码
                        sc.pipeline().addLast(new StringDecoder());
                        sc.pipeline().addLast(new ServerHandler());
                    }
                });

        // 4 绑定连接
        ChannelFuture cf = b.bind(8765).sync();

        // 等待服务器监听端口关闭
        cf.channel().closeFuture().sync();
        pGroup.shutdownGracefully();
        cGroup.shutdownGracefully();
    }
}


public class ServerHandler extends ChannelHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(" server channel active... ");
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        String request = (String) msg;
        System.out.println("Server :" + msg);
        String response = request;
        ctx.writeAndFlush(Unpooled.copiedBuffer(response.getBytes()));
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {

    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable t) throws Exception {

    }

}


public class Client {

    public static void main(String[] args) throws Exception {

        EventLoopGroup group = new NioEventLoopGroup();

        Bootstrap b = new Bootstrap();
        b.group(group).channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel sc) throws Exception {
                sc.pipeline().addLast(new FixedLengthFrameDecoder(5));
                sc.pipeline().addLast(new StringDecoder());
                sc.pipeline().addLast(new ClientHandler());
            }
        });

        ChannelFuture cf = b.connect("127.0.0.1", 8765).sync();

        cf.channel().writeAndFlush(Unpooled.wrappedBuffer("aaaaabbbbb".getBytes()));
        cf.channel().writeAndFlush(Unpooled.copiedBuffer("ccccccc".getBytes()));
        cf.channel().writeAndFlush(Unpooled.copiedBuffer("ddddd   ".getBytes()));
        // 等待客户端端口关闭
        cf.channel().closeFuture().sync();
        group.shutdownGracefully();

    }
}


public class ClientHandler extends ChannelHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("client channel active... ");
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        String response = (String) msg;
        System.out.println("Client: " + response);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
    }

}

分隔符方案代码示例：DelimiterBasedFrameDecoder

public class Server {
    public static void main(String[] args) throws Exception {
        // 1 创建2个线程，一个是负责接收客户端的连接。一个是负责进行数据传输的
        EventLoopGroup pGroup = new NioEventLoopGroup();
        EventLoopGroup cGroup = new NioEventLoopGroup();

        // 2 创建服务器辅助类
        ServerBootstrap b = new ServerBootstrap();
        b.group(pGroup, cGroup).channel(NioServerSocketChannel.class).option(ChannelOption.SO_BACKLOG, 1024)
                .option(ChannelOption.SO_SNDBUF, 32 * 1024).option(ChannelOption.SO_RCVBUF, 32 * 1024)
                .childHandler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel sc) throws Exception {
                        // 设置特殊分隔符
                        ByteBuf buf = Unpooled.copiedBuffer("$_".getBytes());
                        sc.pipeline().addLast(new DelimiterBasedFrameDecoder(1024, buf));
                        // 设置字符串形式的解码
                        sc.pipeline().addLast(new StringDecoder());
                        sc.pipeline().addLast(new ServerHandler());
                    }
                });

        // 4 绑定连接
        ChannelFuture cf = b.bind(8765).sync();

        // 等待服务器监听端口关闭
        cf.channel().closeFuture().sync();
        pGroup.shutdownGracefully();
        cGroup.shutdownGracefully();

    }

}


public class ServerHandler extends ChannelHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(" server channel active... ");
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        String request = (String) msg;
        System.out.println("Server :" + msg);
        String response = "服务器响应：" + msg + "$_";
        ctx.writeAndFlush(Unpooled.copiedBuffer(response.getBytes()));
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {

    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable t) throws Exception {
        ctx.close();
    }

}


public class Client {

    public static void main(String[] args) throws Exception {

        EventLoopGroup group = new NioEventLoopGroup();

        Bootstrap b = new Bootstrap();
        b.group(group).channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel sc) throws Exception {
                //
                ByteBuf buf = Unpooled.copiedBuffer("$_".getBytes());
                sc.pipeline().addLast(new DelimiterBasedFrameDecoder(1024, buf));
                sc.pipeline().addLast(new StringDecoder());
                sc.pipeline().addLast(new ClientHandler());
            }
        });

        ChannelFuture cf = b.connect("127.0.0.1", 8765).sync();

        cf.channel().writeAndFlush(Unpooled.wrappedBuffer("bbbb$_".getBytes()));
        cf.channel().writeAndFlush(Unpooled.wrappedBuffer("cccc$_".getBytes()));

        // 等待客户端端口关闭
        cf.channel().closeFuture().sync();
        group.shutdownGracefully();

    }
}


public class ClientHandler extends ChannelHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("client channel active... ");
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        try {
            String response = (String) msg;
            System.out.println("Client: " + response);
        } finally {
            ReferenceCountUtil.release(msg);
        }
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        ctx.close();
    }

}

自定义方案:

http://blog.csdn.net/zbw18297786698/article/details/53691915