netty

时间 2019-12-05

标签 netty 栏目 Netty 繁體版

原文原文链接

netty

概念: Netty是由JBOSS提供的一个java开源框架。Netty提供异步的、事件驱动的网络应用程序框架和工具，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。
也就是说，Netty 是一个基于NIO的客户、服务器端编程框架，使用Netty 能够确保你快速和简单的开发出一个网络应用，例如实现了某种协议的客户，服务端应用。Netty至关简化和流线化了网络应用的编程开发过程，例如，TCP和UDP的socket服务开发。java

新特性

处理大容量数据流更简单
处理协议编码和单元测试更简单
I/O超时和idle状态检测
应用程序的关闭更简单，更安全
更可靠的OutOfMemoryError预防

性能

更好的吞吐量，更低的延迟
更少的资源消耗
最小化没必要要的内存拷贝

具体使用见代码及注释

Helloword版
服务端这边绑定了两个端口，能够根据业务区别对待如端口1是作A业务，端2作B业务.编程

public class Server {
    public static void main(String[] args) throws InterruptedException {
        //1.建立两个线程组 (只有服务器端须要 )
        //一个线程组专门用来管理接收客户端的请求链接的
        //一个线程组进行网络通讯(读写)
        EventLoopGroup receiveGroup = new NioEventLoopGroup();
        EventLoopGroup dealGroup = new NioEventLoopGroup();
        //建立辅助工具类，用于设置服务器通道的一系列配置
        ServerBootstrap serverBootstrap = new ServerBootstrap();
        serverBootstrap.group(receiveGroup, dealGroup)//绑定两个线程组
        .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) //设置发送缓冲区大小
        .option(ChannelOption.SO_RCVBUF, 32*1024) //设置接收缓冲大小
        .option(ChannelOption.SO_KEEPALIVE, true)  //保持链接
        .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 = serverBootstrap.bind(8765).sync();
                ChannelFuture cf2 = serverBootstrap.bind(8764).sync();
                //5 等待关闭
                cf1.channel().closeFuture().sync();
                cf2.channel().closeFuture().sync();
                receiveGroup.shutdownGracefully();
                dealGroup.shutdownGracefully();
     }
}

服务端处理器:安全

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, "gbk");
            System.out.println("Server :" + body );
            String response = "进行返回给客户端的响应：" + body ;
            //注意使用了writeAndFlush的话就能够不释放ReferenceCountUtil.release(msg); 不然须要释放ByteBuf容器的数据。
            ctx.writeAndFlush(Unpooled.copiedBuffer(response.getBytes()));
            //.addListener(ChannelFutureListener.CLOSE);//监听，内容传输完毕后就关闭管道
    }

    @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();
    }


}

客户端:服务器

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
        cf1.channel().writeAndFlush(Unpooled.copiedBuffer("C1：777".getBytes()));
        Thread.sleep(1000);
        cf1.channel().writeAndFlush(Unpooled.copiedBuffer("C1:666".getBytes()));
        cf2.channel().writeAndFlush(Unpooled.copiedBuffer("C2:888".getBytes()));
        Thread.sleep(2000);
        cf1.channel().writeAndFlush(Unpooled.copiedBuffer("C1:888".getBytes()));
        cf2.channel().writeAndFlush(Unpooled.copiedBuffer("C2:666".getBytes()));
        
        cf1.channel().closeFuture().sync();
        cf2.channel().closeFuture().sync();
        group.shutdownGracefully();
        
        
        
    }
}

客户端处理器：网络

public class ClientHandler extends ChannelHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("客户端的channelActive()方法");
    }

    @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, "gbk");
            System.out.println("Client :" + body );
        } finally {
            ReferenceCountUtil.release(msg);
        }
    }

TCP拆包粘包问题

TCP是个“流”协议，所谓流，就是没有界限的一串数据。你们能够想一想河里的流水，是连成一片的，其间并无分界线。TCP底层并不了解上层业务数据的具体含义，它会根据TCP缓冲区的实际状况进行包的划分，因此在业务上认为，一个完整的包可能会被TCP拆分红多个包进行发送，也有可能把多个小的包封装成一个大的数据包发送，这就是所谓的TCP粘包和拆包问题。
通俗意义来讲多是三个数据如'A','B','C' 但通过TCP协议流式传输后成了'AB','C'两个数据了,这种就是粘包了数据包之间粘一块儿了。那么拆包的话有三种方式。app

设置每一个数据包的大小如200个字节，若是某个数据包不足200个字节可能会出现丢包的状况，即该数据包未从一个端到另外一个端，此时须要用空格或者既定的符号补充.
在数据包之间使用一些字符进行分割如$号之类的，解析的时候先处理掉分隔符再拿到各个数据包就行了。(通常用的比较多)
细粒化数据包分为头和尾(将消息分为消息头和消息尾)
其余

两根水管（服务器与客户端）须要相互流通水(数据)，那么须要一个转接头(套接字)链接，水流式没法区分一段段的数据，一种方式在流通的过程当中设置些标志性物品如记号笔勾一下(分隔符)，另外一种方式则是设定每一段都是多少容量的水来区分.框架

使用分隔符解决TCP粘包

能够理解管道流里流的都是ByteBuffer类型的数据，那么使用分隔符(非ByteBuffer类型)的话可能就意味着一个转码与解码的过程。
服务端:异步

public class Server {
    public static void main(String[] args) throws Exception{
        //1 建立2个线程，一个是负责接收客户端的链接。一个是负责进行数据传输的
        EventLoopGroup pGroup = new NioEventLoopGroup();
        EventLoopGroup cGroup = new NioEventLoopGroup();
        
        //2 建立服务器辅助类
        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  解决TCP拆包黏包问题，
                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 绑定链接
        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();
        
    }
}

服务端处理器:socket

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 channelRead:" + request);
        String response = "服务器响应：" + msg + "$";
        ctx.writeAndFlush(Unpooled.copiedBuffer(response.getBytes()));
    }

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

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

}

客户端：tcp

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("数据A$".getBytes()));
        cf.channel().writeAndFlush(Unpooled.wrappedBuffer("数据B$".getBytes()));
        
        
        //等待客户端端口关闭
        cf.channel().closeFuture().sync();
        group.shutdownGracefully();
        
    }
}

客户端处理器:

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 {
        System.out.println("channelReadComplete");
    }

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

}

设置长度大小解决TCP拆包黏包问题

服务端:

public class Server {

    public static void main(String[] args) throws Exception{
        //1 建立2个线程，一个是负责接收客户端的链接。一个是负责进行数据传输的
        EventLoopGroup pGroup = new NioEventLoopGroup();
        EventLoopGroup cGroup = new NioEventLoopGroup();
        
        //2 建立服务器辅助类
        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 绑定链接
        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();
        
    }
    
}

客户端:

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

服务端与客户端的处理器参照上例以字符串分割的.

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