Netty实例几则

Netty是基于JDK NIO的网络框架

简化了NIO编程, 不用程序自己维护selector, 将网络通信和数据处理的部分做了分离

多用于做底层的数据通信, 心跳检测(keepalived)

1. 数据通信

1.1 Hello World

public class Server {

    public static void main(String[] args) throws Exception {
        // 1 创建线两个事件循环组
        // 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ServerBootstrap，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.NioServerSocketChannel对应TCP, NioDatagramChannel对应UDP
                .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 {  //SocketChannel建立连接后的管道
                        // 3 在这里配置 通信数据的处理逻辑, 可以addLast多个...
                        sc.pipeline().addLast(new ServerHandler());
                    }
                });

        // 4 绑定端口, bind返回future(异步), 加上sync阻塞在获取连接处
        ChannelFuture cf1 = b.bind(8765).sync();
        //ChannelFuture cf2 = b.bind(8764).sync();   //可以绑定多个端口
        // 5 等待关闭, 加上sync阻塞在关闭请求处
        cf1.channel().closeFuture().sync();
        //cf2.channel().closeFuture().sync();
        pGroup.shutdownGracefully();
        cGroup.shutdownGracefully();
    }
}

SO_BACKLOG详解:
服务器的TCP内核维护两个队列A和B
客户端向服务端请求connect时, 发送SYN(第一次握手)
服务端收到SYN后, 向客户端发送SYN ACK(第二次握手),  TCP内核将连接放入队列A
客户端收到后向服务端发送ACK(第三次握手),  TCP内核将连接从A->B, accept返回, 连接完成
A/B队列的长度和即为BACKLOG, 当accept速度跟不上, A/B队列使得BACKLOG满了, 客户端连接就会被TCP内核拒绝
可以调大backlog缓解这一现象, 经验值~100

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 = "返回给客户端的响应：" + body ;
            ctx.writeAndFlush(Unpooled.copiedBuffer(response.getBytes()));
            // future完成后触发监听器, 此处是写完即关闭(短连接). 因此需要关闭连接时, 要通过server端关闭. 直接关闭用方法ctx[.channel()].close()
            //.addListener(ChannelFutureListener.CLOSE);
    }

    @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();  //可以使用多个端口
        //发送消息, Buffer类型. write需要flush才发送, 可用writeFlush代替
        cf1.channel().writeAndFlush(Unpooled.copiedBuffer("777".getBytes()));
        cf1.channel().writeAndFlush(Unpooled.copiedBuffer("666".getBytes()));
        Thread.sleep(2000);
        cf1.channel().writeAndFlush(Unpooled.copiedBuffer("888".getBytes()));
        //cf2.channel().writeAndFlush(Unpooled.copiedBuffer("999".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 {
            // 记得释放xxxHandler里面的方法的msg参数: 写(write)数据, msg引用将被自动释放不用手动处理; 但只读数据时,!必须手动释放引用数
             ReferenceCountUtil.release(msg);
        }
    }

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

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

1.2 拆包粘包问题

TCP/IP确保了包的传送, 包的顺序等, 但编程中还需要解决拆包粘包问题

-> 接收的一连串包中的数据, 处理的分隔在哪里?  基本解决方案:

1)特殊字符作为结束分隔符

2)消息定长. 固定包的长度, 长度不够用空格补全. 接收方需要trim, 效率不高不推荐

3)自定义协议. 在消息头中包含消息总长度的字段. 需要安全性时可以考虑.

特殊字符

public class Server {

    public static void main(String[] args) throws Exception {
        EventLoopGroup pGroup = new NioEventLoopGroup();
        EventLoopGroup cGroup = new NioEventLoopGroup();
        
        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 {
                // 使用DelimiterBasedFrameDecoder设置结尾分隔符$_
                ByteBuf buf = Unpooled.copiedBuffer("$_".getBytes());
                sc.pipeline().addLast(new DelimiterBasedFrameDecoder(1024, buf));
                // 设置字符串形式的解码.  经过StringDecoder, Handler回调方法中接收的msg的具体类型就是String了(不再是ByteBuffer). 但写时仍需要传入ByteBuffer
                sc.pipeline().addLast(new StringDecoder());
                // 通信数据的处理逻辑
                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 {
        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()));
        
        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();
    }
}

定长

public class Server {

    public static void main(String[] args) throws Exception{
        EventLoopGroup pGroup = new NioEventLoopGroup();
        EventLoopGroup cGroup = new NioEventLoopGroup();
        
        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, 定长为5, 积累到5个字节才会把数据发出去
                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());
            }
        });
        
        ChannelFuture cf = b.bind(8765).sync();
        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("aaa".getBytes()));
        cf.channel().writeAndFlush(Unpooled.copiedBuffer("bbccccc".getBytes()));
        
        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 {
    }
}

1.3 编解码

即对象序列化技术, 目的是为了实现对象的网络传输和本地持久化
如果使用java的序列化, 码流较大. 因此多用Marshalling, Kyro(基于Protobuf)

下面的例子, 使用编解码传输javabean(Marshalling的javabean需要实现serializable), 并将message进行gzip压缩

自定义编解码器

public final class MarshallingCodeCFactory {
    // 解码
    public static MarshallingDecoder buildMarshallingDecoder() {
        //创建工厂对象, 参数serial指创建的是java对象序列化的工厂对象
        final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
        //创建配置对象，版本号为5 
        final MarshallingConfiguration configuration = new MarshallingConfiguration();
        configuration.setVersion(5);
        //根据工厂对象和配置对象创建解码provider
        UnmarshallerProvider provider = new DefaultUnmarshallerProvider(marshallerFactory, configuration);
        //创建解码器对象. 第一个参数是provider, 第二个参数是单个消息序列化后的最大长度, 超过后拒绝处理
        MarshallingDecoder decoder = new MarshallingDecoder(provider, 1024 * 1024 * 1);
        return decoder;
    }

    // 编码
    public static MarshallingEncoder buildMarshallingEncoder() {
        final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
        final MarshallingConfiguration configuration = new MarshallingConfiguration();
        configuration.setVersion(5);
        MarshallerProvider provider = new DefaultMarshallerProvider(marshallerFactory, configuration);
        //创建编码器对象. 用于将实现Serializable接口的JavaBean序列化为二进制数组
        MarshallingEncoder encoder = new MarshallingEncoder(provider);
        return encoder;
    }
}

javabean

public class Request implements Serializable {  // 标记Serializable接口

    private String id ;
    private String name ;
    private String requestMessage ;
    private byte[] attachment;
    
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getRequestMessage() {
        return requestMessage;
    }
    public void setRequestMessage(String requestMessage) {
        this.requestMessage = requestMessage;
    }
    public byte[] getAttachment() {
        return attachment;
    }
    public void setAttachment(byte[] attachment) {
        this.attachment = attachment;
    }
}

public class Response implements Serializable { // 标记Serializable接口
    
    private String id;
    private String name;
    private String responseMessage;
    
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getResponseMessage() {
        return responseMessage;
    }
    public void setResponseMessage(String responseMessage) {
        this.responseMessage = responseMessage;
    }
}

GZip压缩的Util

public class GzipUtils {

    public static byte[] gzip(byte[] data) throws Exception {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        GZIPOutputStream gzip = new GZIPOutputStream(bos);
        gzip.write(data);
        gzip.finish();
        gzip.close();
        byte[] ret = bos.toByteArray();
        bos.close();
        return ret;
    }
    
    public static byte[] ungzip(byte[] data) throws Exception{
        ByteArrayInputStream bis = new ByteArrayInputStream(data);
        GZIPInputStream gzip = new GZIPInputStream(bis);
        byte[] buf = new byte[1024];
        int num = -1;
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        while((num = gzip.read(buf)) != -1 ){
            bos.write(buf, 0, num);
        }
        gzip.close();
        bis.close();
        byte[] ret = bos.toByteArray();
        bos.close();
        return ret;
    }
}

服务端与客户端

public class Server {
    public static void main(String[] args) throws Exception{
        
        EventLoopGroup pGroup = new NioEventLoopGroup();
        EventLoopGroup cGroup = new NioEventLoopGroup();
        
        ServerBootstrap b = new ServerBootstrap();
        b.group(pGroup, cGroup)
         .channel(NioServerSocketChannel.class)
         .option(ChannelOption.SO_BACKLOG, 1024)
         //设置日志
         .handler(new LoggingHandler(LogLevel.INFO))
         .childHandler(new ChannelInitializer<SocketChannel>() {
            protected void initChannel(SocketChannel sc) throws Exception {
                // 添加编解码. 发送自定义的类型, 而Handler的方法接收的msg参数的实际类型也是相应的自定义类了
                sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());
                sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
                sc.pipeline().addLast(new ServerHandler());
            }
        });
        
        ChannelFuture cf = b.bind(8765).sync();
        cf.channel().closeFuture().sync();
        pGroup.shutdownGracefully();
        cGroup.shutdownGracefully();
    }

public class ServerHandler extends ChannelHandlerAdapter{

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

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        Request req = (Request)msg;
        System.out.println("Server : " + req.getId() + ", " + req.getName() + ", " + req.getRequestMessage());
        byte[] attachment = GzipUtils.ungzip(req.getAttachment());
        
        String path = System.getProperty("user.dir") + File.separatorChar + "receive" +  File.separatorChar + "001.jpg";
        FileOutputStream fos = new FileOutputStream(path);
        fos.write(attachment);
        fos.close();
        
        Response resp = new Response();
        resp.setId(req.getId());
        resp.setName("resp" + req.getId());
        resp.setResponseMessage("响应内容" + req.getId());
        ctx.writeAndFlush(resp);//.addListener(ChannelFutureListener.CLOSE);
    }

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

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) 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(MarshallingCodeCFactory.buildMarshallingDecoder());
                sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
                sc.pipeline().addLast(new ClientHandler());
            }
        });
        
        ChannelFuture cf = b.connect("127.0.0.1", 8765).sync();
        
        for(int i = 0; i < 5; i++){
            Request req = new Request();
            req.setId("" + i);
            req.setName("req" + i);
            req.setRequestMessage("数据信息" + i);    
            String path = System.getProperty("user.dir") + File.separatorChar + "sources" +  File.separatorChar + "001.jpg";
            File file = new File(path);
            FileInputStream in = new FileInputStream(file);  
            byte[] data = new byte[in.available()];  
            in.read(data);  
            in.close(); 
            req.setAttachment(GzipUtils.gzip(data)); //压缩
            cf.channel().writeAndFlush(req);
        }

        cf.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 {
            Response resp = (Response) msg;
            System.out.println("Client : " + resp.getId() + ", " + resp.getName() + ", " + resp.getResponseMessage());            
        } finally {
            ReferenceCountUtil.release(msg);
        }
    }

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

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

1.4 长连接/短连接

1.长连接, 一致保持着连接不主动中断, 实时性强
2.短连接. 数据放在缓存, 一次性批量提交所有数据, 服务端接收后即关闭连接
以上两种根据是否给ChannelHandlerContext添加ChannelFutureListener.ClOSE监听器实现

3.长连接, 一定时间不活跃则关闭连接. 给SocketChannel添加ReadTimeoutHandler实现. 实例如下:

public final class MarshallingCodeCFactory {
    public static MarshallingDecoder buildMarshallingDecoder() {
        final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
        final MarshallingConfiguration configuration = new MarshallingConfiguration();
        configuration.setVersion(5);
        UnmarshallerProvider provider = new DefaultUnmarshallerProvider(marshallerFactory, configuration);
        MarshallingDecoder decoder = new MarshallingDecoder(provider, 1024);
        return decoder;
    }
    public static MarshallingEncoder buildMarshallingEncoder() {
        final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
        final MarshallingConfiguration configuration = new MarshallingConfiguration();
        configuration.setVersion(5);
        MarshallerProvider provider = new DefaultMarshallerProvider(marshallerFactory, configuration);
        MarshallingEncoder encoder = new MarshallingEncoder(provider);
        return encoder;
    }
}

public class Request implements Serializable{
    private String id ;
    private String name ;
    private String requestMessage ;
    
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getRequestMessage() {
        return requestMessage;
    }
    public void setRequestMessage(String requestMessage) {
        this.requestMessage = requestMessage;
    }
}

public class Response implements Serializable{
    private String id;
    private String name;
    private String responseMessage;
    
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getResponseMessage() {
        return responseMessage;
    }
    public void setResponseMessage(String responseMessage) {
        this.responseMessage = responseMessage;
    }
}

public class Server {

    public static void main(String[] args) throws Exception{
        
        EventLoopGroup pGroup = new NioEventLoopGroup();
        EventLoopGroup cGroup = new NioEventLoopGroup();
        
        ServerBootstrap b = new ServerBootstrap();
        b.group(pGroup, cGroup)
         .channel(NioServerSocketChannel.class)
         .option(ChannelOption.SO_BACKLOG, 1024)
         //设置日志
         .handler(new LoggingHandler(LogLevel.INFO))
         .childHandler(new ChannelInitializer<SocketChannel>() {
            protected void initChannel(SocketChannel sc) throws Exception {
                sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());
                sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
                sc.pipeline().addLast(new ReadTimeoutHandler(5));  // 时限, 读客户端超时没数据则断开
                sc.pipeline().addLast(new ServerHandler());
            }
        });
        
        ChannelFuture cf = b.bind(8765).sync();
        cf.channel().closeFuture().sync();
        pGroup.shutdownGracefully();
        cGroup.shutdownGracefully();
    }
}

public class ServerHandler extends ChannelHandlerAdapter{

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

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        Request request = (Request) msg;
        System.out.println("Server : " + request.getId() + ", " + request.getName() + ", " + request.getRequestMessage());
        Response response = new Response();
        response.setId(request.getId());
        response.setName("response" + request.getId());
        response.setResponseMessage("响应内容" + request.getId());
        ctx.writeAndFlush(response);
    }

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

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

public class Client {
    private EventLoopGroup group;
    private Bootstrap b;
    private ChannelFuture cf ;

    // 单例
    private static class SingletonHolder { 
        static final Client instance = new Client();
    }
    public static Client getInstance(){
        return SingletonHolder.instance;
    }
    
    private Client(){
            group = new NioEventLoopGroup();
            b = new Bootstrap();
            b.group(group)
             .channel(NioSocketChannel.class)
             .handler(new LoggingHandler(LogLevel.INFO))
             .handler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel sc) throws Exception {
                        sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());
                        sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
                        //超时handler（当服务器端与客户端在指定时间以上没有任何进行通信，则会关闭通道）
                        sc.pipeline().addLast(new ReadTimeoutHandler(5));   // 时限5s, 读服务端超时没数据则断开
                        sc.pipeline().addLast(new ClientHandler());
                    }
            });
    }
    
    public void connect(){
        try {
            this.cf = b.connect("127.0.0.1", 8765).sync();
            System.out.println("远程服务器已经连接, 可以进行数据交换");                
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    public ChannelFuture getChannelFuture(){
        if(this.cf == null) {   //初次连接
            this.connect();
        }
        if(!this.cf.channel().isActive()){  //重连
            this.connect();
        }
        return this.cf;
    }
    
    public static void main(String[] args) throws Exception{
        final Client c = Client.getInstance();
        
        ChannelFuture cf = c.getChannelFuture();
        for(int i = 1; i <= 3; i++ ){
            Request request = new Request();
            request.setId("" + i);
            request.setName("request" + i);
            request.setRequestMessage("数据信息" + i);
            cf.channel().writeAndFlush(request);
            TimeUnit.SECONDS.sleep(4);  //间隔4s发送一次数据
        }

        cf.channel().closeFuture().sync(); //阻塞至超时关闭
        
        // 这里用子线程重连并发送数据一次
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    System.out.println("进入子线程重连一次");
                    ChannelFuture cf = c.getChannelFuture();
                    assert true == cf.channel().isActive(); //断言
                    //再次发送数据
                    Request request = new Request();
                    request.setId("" + 4);
                    request.setName("request" + 4);
                    request.setRequestMessage("数据信息" + 4);
                    cf.channel().writeAndFlush(request);                    
                    cf.channel().closeFuture().sync();
                    System.out.println("子线程完成");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }).start();
        
        System.out.println("断开连接,主线程结束..");
    }
    
}

public class ClientHandler extends ChannelHandlerAdapter{
    
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
    }

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

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

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

1.5 使用UDP (较少使用)

public class Server {
    public void run(int port) throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group).channel(NioDatagramChannel.class)  // UDP: NioDatagramChannel
                .option(ChannelOption.SO_BROADCAST, true) // 广播
                .handler(new ServerHandler());
            b.bind(port).sync().channel().closeFuture().await();
        } finally {
            group.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        new Server().run(8765);
    }
}

public class ServerHandler extends SimpleChannelInboundHandler<DatagramPacket> {

    // 谚语列表
    private static final String[] DICTIONARY = { 
        "只要功夫深，铁棒磨成针。",
        "旧时王谢堂前燕，飞入寻常百姓家。", 
        "洛阳亲友如相问，一片冰心在玉壶。",
        "一寸光阴一寸金，寸金难买寸光阴。",
        "老骥伏枥，志在千里。烈士暮年，壮心不已!"
    };

    private String nextQuote() {
        int quoteId = ThreadLocalRandom.current().nextInt(DICTIONARY.length);
        return DICTIONARY[quoteId];
    }

    @Override
    public void messageReceived(ChannelHandlerContext ctx, DatagramPacket packet) throws Exception {
        String req = packet.content().toString(CharsetUtil.UTF_8);
        System.out.println(req);
        if ("谚语字典查询?".equals(req)) {
            ctx.writeAndFlush(new DatagramPacket(Unpooled.copiedBuffer("谚语查询结果: " + nextQuote(), CharsetUtil.UTF_8), packet.sender()));
        }
    }

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

public class Client {

    public void run(int port) throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group).channel(NioDatagramChannel.class)
                .option(ChannelOption.SO_BROADCAST, true)
                .handler(new ClientHandler());
            Channel ch = b.bind(0).sync().channel();
            // 向网段内的所有机器广播UDP消息
            ch.writeAndFlush(new DatagramPacket(Unpooled.copiedBuffer("谚语字典查询?", CharsetUtil.UTF_8), new InetSocketAddress("255.255.255.255", port))).sync();
            if (!ch.closeFuture().await(15000)) {
                System.out.println("查询超时!");
            }
        } finally {
            group.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        new Client().run(8765);
    }
}

public class ClientHandler extends SimpleChannelInboundHandler<DatagramPacket> {

    @Override
    public void messageReceived(ChannelHandlerContext ctx, DatagramPacket msg) throws Exception {
        String response = msg.content().toString(CharsetUtil.UTF_8);
        if (response.startsWith("谚语查询结果: ")) {
            System.out.println(response);
            ctx.close();
        }
    }

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

2. 心跳检测

集群中主服务器需要知道从服务器的状态
因此client每隔5~10秒给server发送心跳包

可通过netty与定时任务来实现

public final class MarshallingCodeCFactory {
    public static MarshallingDecoder buildMarshallingDecoder() {
        final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
        final MarshallingConfiguration configuration = new MarshallingConfiguration();
        configuration.setVersion(5);
        UnmarshallerProvider provider = new DefaultUnmarshallerProvider(marshallerFactory, configuration);
        MarshallingDecoder decoder = new MarshallingDecoder(provider, 1024 * 1024 * 1);
        return decoder;
    }
    public static MarshallingEncoder buildMarshallingEncoder() {
        final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
        final MarshallingConfiguration configuration = new MarshallingConfiguration();
        configuration.setVersion(5);
        MarshallerProvider provider = new DefaultMarshallerProvider(marshallerFactory, configuration);
        MarshallingEncoder encoder = new MarshallingEncoder(provider);
        return encoder;
    }
}

public class RequestInfo implements Serializable {
    private String ip ;
    private HashMap<String, Object> cpuPercMap ;
    private HashMap<String, Object> memoryMap;
    
    public String getIp() {
        return ip;
    }
    public void setIp(String ip) {
        this.ip = ip;
    }
    public HashMap<String, Object> getCpuPercMap() {
        return cpuPercMap;
    }
    public void setCpuPercMap(HashMap<String, Object> cpuPercMap) {
        this.cpuPercMap = cpuPercMap;
    }
    public HashMap<String, Object> getMemoryMap() {
        return memoryMap;
    }
    public void setMemoryMap(HashMap<String, Object> memoryMap) {
        this.memoryMap = memoryMap;
    }
}

public class Server {

    public static void main(String[] args) throws Exception{
        
        EventLoopGroup pGroup = new NioEventLoopGroup();
        EventLoopGroup cGroup = new NioEventLoopGroup();
        
        ServerBootstrap b = new ServerBootstrap();
        b.group(pGroup, cGroup)
         .channel(NioServerSocketChannel.class)
         .option(ChannelOption.SO_BACKLOG, 1024)
         //设置日志
         .handler(new LoggingHandler(LogLevel.INFO))
         .childHandler(new ChannelInitializer<SocketChannel>() {
            protected void initChannel(SocketChannel sc) throws Exception {
                sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());
                sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
                sc.pipeline().addLast(new ServerHeartBeatHandler());
            }
        });
        
        ChannelFuture cf = b.bind(8765).sync();
        cf.channel().closeFuture().sync();
        pGroup.shutdownGracefully();
        cGroup.shutdownGracefully();
    }
}

public class ServerHeartBeatHandler extends ChannelHandlerAdapter {
    
    private static HashMap<String, String> AUTH_IP_MAP = new HashMap<String, String>();
    private static final String SUCCESS_KEY = "auth_success_key";
    
    static {
        AUTH_IP_MAP.put("127.0.0.1", "1234");
    }
    
    private boolean auth(ChannelHandlerContext ctx, Object msg){
        String [] ret = ((String) msg).split(",");
        String auth = AUTH_IP_MAP.get(ret[0]);
        if(auth != null && auth.equals(ret[1])){
            // 认证成功, 返回确认信息
            ctx.writeAndFlush(SUCCESS_KEY);
            return true;
        } else {
            ctx.writeAndFlush("auth failure !").addListener(ChannelFutureListener.CLOSE);
            return false;
        }
    }
    
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        if(msg instanceof String){
            auth(ctx, msg);
        } else if (msg instanceof RequestInfo) {
            RequestInfo info = (RequestInfo) msg;
            System.out.println("--------------------------------------------");
            System.out.println("当前主机ip为: " + info.getIp());
            System.out.println("当前主机cpu情况: ");
            HashMap<String, Object> cpu = info.getCpuPercMap();
            System.out.println("总使用率: " + cpu.get("combined"));
            System.out.println("用户使用率: " + cpu.get("user"));
            System.out.println("系统使用率: " + cpu.get("sys"));
            System.out.println("等待率: " + cpu.get("wait"));
            System.out.println("空闲率: " + cpu.get("idle"));
            
            System.out.println("当前主机memory情况: ");
            HashMap<String, Object> memory = info.getMemoryMap();
            System.out.println("内存总量: " + memory.get("total"));
            System.out.println("当前内存使用量: " + memory.get("used"));
            System.out.println("当前内存剩余量: " + memory.get("free"));
            System.out.println("--------------------------------------------");
            
            ctx.writeAndFlush("info received!");
        } else {
            ctx.writeAndFlush("connect failure!").addListener(ChannelFutureListener.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(MarshallingCodeCFactory.buildMarshallingDecoder());
                sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
                sc.pipeline().addLast(new ClienHeartBeatHandler());
            }
        });
        
        ChannelFuture cf = b.connect("127.0.0.1", 8765).sync();
        cf.channel().closeFuture().sync();
        group.shutdownGracefully();
    }
}

public class ClienHeartBeatHandler extends ChannelHandlerAdapter {

    private ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
    private ScheduledFuture<?> heartBeat;  //定时任务
    //主动向服务器发送认证信息
    private InetAddress addr ;
    private static final String SUCCESS_KEY = "auth_success_key";

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        addr = InetAddress.getLocalHost();
        //String ip = addr.getHostAddress();
        String ip = "127.0.0.1";
        String key = "1234";
        //证书
        String auth = ip + "," + key;
        // 发送认证
        ctx.writeAndFlush(auth);
    }
    
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        try {
            if(msg instanceof String){
                String ret = (String) msg;
                if(SUCCESS_KEY.equals(ret)){
                    // 收到认证 确认信息，设置每隔5秒发送心跳消息
                    this.heartBeat = this.scheduler.scheduleWithFixedDelay(new HeartBeatTask(ctx), 0, 5, TimeUnit.SECONDS);
                    System.out.println(msg);                
                } else {  
                    // 收到心跳包 确认信息
                    System.out.println(msg);
                }
            }
        } finally {
            // 只读, 需要手动释放引用计数
            ReferenceCountUtil.release(msg);
        }
    }

    private class HeartBeatTask implements Runnable {
        private final ChannelHandlerContext ctx;
        public HeartBeatTask(final ChannelHandlerContext ctx) {
            this.ctx = ctx;
        }
        @Override
        public void run() {
            try {
                RequestInfo info = new RequestInfo();
                //ip
                info.setIp(addr.getHostAddress());
                Sigar sigar = new Sigar();
                //cpu prec
                CpuPerc cpuPerc = sigar.getCpuPerc();
                HashMap<String, Object> cpuPercMap = new HashMap<String, Object>();
                cpuPercMap.put("combined", cpuPerc.getCombined());
                cpuPercMap.put("user", cpuPerc.getUser());
                cpuPercMap.put("sys", cpuPerc.getSys());
                cpuPercMap.put("wait", cpuPerc.getWait());
                cpuPercMap.put("idle", cpuPerc.getIdle());
                // memory
                Mem mem = sigar.getMem();
                HashMap<String, Object> memoryMap = new HashMap<String, Object>();
                memoryMap.put("total", mem.getTotal() / 1024L);
                memoryMap.put("used", mem.getUsed() / 1024L);
                memoryMap.put("free", mem.getFree() / 1024L);
                info.setCpuPercMap(cpuPercMap);
                info.setMemoryMap(memoryMap);
                
                ctx.writeAndFlush(info);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
            cause.printStackTrace();
            // 取消定时发送心跳包的任务
            if (heartBeat != null) {
                heartBeat.cancel(true);
                heartBeat = null;
            }
            ctx.fireExceptionCaught(cause);
        }
    }
}

3. HTTP

3.1 Hello World

public final class HttpHelloWorldServer {
  
      static final boolean SSL = System.getProperty("ssl") != null;
      static final int PORT = Integer.parseInt(System.getProperty("port", SSL? "8443" : "8080"));
  
      public static void main(String[] args) throws Exception {
          final SslContext sslCtx;
          if (SSL) {
              SelfSignedCertificate ssc = new SelfSignedCertificate();
              sslCtx = SslContext.newServerContext(ssc.certificate(), ssc.privateKey());
          } else {
              sslCtx = null;
          }
  
          EventLoopGroup bossGroup = new NioEventLoopGroup();
          EventLoopGroup workerGroup = new NioEventLoopGroup();
          try {
              ServerBootstrap b = new ServerBootstrap();
              b.option(ChannelOption.SO_BACKLOG, 1024);
              b.group(bossGroup, workerGroup)
               .channel(NioServerSocketChannel.class)
               .handler(new LoggingHandler(LogLevel.INFO))
               .childHandler(new HttpHelloWorldServerInitializer(sslCtx));
  
              Channel ch = b.bind(PORT).sync().channel();
  
              System.err.println("Open your web browser and navigate to " +
                      (SSL? "https" : "http") + "://127.0.0.1:" + PORT + '/');
  
              ch.closeFuture().sync();
          } finally {
              bossGroup.shutdownGracefully();
              workerGroup.shutdownGracefully();
          }
      }
}

public class HttpHelloWorldServerInitializer extends ChannelInitializer<SocketChannel> {

    private final SslContext sslCtx;

    public HttpHelloWorldServerInitializer(SslContext sslCtx) {
        this.sslCtx = sslCtx;
    }

    @Override
    public void initChannel(SocketChannel ch) {
        ChannelPipeline p = ch.pipeline();
        if (sslCtx != null) {
            p.addLast(sslCtx.newHandler(ch.alloc()));
        }
        p.addLast(new HttpServerCodec());   // !使用http通信, HttpRequest和HttpResponse
        p.addLast(new HttpHelloWorldServerHandler());
    }
}

public class HttpHelloWorldServerHandler extends ChannelHandlerAdapter {
    private static final byte[] CONTENT = "HELLO WORLD".getBytes();

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        ctx.flush();
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        if (msg instanceof HttpRequest) {
            HttpRequest req = (HttpRequest) msg;

            if (HttpHeaderUtil.is100ContinueExpected(req)) {
                ctx.write(new DefaultFullHttpResponse(HTTP_1_1, CONTINUE));
            }
            boolean keepAlive = HttpHeaderUtil.isKeepAlive(req);
            // 构造响应
            FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK, Unpooled.wrappedBuffer(CONTENT));
            response.headers().set(CONTENT_TYPE, "text/plain;charset=UTF-8");
            response.headers().setInt(CONTENT_LENGTH, response.content().readableBytes());

            if (!keepAlive) {
                // Request短连接, 写完后直接关闭
                ctx.write(response).addListener(ChannelFutureListener.CLOSE);
            } else {
                // 长连接, response也设置为KEEP_ALIVE
                response.headers().set(CONNECTION, HttpHeaderValues.KEEP_ALIVE);
                ctx.write(response);
            }
        }
    }

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

3.2 HTTP下载文件

public class HttpDownloadServer {

    private static final String DEFAULT_URL = "/sources/";

    public void run(final int port, final String url) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                .channel(NioServerSocketChannel.class)
                .childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    // addLast的第一项为key, 自定义的
                    // request解码器
                    ch.pipeline().addLast("http-decoder", new HttpRequestDecoder());
                    // response的编码器
                    ch.pipeline().addLast("http-encoder", new HttpResponseEncoder());
                    // chunked, 传输文件时分多个response分解地传输文件
                    ch.pipeline().addLast("http-chunked", new ChunkedWriteHandler());
                    // ObjectAggregator, 将多个response合并为一个FullHttpResponse
                    ch.pipeline().addLast("http-aggregator", new HttpObjectAggregator(65536));
                    // 自定义业务逻辑handler
                    ch.pipeline().addLast("fileServerHandler", new HttpDownoadServerHandler(url));
                }
                });
            ChannelFuture future = b.bind("127.0.0.1", port).sync();
            System.out.println("HTTP文件目录服务器启动，网址是 : " + "http://localhost:"  + port + url);
            future.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        int port = 8765;
        new HttpDownloadServer().run(port, DEFAULT_URL);
    }
}

// 注意这里继承了SimpleChannelInboundHandler<T>, 含泛型, 即指定了传入参数msg的类型
public class HttpDownoadServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
    
    private final String url;

    public HttpDownoadServerHandler(String url) {
        this.url = url;
    }

    @Override
    public void messageReceived(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
        //是否能理解(解码)请求
        if (!request.decoderResult().isSuccess()) {
            // 400
            sendError(ctx, BAD_REQUEST);
            return;
        }
        //对请求的方法进行判断：如果不是GET方法则返回异常
        if (request.method() != GET) {
            // 405
            sendError(ctx, METHOD_NOT_ALLOWED);
            return;
        }
        //获取请求uri路径
        final String uri = request.uri();
        //对url进行分析，返回本地路径
        final String path = parseURI(uri);
        //如果 路径构造不合法，则path为null
        if (path == null) {
            //403
            sendError(ctx, FORBIDDEN);
            return;
        }
        
        // 创建file对象
        File file = new File(path);
        // 文件隐藏或不存在
        if (file.isHidden() || !file.exists()) {
            // 404 
            sendError(ctx, NOT_FOUND);
            return;
        }
        // 是文件夹
        if (file.isDirectory()) {
            if (uri.endsWith("/")) {
                //如果以正常"/"结束 说明是访问的一个文件目录：则进行展示文件列表
                sendListing(ctx, file);
            } else {
                //如果非"/"结束 则重定向，让客户端补全"/"并再次请求
                sendRedirect(ctx, uri + '/');
            }
            return;
        }
        // 如果所创建的file对象不是文件类型
        if (!file.isFile()) {
            // 403
            sendError(ctx, FORBIDDEN);
            return;
        }
        
        //随机文件读写对象
        RandomAccessFile randomAccessFile = null;
        try {
            randomAccessFile = new RandomAccessFile(file, "r");// 以只读的方式打开文件
        } catch (FileNotFoundException fnfe) {
            // 404
            sendError(ctx, NOT_FOUND);
            return;
        }
        
        //获取文件长度
        long fileLength = randomAccessFile.length();
        //建立响应对象
        HttpResponse response = new DefaultHttpResponse(HTTP_1_1, OK);
        //设置响应信息
        HttpHeaderUtil.setContentLength(response, fileLength);
        //设置Content-Type
        setContentTypeHeader(response, file);
        //设置为KeepAlive
        if (HttpHeaderUtil.isKeepAlive(request)) {
            response.headers().set(CONNECTION, HttpHeaderValues.KEEP_ALIVE);
        }
        //输出response header, HttpObjectAggregator能将其与下面输出整合合并
        ctx.write(response);
        
        //写出ChunkedFile. 创建ChunkedFile需要使用RandomAccessFile并设置分段. 这里每次传输8192个字节
        ChannelFuture sendFileFuture = ctx.write(new ChunkedFile(randomAccessFile, 0, fileLength, 8192), ctx.newProgressivePromise());
        //添加传输监听
        sendFileFuture.addListener(new ChannelProgressiveFutureListener() {
            @Override
            public void operationProgressed(ChannelProgressiveFuture future, long progress, long total) {
                if (total < 0) { 
                    System.err.println("Transfer progress: " + progress);
                } else {
                    System.err.println("Transfer progress: " + progress + " / " + total);
                }
            }
            @Override
            public void operationComplete(ChannelProgressiveFuture future) throws Exception {
                System.out.println("Transfer complete.");
            }
        });
        
        //使用Chunked, 完成时需要发送标记结束的空消息体!
        ChannelFuture lastContentFuture = ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);
        //如果当前连接请求非Keep-Alive, 最后一包消息发送完后, 服务器主动关闭连接
        if (!HttpHeaderUtil.isKeepAlive(request)) {
            lastContentFuture.addListener(ChannelFutureListener.CLOSE);
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        if (ctx.channel().isActive()) {
           // 500
            sendError(ctx, INTERNAL_SERVER_ERROR);
            ctx.close();
        }
    }

    //判断非法URI的正则
    private static final Pattern INSECURE_URI = Pattern.compile(".*[<>&"].*");
    private String parseURI(String uri) {
        try {
            //使用UTF-8字符集
            uri = URLDecoder.decode(uri, "UTF-8");
        } catch (UnsupportedEncodingException e) {
            try {
                //尝试ISO-8859-1
                uri = URLDecoder.decode(uri, "ISO-8859-1");
            } catch (UnsupportedEncodingException e1) {
                //抛出预想外异常信息
                throw new Error();
            }
        }
        // 对uri进行细粒度判断：4步验证操作
        // step 1 基础验证
        if (!uri.startsWith(url)) {
            return null;
        }
        // step 2 基础验证
        if (!uri.startsWith("/")) {
            return null;
        }
        // step 3 将文件分隔符替换为本地操作系统的文件路径分隔符
        uri = uri.replace('/', File.separatorChar);
        // step 4 验证路径合法性
        if (uri.contains(File.separator + '.') || uri.contains('.' + File.separator) || 
                uri.startsWith(".") || uri.endsWith(".") || 
                INSECURE_URI.matcher(uri).matches()) {
            return null;
        }
        //利用当前工程所在目录 + URI相对路径 构造绝对路径 
        return System.getProperty("user.dir") + File.separator + uri;
    }
    
    //用正则表达式过滤文件名
    private static final Pattern ALLOWED_FILE_NAME = Pattern.compile("[A-Za-z0-9][-_A-Za-z0-9\.]*");
    //文件列表, 拼html文件
    private static void sendListing(ChannelHandlerContext ctx, File dir) {
        // 设置响应对象
        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK);
        // 响应头
        response.headers().set(CONTENT_TYPE, "text/html; charset=UTF-8");
        // 构造文本内容
        StringBuilder ret = new StringBuilder();
        String dirPath = dir.getPath();
        ret.append("<!DOCTYPE html>
");
        ret.append("<html><head><title>");
        ret.append(dirPath);
        ret.append(" 目录：");
        ret.append("</title></head><body>
");
        ret.append("<h3>");
        ret.append(dirPath).append(" 目录：");
        ret.append("</h3>
");
        ret.append("<ul>");
        ret.append("<li>链接：<a href="../">..</a></li>
");
        
        // 遍历文件, 生成超链接
        for (File f : dir.listFiles()) {
            //step 1: 跳过隐藏文件和不可读文件 
            if (f.isHidden() || !f.canRead()) {
                continue;
            }
            String name = f.getName();
            //step 2: 跳过正则过滤的文件名
            if (!ALLOWED_FILE_NAME.matcher(name).matches()) {
                continue;
            }
            ret.append("<li>链接：<a href="");
            ret.append(name);
            ret.append("">");
            ret.append(name);
            ret.append("</a></li>
");
        }
        ret.append("</ul></body></html>
");
        //构造ByteBuf，写入缓冲区
        ByteBuf buffer = Unpooled.copiedBuffer(ret, CharsetUtil.UTF_8);
        //进行写出操作
        response.content().writeBytes(buffer);
        //重置ByteBuf
        buffer.release();
        //发送完成并主动关闭连接
        ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
    }

    //重定向操作
    private static void sendRedirect(ChannelHandlerContext ctx, String newUri) {
        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, FOUND);
        response.headers().set(LOCATION, newUri);
        ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
    }

    //错误信息
    private static void sendError(ChannelHandlerContext ctx, HttpResponseStatus status) {
        FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, status, Unpooled.copiedBuffer("Failure: " + status.toString()+ "
", CharsetUtil.UTF_8));
        response.headers().set(CONTENT_TYPE, "text/plain; charset=UTF-8");
        ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
    }

    private static void setContentTypeHeader(HttpResponse response, File file) {
        //使用mime对象获取文件对应的Content-Type
        MimetypesFileTypeMap mimeTypesMap = new MimetypesFileTypeMap();
        response.headers().set(CONTENT_TYPE, mimeTypesMap.getContentType(file.getPath()));
    }
}

3.3 HTTP上传文件 (较少使用)

实际应用中文件上传服务端有成熟的框架fastDFS(小文件)和HDFS(大文件)

如要实现断点续传, 需要记录上传进度. 参考HTTP头的Range和Content-Range

public final class HttpUploadServer {

    static final boolean SSL = System.getProperty("ssl") != null;
    static final int PORT = Integer.parseInt(System.getProperty("port", SSL? "8443" : "8080"));

    public static void main(String[] args) throws Exception {
        // Configure SSL.
        final SslContext sslCtx;
        if (SSL) {
            SelfSignedCertificate ssc = new SelfSignedCertificate();
            sslCtx = SslContext.newServerContext(ssc.certificate(), ssc.privateKey());
        } else {
            sslCtx = null;
        }

        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup);
            b.channel(NioServerSocketChannel.class);
            b.handler(new LoggingHandler(LogLevel.INFO));
            b.childHandler(new HttpUploadServerInitializer(sslCtx));

            Channel ch = b.bind(PORT).sync().channel();
            System.err.println("Open your web browser and navigate to " + (SSL ? "https" : "http") + "://127.0.0.1:" + PORT + '/');

            ch.closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

public class HttpUploadServerInitializer extends ChannelInitializer<SocketChannel> {

    private final SslContext sslCtx;

    public HttpUploadServerInitializer(SslContext sslCtx) {
        this.sslCtx = sslCtx;
    }

    @Override
    public void initChannel(SocketChannel ch) {
        ChannelPipeline pipeline = ch.pipeline();
        if (sslCtx != null) {
            pipeline.addLast(sslCtx.newHandler(ch.alloc()));
        }
        pipeline.addLast(new HttpRequestDecoder());
        pipeline.addLast(new HttpResponseEncoder());
        // 压缩
        pipeline.addLast(new HttpContentCompressor());
        pipeline.addLast(new HttpUploadServerHandler());
    }
}

public class HttpUploadServerHandler extends SimpleChannelInboundHandler<HttpObject> {

    private static final Logger logger = Logger.getLogger(HttpUploadServerHandler.class.getName());

    private HttpRequest request;

    private boolean readingChunks;

    private final StringBuilder responseContent = new StringBuilder();

    private static final HttpDataFactory factory = new DefaultHttpDataFactory(DefaultHttpDataFactory.MINSIZE); // 大小超过minsize放磁盘上

    private HttpPostRequestDecoder decoder;
    
    static {
        DiskFileUpload.deleteOnExitTemporaryFile = true; //退出时是否删除临时文件
        DiskFileUpload.baseDirectory = "D:" + File.separatorChar + "aa";  //文件存储路径
        
        DiskAttribute.deleteOnExitTemporaryFile = true; //退出时是否删除临时文件
        DiskAttribute.baseDirectory = "D:" + File.separatorChar + "aa"; //文件存储路径
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        if (decoder != null) {
            decoder.cleanFiles();
        }
    }

    @Override
    public void messageReceived(ChannelHandlerContext ctx, HttpObject msg) throws Exception {
        if (msg instanceof HttpRequest) {           // HttpRequest传输头
            HttpRequest request = this.request = (HttpRequest) msg;
            URI uri = new URI(request.uri());
            if (!uri.getPath().startsWith("/form")) {
                // 返回上传菜单
                writeMenu(ctx);
                return;
            }
            // 拼接反馈内容
            responseContent.setLength(0);
            responseContent.append("WELCOME TO THE WILD WILD WEB SERVER
");
            responseContent.append("===================================
");
            responseContent.append("VERSION: " + request.protocolVersion().text() + "
");
            responseContent.append("REQUEST_URI: " + request.uri() + "

");
            responseContent.append("

");

            for (Entry<CharSequence, CharSequence> entry : request.headers()) {
                responseContent.append("HEADER: " + entry.getKey() + '=' + entry.getValue() + "
");
            }
            responseContent.append("

");

            Set<Cookie> cookies = null;
            String value = request.headers().getAndConvert(HttpHeaderNames.COOKIE);
            if (value == null) {
                cookies = Collections.emptySet();
            } else {
                cookies = ServerCookieDecoder.decode(value);
            }
            for (Cookie cookie : cookies) {
                responseContent.append("COOKIE: " + cookie + "
");
            }
            responseContent.append("

");

            QueryStringDecoder decoderQuery = new QueryStringDecoder(request.uri());
            Map<String, List<String>> uriAttributes = decoderQuery.parameters();
            for (Entry<String, List<String>> attr: uriAttributes.entrySet()) {
                for (String attrVal: attr.getValue()) {
                    responseContent.append("URI: " + attr.getKey() + '=' + attrVal + "
");
                }
            }
            responseContent.append("

");

            // GET方法, 就此return
            if (request.method().equals(HttpMethod.GET)) {
                responseContent.append("

END OF GET CONTENT
");
                return;
            }
            
            // POST方法
            try {
                decoder = new HttpPostRequestDecoder(factory, request);
            } catch (ErrorDataDecoderException e1) {
                e1.printStackTrace();
                responseContent.append(e1.getMessage());
                writeResponse(ctx.channel());
                ctx.channel().close();
                return;
            }

            readingChunks = HttpHeaderUtil.isTransferEncodingChunked(request);
            responseContent.append("Is Chunked: " + readingChunks + "
");
            responseContent.append("IsMultipart: " + decoder.isMultipart() + "
");
            if (readingChunks) {
                responseContent.append("Chunks: ");
            }
        }

        if (decoder != null) {
            if (msg instanceof HttpContent) {    //HttpContent具体传输的内容
                // 读取到一个chunk
                HttpContent chunk = (HttpContent) msg;
                try {
                    decoder.offer(chunk);
                } catch (ErrorDataDecoderException e1) {
                    e1.printStackTrace();
                    responseContent.append(e1.getMessage());
                    writeResponse(ctx.channel());
                    ctx.channel().close();
                    return;
                }
                responseContent.append('o'); //每读一个chunk标记一个'o'
                readHttpDataChunkByChunk();
                // 最后一块chunk
                if (chunk instanceof LastHttpContent) {
                    writeResponse(ctx.channel());
                    readingChunks = false;
                    reset();
                }
            }
        } else {
            writeResponse(ctx.channel());
        }
    }

    private void reset() {
        request = null;
        decoder.destroy(); //释放资源
        decoder = null;
    }

    private void readHttpDataChunkByChunk() throws Exception {
        try {
            while (decoder.hasNext()) {
                InterfaceHttpData data = decoder.next();
                if (data != null) {
                    try {
                        writeHttpData(data);
                    } finally {
                        data.release();
                    }
                }
            }
        } catch (EndOfDataDecoderException e1) {
            responseContent.append("

END OF CONTENT CHUNK BY CHUNK

");
        }
    }

    private void writeHttpData(InterfaceHttpData data) throws Exception {
        if (data.getHttpDataType() == HttpDataType.Attribute) {
            Attribute attribute = (Attribute) data;
            String value = null;
            try {
                value = attribute.getValue();
            } catch (IOException e1) {
                e1.printStackTrace();
                responseContent.append("
BODY Attribute: " + attribute.getHttpDataType().name() + ": " + attribute.getName() + " Error while reading value: " + e1.getMessage() + "
");
                return;
            }
            if (value.length() > 100) {
                responseContent.append("
BODY Attribute: " + attribute.getHttpDataType().name() + ": " + attribute.getName() + " data too long
");
            } else {
                responseContent.append("
BODY Attribute: " + attribute.getHttpDataType().name() + ": " + attribute + "
");
            }
        } else {
            responseContent.append("
 -----------start-------------" + "
");
            responseContent.append("
BODY FileUpload: " + data.getHttpDataType().name() + ": " + data + "
");
            responseContent.append("
 ------------end------------" + "
");
            if (data.getHttpDataType() == HttpDataType.FileUpload) {
                FileUpload fileUpload = (FileUpload) data;
                if (fileUpload.isCompleted()) {
                    System.out.println("file name : " + fileUpload.getFilename());
                    System.out.println("file length: " + fileUpload.length());
                    System.out.println("file maxSize : " + fileUpload.getMaxSize());
                    System.out.println("file path :" + fileUpload.getFile().getPath());
                    System.out.println("file absolutepath :" + fileUpload.getFile().getAbsolutePath());
                    System.out.println("parent path :" + fileUpload.getFile().getParentFile());
                    
                    if (fileUpload.length() < 1024 * 1024 * 10) {
                        responseContent.append("	Content of file
");
                        try {
                            responseContent.append(fileUpload.getString(fileUpload.getCharset()));
                        } catch (Exception e1) {
                            e1.printStackTrace();
                        }
                        responseContent.append("
");
                    } else {
                        responseContent.append("	File too long to be printed out:" + fileUpload.length() + "
");
                    }
                    fileUpload.renameTo(new File(fileUpload.getFile().getPath())); // 核心操作, 写文件
                    decoder.removeHttpDataFromClean(fileUpload); 
                } else {
                    responseContent.append("	File to be continued but should not!
");
                }
            }
        }
    }

    private void writeResponse(Channel channel) {
        ByteBuf buf = copiedBuffer(responseContent.toString(), CharsetUtil.UTF_8);
        responseContent.setLength(0);

        // 是否是短连接
        boolean close = request.headers().contains(HttpHeaderNames.CONNECTION, HttpHeaderValues.CLOSE, true)
                || request.protocolVersion().equals(HttpVersion.HTTP_1_0)
                && !request.headers().contains(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE, true);

        FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, buf);
        response.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/plain; charset=UTF-8");
        // 最后一次连接不需要Content-Length
        if (!close) {
            response.headers().setInt(HttpHeaderNames.CONTENT_LENGTH, buf.readableBytes());
        }

        Set<Cookie> cookies = null;
        String value = request.headers().getAndConvert(HttpHeaderNames.COOKIE);
        if (value == null) {
            cookies = Collections.emptySet();
        } else {
            cookies = ServerCookieDecoder.decode(value);
        }
        if (!cookies.isEmpty()) {
            for (Cookie cookie : cookies) {
                response.headers().add(HttpHeaderNames.SET_COOKIE, ServerCookieEncoder.encode(cookie));
            }
        }
        ChannelFuture future = channel.writeAndFlush(response);
        if (close) {
            future.addListener(ChannelFutureListener.CLOSE);
        }
    }
    
    //拼接上传页html菜单
    private void writeMenu(ChannelHandlerContext ctx) {
        responseContent.setLength(0);

        // create Pseudo Menu
        responseContent.append("<html>");
        responseContent.append("<head>");
        responseContent.append("<title>Netty Test Form</title>
");
        responseContent.append("</head>
");
        responseContent.append("<body bgcolor=white><style>td{font-size: 12pt;}</style>");

        responseContent.append("<table border="0">");
        responseContent.append("<tr>");
        responseContent.append("<td>");
        responseContent.append("<h1>Netty Test Form</h1>");
        responseContent.append("Choose one FORM");
        responseContent.append("</td>");
        responseContent.append("</tr>");
        responseContent.append("</table>
");

        // GET
        responseContent.append("<CENTER>GET FORM<HR WIDTH="75%" NOSHADE color="blue"></CENTER>");
        responseContent.append("<FORM ACTION="/formget" METHOD="GET">");
        responseContent.append("<input type=hidden name=getform value="GET">");
        responseContent.append("<table border="0">");
        responseContent.append("<tr><td>Fill with value: <br> <input type=text name="info" size=10></td></tr>");
        responseContent.append("<tr><td>Fill with value: <br> <input type=text name="secondinfo" size=20>");
        responseContent.append("<tr><td>Fill with value: <br> <textarea name="thirdinfo" cols=40 rows=10></textarea>");
        responseContent.append("</td></tr>");
        responseContent.append("<tr><td><INPUT TYPE="submit" NAME="Send" VALUE="Send"></INPUT></td>");
        responseContent.append("<td><INPUT TYPE="reset" NAME="Clear" VALUE="Clear" ></INPUT></td></tr>");
        responseContent.append("</table></FORM>
");
        responseContent.append("<CENTER><HR WIDTH="75%" NOSHADE color="blue"></CENTER>");

        // POST
        responseContent.append("<CENTER>POST FORM<HR WIDTH="75%" NOSHADE color="blue"></CENTER>");
        responseContent.append("<FORM ACTION="/formpost" METHOD="POST">");
        responseContent.append("<input type=hidden name=getform value="POST">");
        responseContent.append("<table border="0">");
        responseContent.append("<tr><td>Fill with value: <br> <input type=text name="info" size=10></td></tr>");
        responseContent.append("<tr><td>Fill with value: <br> <input type=text name="secondinfo" size=20>");
        responseContent.append("<tr><td>Fill with value: <br> <textarea name="thirdinfo" cols=40 rows=10></textarea>");
        responseContent.append("<tr><td>Fill with file (only file name will be transmitted): <br> <input type=file name="myfile">");
        responseContent.append("</td></tr>");
        responseContent.append("<tr><td><INPUT TYPE="submit" NAME="Send" VALUE="Send"></INPUT></td>");
        responseContent.append("<td><INPUT TYPE="reset" NAME="Clear" VALUE="Clear" ></INPUT></td></tr>");
        responseContent.append("</table></FORM>
");
        responseContent.append("<CENTER><HR WIDTH="75%" NOSHADE color="blue"></CENTER>");

        // POST with enctype="multipart/form-data"
        responseContent.append("<CENTER>POST MULTIPART FORM<HR WIDTH="75%" NOSHADE color="blue"></CENTER>");
        responseContent.append("<FORM ACTION="/formpostmultipart" ENCTYPE="multipart/form-data" METHOD="POST">");
        responseContent.append("<input type=hidden name=getform value="POST">");
        responseContent.append("<table border="0">");
        responseContent.append("<tr><td>Fill with value: <br> <input type=text name="info" size=10></td></tr>");
        responseContent.append("<tr><td>Fill with value: <br> <input type=text name="secondinfo" size=20>");
        responseContent.append("<tr><td>Fill with value: <br> <textarea name="thirdinfo" cols=40 rows=10></textarea>");
        responseContent.append("<tr><td>Fill with file: <br> <input type=file name="myfile">");
        responseContent.append("</td></tr>");
        responseContent.append("<tr><td><INPUT TYPE="submit" NAME="Send" VALUE="Send"></INPUT></td>");
        responseContent.append("<td><INPUT TYPE="reset" NAME="Clear" VALUE="Clear" ></INPUT></td></tr>");
        responseContent.append("</table></FORM>
");
        responseContent.append("<CENTER><HR WIDTH="75%" NOSHADE color="blue"></CENTER>");

        responseContent.append("</body>");
        responseContent.append("</html>");

        ByteBuf buf = copiedBuffer(responseContent.toString(), CharsetUtil.UTF_8);
        FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, buf);
        response.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/html; charset=UTF-8");
        response.headers().setInt(HttpHeaderNames.CONTENT_LENGTH, buf.readableBytes());

        ctx.channel().writeAndFlush(response);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        logger.log(Level.WARNING, responseContent.toString(), cause);
        ctx.channel().close();
    }
}

3.4 WebSocket(较少使用)

public class WebSocketServer {
    public void run(int port) throws Exception {
    EventLoopGroup bossGroup = new NioEventLoopGroup();
    EventLoopGroup workerGroup = new NioEventLoopGroup();
    ServerBootstrap b = new ServerBootstrap();
    b.group(bossGroup, workerGroup)
        .channel(NioServerSocketChannel.class)
        .childHandler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel ch) throws Exception {
                ChannelPipeline pipeline = ch.pipeline();
                pipeline.addLast("http-codec", new HttpServerCodec());
                pipeline.addLast("aggregator", new HttpObjectAggregator(65536));
                ch.pipeline().addLast("http-chunked", new ChunkedWriteHandler());
                pipeline.addLast("handler", new WebSocketServerHandler());
            }
     });

    Channel ch = b.bind(port).sync().channel();
    System.out.println("Web socket server started at port " + port + '.');
    System.out.println("Open your browser and navigate to http://localhost:" + port + '/');

    ch.closeFuture().sync();
    bossGroup.shutdownGracefully();
    workerGroup.shutdownGracefully();
    }

    public static void main(String[] args) throws Exception {
        new WebSocketServer().run(8765);
    }
}

public class WebSocketServerHandler extends SimpleChannelInboundHandler<Object> {
    private static final Logger logger = Logger.getLogger(WebSocketServerHandler.class.getName());

    private WebSocketServerHandshaker handshaker;

    @Override
    public void messageReceived(ChannelHandlerContext ctx, Object msg) throws Exception {
        // 传统的HTTP接入
        if (msg instanceof FullHttpRequest) {
            handleHttpRequest(ctx, (FullHttpRequest) msg);
        }
        // WebSocket接入
        else if (msg instanceof WebSocketFrame) {
            handleWebSocketFrame(ctx, (WebSocketFrame) msg);
        }
    }

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

    private void handleHttpRequest(ChannelHandlerContext ctx, FullHttpRequest req) throws Exception {
        // 如果HTTP解码失败，返回HTTP异常
        if (!req.decoderResult().isSuccess() || (!"websocket".equals(req.headers().get("Upgrade")))) {
            sendHttpResponse(ctx, req, new DefaultFullHttpResponse(HTTP_1_1, BAD_REQUEST));
            return;
        }
    
        // 构造握手响应返回，本机测试
        WebSocketServerHandshakerFactory wsFactory = new WebSocketServerHandshakerFactory("ws://localhost:8080/websocket", null, false);
        handshaker = wsFactory.newHandshaker(req);
        
        if (handshaker == null) {
            WebSocketServerHandshakerFactory.sendUnsupportedVersionResponse(ctx.channel());
        } else {
            handshaker.handshake(ctx.channel(), req);
        }
    }

    private void handleWebSocketFrame(ChannelHandlerContext ctx, WebSocketFrame frame) {

        // 判断是否是关闭链路的指令
        if (frame instanceof CloseWebSocketFrame) {
            handshaker.close(ctx.channel(), (CloseWebSocketFrame) frame.retain());
            return;
        }
        // 判断是否是Ping消息
        if (frame instanceof PingWebSocketFrame) {
            ctx.channel().write(new PongWebSocketFrame(frame.content().retain()));
            return;
        }
        // 本例程仅支持文本消息，不支持二进制消息
        if (!(frame instanceof TextWebSocketFrame)) {
            throw new UnsupportedOperationException(String.format("%s frame types not supported", frame.getClass().getName()));
        }
    
        // 返回应答消息
        String request = ((TextWebSocketFrame) frame).text();
        if (logger.isLoggable(Level.FINE)) {
            logger.fine(String.format("%s received %s", ctx.channel(), request));
        }
        ctx.channel().write(
            new TextWebSocketFrame(request + " , 欢迎使用Netty WebSocket服务，现在时刻：" + new java.util.Date().toString()));
    }

    private static void sendHttpResponse(ChannelHandlerContext ctx, FullHttpRequest req, FullHttpResponse res) {
        // 返回应答给客户端
        if (res.status().code() != 200) {
            ByteBuf buf = Unpooled.copiedBuffer(res.status().toString(), CharsetUtil.UTF_8);
            res.content().writeBytes(buf);
            buf.release();
            HttpHeaderUtil.setContentLength(res, res.content().readableBytes());
        }
    
        // 如果是非Keep-Alive，关闭连接
        ChannelFuture f = ctx.channel().writeAndFlush(res);
        if (!HttpHeaderUtil.isKeepAlive(req) || res.status().code() != 200) {
            f.addListener(ChannelFutureListener.CLOSE);
        }
    }

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

客户端是网页

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
Netty WebSocket 时间服务器
</head>
<br>
<body>
    <br>
    <script type="text/javascript">
        var socket;
        if (!window.WebSocket) {
            window.WebSocket = window.MozWebSocket;
        }
        if (window.WebSocket) {
            socket = new WebSocket("ws://localhost:8765/websocket");
            socket.onmessage = function(event) {
                var ta = document.getElementById('responseText');
                ta.value = "";
                ta.value = event.data
            };
            socket.onopen = function(event) {
                var ta = document.getElementById('responseText');
                ta.value = "打开WebSocket服务正常，浏览器支持WebSocket!";
            };
            socket.onclose = function(event) {
                var ta = document.getElementById('responseText');
                ta.value = "";
                ta.value = "WebSocket 关闭!";
            };
        } else {
            alert("抱歉，您的浏览器不支持WebSocket协议!");
        }

        function send(message) {
            if (!window.WebSocket) {
                return;
            }
            if (socket.readyState == WebSocket.OPEN) {
                socket.send(message);
            } else {
                alert("WebSocket连接没有建立成功!");
            }
        }
    </script>
    <form onsubmit="return false;">
        <input type="text" name="message" value="Netty最佳实践" /> <br>
        <br> <input type="button" value="发送WebSocket请求消息"
            onclick="send(this.form.message.value)" />
        <hr color="blue" />
        <h3>服务端返回的应答消息</h3>
        <textarea id="responseText" style=" 500px; height: 300px;"></textarea>
    </form>
</body>
</html>