粘包示例

服务端

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

import java.nio.charset.Charset;

public class ServerHandler extends SimpleChannelInboundHandler<ByteBuf> {

    private int count; // 计数器

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
        // 接收消息
        byte[] bytes = new byte[msg.readableBytes()];
        msg.readBytes(bytes);
        System.out.println("服务端收到: " + new String(bytes, Charset.forName("UTF-8")));
        System.out.println("计数：" + (++count));

        // 发送消息
        ctx.writeAndFlush(Unpooled.copiedBuffer("abc", Charset.forName("UTF-8")));
    }
}

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;

public class Server {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup parentGroup = new NioEventLoopGroup(1);
        EventLoopGroup childGroup = new NioEventLoopGroup();

        try {
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap.group(parentGroup, childGroup).channel(NioServerSocketChannel.class)
                    .handler(new LoggingHandler(LogLevel.INFO))
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new ServerHandler());
                        }
                    });
            ChannelFuture channelFuture = bootstrap.bind(8899).sync();
            channelFuture.channel().closeFuture().sync();
        } finally {
            parentGroup.shutdownGracefully();
            childGroup.shutdownGracefully();
        }
    }
}

客户端

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

import java.nio.charset.Charset;

public class ClientHandler extends SimpleChannelInboundHandler<ByteBuf> {

    private int count; // 计数器

    // 发送消息
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        for (int i = 0; i < 10; i++) {
            ctx.writeAndFlush(Unpooled.copiedBuffer("ABC", Charset.forName("UTF-8")));
        }
    }

    // 接收消息
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
        byte[] bytes = new byte[msg.readableBytes()];
        msg.readBytes(bytes);
        System.out.println("客户端收到: " + new String(bytes, Charset.forName("UTF-8")));
        System.out.println("计数：" + (++count));
    }
}

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;

public class Client {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(eventLoopGroup).channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new ClientHandler());
                        }
                    });

            ChannelFuture channelFuture = bootstrap.connect("localhost", 8899).sync();
            channelFuture.channel().closeFuture().sync();
        } finally {
            eventLoopGroup.shutdownGracefully();
        }
    }
}

自定义协议处理粘包问题

/**
 * Netty所谓的自定义协议，其实就是规定好输入输出的格式
 */
public class Protocol {

    private int length;
    private byte[] content;

    public int getLength() {
        return length;
    }

    public void setLength(int length) {
        this.length = length;
    }

    public byte[] getContent() {
        return content;
    }

    public void setContent(byte[] content) {
        this.content = content;
    }
}

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

import java.nio.charset.Charset;

public class ClientHandler extends SimpleChannelInboundHandler<Protocol> {

    private int count; // 计数器

    // 发送消息
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        for (int i = 0; i < 10; i++) {
            // 每次发送的消息都是按照自定义协议的格式
            Protocol protocol = new Protocol();
            protocol.setLength("ABC".getBytes().length);
            protocol.setContent("ABC".getBytes());
            ctx.writeAndFlush(protocol);
        }
    }

    // 接收消息
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, Protocol msg) throws Exception {
        System.out.println("客户端收到: length - " + msg.getLength() + ", content - " + new String(msg.getContent(), Charset.forName("UTF-8")));
        System.out.println("计数：" + (++count));
    }


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

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;

/**
 * 出站编码器
 */
public class Encoder extends MessageToByteEncoder<Protocol> {
    @Override
    protected void encode(ChannelHandlerContext ctx, Protocol msg, ByteBuf out) throws Exception {
        // 每次写出站的都是一个自定义Protocol
        // 按照一个Length,一个Content的格式出站
        out.writeInt(msg.getLength());
        out.writeBytes(msg.getContent());
    }
}

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ReplayingDecoder;

import java.util.List;

/**
 * 入站解码器
 */
public class Decoder extends ReplayingDecoder<Void> {
    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        /*从出站解码器接收数据，出站时数据格式是：
            一个Length表示接下来数据的长度，
            一个Content是接下来的数据
            +--------+----------------+
            | Length | Actual Content |
            | 0x000E | "HELLO, WORLD" |
            +--------+----------------+
         */
        // 接收数据,解码
        int length = in.readInt();
        byte[] content = new byte[length];
        in.readBytes(content);

        // 封装成自定义协议的格式，转发给下一个Handler
        Protocol protocol = new Protocol();
        protocol.setLength(length);
        protocol.setContent(content);
        out.add(protocol);
    }
}

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

import java.nio.charset.Charset;

public class ServerHandler extends SimpleChannelInboundHandler<Protocol> {

    private int count; // 计数器

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, Protocol msg) throws Exception {
        // 接收消息
        System.out.println("服务端收到: length - " + msg.getLength() + ", content - " + new String(msg.getContent(), Charset.forName("UTF-8")));
        System.out.println("计数：" + (++count));

        // 发送消息
        Protocol protocol = new Protocol();
        protocol.setLength("abc".getBytes().length);
        protocol.setContent("abc".getBytes());
        ctx.writeAndFlush(protocol);
    }

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

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;

public class Server {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup parentGroup = new NioEventLoopGroup(1);
        EventLoopGroup childGroup = new NioEventLoopGroup();

        try {
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap.group(parentGroup, childGroup).channel(NioServerSocketChannel.class)
                    .handler(new LoggingHandler(LogLevel.INFO))
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new Decoder());
                            pipeline.addLast(new Encoder());
                            pipeline.addLast(new ServerHandler());
                        }
                    });
            ChannelFuture channelFuture = bootstrap.bind(8899).sync();
            channelFuture.channel().closeFuture().sync();
        } finally {
            parentGroup.shutdownGracefully();
            childGroup.shutdownGracefully();
        }
    }
}

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;

public class Client {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(eventLoopGroup).channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new Decoder());
                            pipeline.addLast(new Encoder());
                            pipeline.addLast(new ClientHandler());
                        }
                    });

            ChannelFuture channelFuture = bootstrap.connect("localhost", 8899).sync();
            channelFuture.channel().closeFuture().sync();
        } finally {
            eventLoopGroup.shutdownGracefully();
        }
    }
}