https://github.com/netty/netty/tree/4.1/example/
Server端 import io.netty.bootstrap.ServerBootstrap; import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import io.netty.channel.*; import io.netty.channel.nio.NioEventLoopGroup; import io.netty.channel.socket.SocketChannel; import io.netty.channel.socket.nio.NioServerSocketChannel; import io.netty.util.CharsetUtil; public class NettyServer { public static void main(String[] args) throws Exception { EventLoopGroup bossGroup = new NioEventLoopGroup(1); EventLoopGroup workerGroup = new NioEventLoopGroup(); try { ServerBootstrap bootstrap = new ServerBootstrap() .group(bossGroup, workerGroup) .channel(NioServerSocketChannel.class) .option(ChannelOption.SO_BACKLOG, 1024) .childHandler(new ChannelInitializer<SocketChannel>() { @Override protected void initChannel(SocketChannel ch) { ch.pipeline().addLast(new NettyServerHandler()); } }); ChannelFuture cf = bootstrap.bind(8080).sync(); cf.channel().closeFuture().sync(); } finally { bossGroup.shutdownGracefully(); workerGroup.shutdownGracefully(); } } static class NettyServerHandler extends ChannelInboundHandlerAdapter { @Override public void channelRead(ChannelHandlerContext ctx, Object msg) { String message = String.format("recv client[%s] data：%s", ctx.channel().remoteAddress(), ((ByteBuf) msg).toString(CharsetUtil.UTF_8)); System.out.println(message); } @Override public void channelReadComplete(ChannelHandlerContext ctx) { ByteBuf buf = Unpooled.copiedBuffer("Hello, NettyClient!".getBytes(CharsetUtil.UTF_8)); ctx.writeAndFlush(buf); } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { cause.printStackTrace(); ctx.close(); } } } Client端 import io.netty.bootstrap.Bootstrap; import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import io.netty.channel.*; import io.netty.channel.nio.NioEventLoopGroup; import io.netty.channel.socket.SocketChannel; import io.netty.channel.socket.nio.NioSocketChannel; import io.netty.util.CharsetUtil; public class NettyClient { public static void main(String[] args) throws Exception { EventLoopGroup group = new NioEventLoopGroup(1); try { Bootstrap bootstrap = new Bootstrap() .group(group) .channel(NioSocketChannel.class) .handler(new ChannelInitializer<SocketChannel>() { @Override protected void initChannel(SocketChannel ch) { ch.pipeline().addLast(new NettyClientHandler()); } }); ChannelFuture cf = bootstrap.connect("127.0.0.1", 8080).sync(); cf.channel().closeFuture().sync(); } finally { group.shutdownGracefully(); } } static class NettyClientHandler extends ChannelInboundHandlerAdapter { @Override public void channelActive(ChannelHandlerContext ctx) { ByteBuf buf = Unpooled.copiedBuffer("Hello, NettyServer!".getBytes(CharsetUtil.UTF_8)); ctx.writeAndFlush(buf); } @Override public void channelRead(ChannelHandlerContext ctx, Object msg) { String message = String.format("recv server[%s] data：%s", ctx.channel().remoteAddress(), ((ByteBuf) msg).toString(CharsetUtil.UTF_8)); System.out.println(message); } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { cause.printStackTrace(); ctx.close(); } } } 源码追踪建议跟着我画的源码走向图，跟下面的内容，最好也开着debug模式，不理解的地方调试几遍。这里再次贴一下链接：
https://www.yuque.com/docs/share/02fa3e3d-d485-48e1-9cfe-6722a3ad8915