【Echo服务端】

【EchoServer】

public class EchoServer { private final int port; public EchoServer(int port) { this.port = port; } public static void main(String[] args) throws Exception { new EchoServer(9999).start(); } public void start() throws Exception { NioEventLoopGroup group = new NioEventLoopGroup(); try { ServerBootstrap b = new ServerBootstrap(); //创建ServerBootstrap b.group(group) .channel(NioServerSocketChannel.class) //指定NIO的传输Channel .localAddress(new InetSocketAddress(port)) .childHandler(new ChannelInitializer<SocketChannel>() { @Override protected void initChannel(SocketChannel channel) throws Exception { channel.pipeline().addLast(new EchoServerHandler()); //添加EchoServerHandler到Channel的ChannelPipeline } }); ChannelFuture future = b.bind().sync(); //绑定服务器，sync等待服务器关闭 System.out.println(EchoServer.class.getName() + " started and listen on " + future.channel().localAddress()); future.channel().closeFuture().sync(); } finally { group.shutdownGracefully().sync(); } }}

【EchoServerHandler】

public class EchoServerHandler extends ChannelInboundHandlerAdapter { @Override public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { ByteBuf in = (ByteBuf)msg; System.out.println("Server received:"+in.toString(CharsetUtil.UTF_8)); ctx.write(in); } @Override public void channelReadComplete(ChannelHandlerContext ctx) throws Exception { ctx.writeAndFlush(Unpooled.EMPTY_BUFFER) .addListener(ChannelFutureListener.CLOSE); } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { cause.printStackTrace(); ctx.close(); } @Override public void channelActive(ChannelHandlerContext ctx) throws Exception { System.out.println("Server is Active......"); }}

[ 说明 ] 

Echo的Handler实现了服务器的业务，决定了连接创建以后和收到信息后该如何处理。

ChannelInboundHandler的实现方法作用channelRead() //每次收到信息都会回调channelReadComplete() //channelRead执行结束时回调exceptionCaught() //执行异常情况下会被回调。

【Echo客户端】

【EchoClient】

public class EchoClient { private final String host; private final int port; public EchoClient(String host, int port) { this.host = host; this.port = port; } public static void main(String[] args) throws Exception{ new EchoClient("127.0.0.1",9999).start(); } public void start() throws Exception{ EventLoopGroup group = new NioEventLoopGroup(); try{ Bootstrap b = new Bootstrap(); b.group(group) .channel(NioSocketChannel.class) .remoteAddress(new InetSocketAddress(host,port)) .handler(new ChannelInitializer<SocketChannel>() { @Override protected void initChannel(SocketChannel channel) throws Exception { channel.pipeline().addLast( new EchoClientHandler() ); } }); ChannelFuture future = b.connect().sync(); future.channel().closeFuture().sync(); }finally { group.shutdownGracefully(); } }}

【EchoClientHandler】

public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> { @Override public void channelActive(ChannelHandlerContext ctx) throws Exception { System.out.println("client is active......"); ctx.writeAndFlush(Unpooled.copiedBuffer("Netty rocks!", CharsetUtil.UTF_8)); } @Override protected void channelRead0(ChannelHandlerContext channelHandlerContext, ByteBuf in) throws Exception { System.out.println("client received:"+ in.toString(CharsetUtil.UTF_8)); } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { cause.printStackTrace(); ctx.close(); }}

【运行结果】

[ 服务端 ]

[ 客户端 ]