netty 的几个操作示例

原生的 socket 编程：Java 中的 IO 与 socket 编程 [ 复习 ]

 

介绍

Netty 项目是一个提供异步事件驱动网络应用框架。

 

示例

1.discord 服务

handler

public class DiscardServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        //默默的丢弃接收到的数据
        ByteBuf in = (ByteBuf) msg;
        try{
            System.out.println(in.toString(io.netty.util.CharsetUtil.US_ASCII));
        } finally{
            ReferenceCountUtil.release(msg); //(2)
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        //出现异常时直接关闭链接
        ctx.close();
    }
}

 server

public class DiscardServer {

    private int port;
    public DiscardServer(int port){
        this.port=port;
    }

    public void run() {
            NioEventLoopGroup bossGroup = new NioEventLoopGroup();
            NioEventLoopGroup 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 {
                            ch.pipeline().addLast(new DiscardServerHandler());
                        }
                    })
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true);
            ChannelFuture f = b.bind(port).sync();
            f.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) {
        int port;
        if(args.length>0){
            port=Integer.parseInt(args[0]);
        }else{
            port=8080;
        }
        new DiscardServer(port).run();
    }
}

 

使用命令行作为客户端

$ ncat localhost 8080
hello
hi
hello world

 

 

2.echo 服务

handler

public class EchoServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ctx.write(msg);
        ctx.flush();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        //出现异常时直接关闭链接
        ctx.close();
    }
}

 

同样命令行作为客户端

 

 

3.time 服务

server handler

public class TimeServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        final ByteBuf time = ctx.alloc().buffer(4);
        time.writeInt((int) (System.currentTimeMillis() / 1000L + 2208988800L));
        ChannelFuture f = ctx.writeAndFlush(time);
//        f.addListener(ChannelFutureListener.CLOSE);
        f.addListener(new ChannelFutureListener() {
            @Override
            public void operationComplete(ChannelFuture future) throws Exception {
                assert f == future;
                ctx.close();
            }
        });
    }

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

 

server

public class TimeServer {

    private final int port;
    public TimeServer(int port){
        this.port=port;
    }

    public void run() {
            NioEventLoopGroup bossGroup = new NioEventLoopGroup();
            NioEventLoopGroup 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 {
                            ch.pipeline().addLast(new TimeServerHandler());
                        }
                    })
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true);
            ChannelFuture f = b.bind(port).sync();
            f.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) {
        int port;
        if(args.length>0){
            port=Integer.parseInt(args[0]);
        }else{
            port=8080;
        }
        new TimeServer(port).run();
    }
}

 

client handler

public class TimeClientHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf m = (ByteBuf) msg; // (1)
        try {
            long currentTimeMillis = (m.readUnsignedInt() - 2208988800L) * 1000L;
            System.out.println(new Date(currentTimeMillis));
            ctx.close();
        } finally {
            m.release();
        }
    }

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

 

decoder

public class TimeDecoder extends ByteToMessageDecoder { // (1)
    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) { // (2)
        if (in.readableBytes() < 4) {
            return; // (3)
        }
        out.add(in.readBytes(4)); // (4)
    }
}

 

client

public class TimeClient {

    public static void main(String[] args) {
        String host = "localhost";
        int port = 8080;
        NioEventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(workerGroup);
            b.channel(NioSocketChannel.class);
            b.option(ChannelOption.SO_KEEPALIVE, true);
            b.handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new TimeDecoder(), new TimeClientHandler());
                }
            });
            //启动客户端
            ChannelFuture future = b.connect(host, port).sync();
            //在连接关闭之前保持等待
            future.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            workerGroup.shutdownGracefully();
        }
    }
}

 

4.http 服务

sever handler

public class HttpServerHandler extends SimpleChannelInboundHandler<HttpObject> {

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) throws Exception {
        Thread.sleep(3000);
        ByteBuf content = Unpooled.copiedBuffer("Hello world", CharsetUtil.UTF_8);
        DefaultFullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, content);
        response.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/plain");
        response.headers().set(HttpHeaderNames.CONTENT_LENGTH, content.readableBytes());
        ctx.writeAndFlush(response);
    }

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

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

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

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

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

 

server

public class HttpServer {

    public static void main(String[] args) {
        NioEventLoopGroup bossGroup = new NioEventLoopGroup();
        NioEventLoopGroup 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 {
                            ch.pipeline().addLast(new HttpServerCodec());
                            ch.pipeline().addLast(new HttpServerHandler());
                        }
                    });
            ChannelFuture future = b.bind(8989).sync();
            future.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

 

client

使用浏览器访问 http://localhost:8989

 

5.chat 服务

server handler

public class ChatServerHandler extends SimpleChannelInboundHandler<String> {

    private static final ChannelGroup channels = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        Channel channel = ctx.channel();
        channels.forEach(c -> {
            if (c.id() != channel.id()) {
                c.writeAndFlush(channel.remoteAddress() + ", 发送的消息：" + msg + "\n");
            } else {
                c.writeAndFlush("[自己] " + msg + "\n");
            }
        });
    }

    @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("[服务器] -" + ctx.channel().remoteAddress() + " 上线\n");
        super.channelActive(ctx);
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("[服务器] -" + ctx.channel().remoteAddress() + " 下线\n");
        super.channelInactive(ctx);
    }

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        channels.writeAndFlush("[服务器] -" + ctx.channel().remoteAddress() + " 加入\n");
        channels.add(ctx.channel());
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        channels.writeAndFlush("[服务器] -" + ctx.channel().remoteAddress() + " 离开\n");
//        channels.remove(ctx.channel());
        System.out.println("离开后，" +channels.size());
    }
}

 

server

public class ChatServer {

    public static void main(String[] args) throws InterruptedException {
        NioEventLoopGroup bossGroup = new NioEventLoopGroup();
        NioEventLoopGroup 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 {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new DelimiterBasedFrameDecoder(4096, Delimiters.lineDelimiter()));
                            pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
                            pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
                            pipeline.addLast(new ChatServerHandler());
                        }
                    });
            ChannelFuture future = b.bind(8989).sync();
            future.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

 

client handler

public class ChatClientHandler extends SimpleChannelInboundHandler<String> {

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println(msg);
    }
}

 

client

public class ChatClient {

    public static void main(String[] args) throws InterruptedException, IOException {
        NioEventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(workerGroup)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new DelimiterBasedFrameDecoder(4096, Delimiters.lineDelimiter()));
                            pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
                            pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
                            pipeline.addLast(new ChatClientHandler());
                        }
                    });
            ChannelFuture future = b.connect("localhost", 8989).sync();
            Channel channel = future.channel();
            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
            for (;;) {
                channel.writeAndFlush(reader.readLine() + "\r\n");
            }
        } finally {
            workerGroup.shutdownGracefully();
        }
    }
}

 

6.heartbeat 服务

server handler

public class HeartBeatServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        if (evt instanceof IdleStateEvent) {
            IdleStateEvent event = (IdleStateEvent) evt;
            String eventType = "";
            switch (event.state()) {
                case READER_IDLE:
                    eventType = "读空闲";
                    break;
                case WRITER_IDLE:
                    eventType = "写空闲";
                    break;
                case ALL_IDLE:
                    eventType = "读写空闲";
                    break;
            }
            System.out.println(ctx.channel().remoteAddress() + " 超时事件: " + eventType);
            ctx.channel().close();
        }
    }
}

 

server

public class HeartBeatServer {
    public static void main(String[] args) throws InterruptedException {
        NioEventLoopGroup bossGroup = new NioEventLoopGroup();
        NioEventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .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 IdleStateHandler(5,7,10));
                            pipeline.addLast(new HeartBeatServerHandler());
                        }
                    });
            ChannelFuture future = b.bind(8088).sync();
            future.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

 

客户端使用命令行

7秒内不断输入字符，服务端会打印“写空闲”

 写空闲

 

7.websocket 服务

 server handler

public class TextWsFrameHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception {
        System.out.println("收到消息: " + msg.text());
        ctx.channel().writeAndFlush(new TextWebSocketFrame("服务器时间: " + LocalDateTime.now()));
    }

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        System.out.println("handlerAdded: " + ctx.channel().id().asLongText());
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        System.out.println("handlerRemoved" + ctx.channel().id().asLongText());
    }

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

 

server

public class WsServer {

    public static void main(String[] args) throws InterruptedException {
        NioEventLoopGroup bossGroup = new NioEventLoopGroup();
        NioEventLoopGroup 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 {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new HttpServerCodec());
                            pipeline.addLast(new ChunkedWriteHandler());
                            pipeline.addLast(new HttpObjectAggregator(8192));
                            pipeline.addLast(new WebSocketServerProtocolHandler("/ws"));
                            pipeline.addLast(new TextWsFrameHandler());
                        }
                    });
            ChannelFuture fu = b.bind(8181).sync();
            fu.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

}

 

client 使用 html+js

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
</head>
<body>
  <textarea id="reply" cols="30" rows="10" placeholder="回复信息" readonly></textarea>
  <button onclick="sendMsg()">发送</button>
<script>
let socket = new WebSocket("ws://localhost:8181/ws");

function sendMsg() {
  socket.send("My name is John");
}

socket.onopen = function(e) {
  alert("[open] Connection established");
  alert("Sending to server");
};

socket.onmessage = function(event) {
  document.getElementById('reply').innerText = event.data;
};

socket.onclose = function(event) {
  if (event.wasClean) {
    alert(`[close] Connection closed cleanly, code=${event.code} reason=${event.reason}`);
  } else {
    // 例如服务器进程被杀死或网络中断
    // 在这种情况下，event.code 通常为 1006
    alert('[close] Connection died');
  }
};

socket.onerror = function(error) {
  alert(`[error] ${error.message}`);
};
</script>
</body>
</html>

 

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