read netty document chapter 1

src/main/java/com/corundumstudio/socketio/demo/discard/DiscardServer.java

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+package com.corundumstudio.socketio.demo.discard;
+
+import io.netty.bootstrap.ServerBootstrap;
+
+import io.netty.channel.ChannelFuture;
+import io.netty.channel.ChannelInitializer;
+import io.netty.channel.ChannelOption;
+import io.netty.channel.EventLoopGroup;
+import io.netty.channel.nio.NioEventLoopGroup;
+import io.netty.channel.socket.SocketChannel;
+import io.netty.channel.socket.nio.NioServerSocketChannel;
+
+/**
+ * TODO :
+ *
+ * @author ye.jf
+ * @version 0.1.0
+ * @date 2022/1/1 14:18
+ * @copyright Wonhigh Information Technology (Shenzhen) Co.,Ltd.
+ */
+public class DiscardServer {
+    private int port;
+
+    public DiscardServer(int port) {
+        this.port = port;
+    }
+
+    public void run() throws Exception {
+        EventLoopGroup bossGroup = new NioEventLoopGroup(); // (1)
+        EventLoopGroup workerGroup = new NioEventLoopGroup();
+        try {
+            ServerBootstrap b = new ServerBootstrap(); // (2)
+            b.group(bossGroup, workerGroup)
+                    .channel(NioServerSocketChannel.class) // (3)
+                    .childHandler(new ChannelInitializer<SocketChannel>() { // (4)
+                        @Override
+                        public void initChannel(SocketChannel ch) throws Exception {
+                            ch.pipeline().addLast(new DiscardServerHandler());
+                        }
+                    })
+                    .option(ChannelOption.SO_BACKLOG, 128)          // (5)
+                    .childOption(ChannelOption.SO_KEEPALIVE, true); // (6)
+
+            // Bind and start to accept incoming connections.
+            ChannelFuture f = b.bind(port).sync(); // (7)
+
+            // Wait until the server socket is closed.
+            // In this example, this does not happen, but you can do that to gracefully
+            // shut down your server.
+            f.channel().closeFuture().sync();
+        } finally {
+            workerGroup.shutdownGracefully();
+            bossGroup.shutdownGracefully();
+        }
+    }
+
+    public static void main(String[] args) throws Exception {
+        int port = 8080;
+        if (args.length > 0) {
+            port = Integer.parseInt(args[0]);
+        }
+
+        new DiscardServer(port).run();
+    }
+}

src/main/java/com/corundumstudio/socketio/demo/discard/DiscardServerHandler.java

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+package com.corundumstudio.socketio.demo.discard;
+
+import io.netty.buffer.ByteBuf;
+
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelInboundHandlerAdapter;
+import io.netty.util.ReferenceCountUtil;
+
+/**
+ * TODO :
+ *
+ * @author ye.jf
+ * @version 0.1.0
+ * @date 2022/1/1 12:33
+ * @copyright Wonhigh Information Technology (Shenzhen) Co.,Ltd.
+ */
+public class DiscardServerHandler extends ChannelInboundHandlerAdapter {
+    @Override
+    public void channelRead(ChannelHandlerContext ctx, Object msg) { // (2)
+        // Discard the received data silently.
+        System.out.println("DiscardServerHandler channelRead");
+        /*ByteBuf in = (ByteBuf) msg;
+        try {
+            // 丢弃协议实现
+            while (in.isReadable()) { // (1)
+                System.out.print((char) in.readByte());
+                System.out.flush();
+            }
+        } finally {
+            ReferenceCountUtil.release(msg);
+        }*/
+        // 响应服务实现
+        ctx.write(msg); // (1)
+        ctx.flush(); // (2)
+
+        //ctx.writeAndFlush(msg);
+
+    }
+
+    @Override
+    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { // (4)
+        // Close the connection when an exception is raised.
+        cause.printStackTrace();
+        ctx.close();
+    }
+}

src/main/java/com/corundumstudio/socketio/demo/time/TimeClient.java

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+package com.corundumstudio.socketio.demo.time;
+
+import io.netty.bootstrap.Bootstrap;
+import io.netty.channel.ChannelFuture;
+import io.netty.channel.ChannelInitializer;
+import io.netty.channel.ChannelOption;
+import io.netty.channel.EventLoopGroup;
+import io.netty.channel.nio.NioEventLoopGroup;
+import io.netty.channel.socket.SocketChannel;
+import io.netty.channel.socket.nio.NioSocketChannel;
+
+/**
+ * TODO :
+ *
+ * @author ye.jf
+ * @version 0.1.0
+ * @date 2022/1/3 13:54
+ * @copyright Wonhigh Information Technology (Shenzhen) Co.,Ltd.
+ */
+public class TimeClient {
+    public static void main(String[] args) throws Exception {
+        //String host = args[0];
+        //int port = Integer.parseInt(args[1]);
+        String host = "localhost";
+        int port = 8080;
+        EventLoopGroup workerGroup = new NioEventLoopGroup();
+
+        try {
+            Bootstrap b = new Bootstrap(); // (1)
+            b.group(workerGroup); // (2)
+            b.channel(NioSocketChannel.class); // (3)
+            b.option(ChannelOption.SO_KEEPALIVE, true); // (4)
+            b.handler(new ChannelInitializer<SocketChannel>() {
+                @Override
+                public void initChannel(SocketChannel ch) throws Exception {
+                    ch.pipeline().addLast(new TimeClientHandler());
+                }
+            });
+
+            // Start the client.
+            ChannelFuture f = b.connect(host, port).sync(); // (5)
+
+            // Wait until the connection is closed.
+            f.channel().closeFuture().sync();
+        } finally {
+            workerGroup.shutdownGracefully();
+        }
+    }
+}

src/main/java/com/corundumstudio/socketio/demo/time/TimeClientHandler.java

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+package com.corundumstudio.socketio.demo.time;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelInboundHandlerAdapter;
+
+import java.util.Date;
+
+/**
+ * TODO :
+ *
+ * @author ye.jf
+ * @version 0.1.0
+ * @date 2022/1/3 14:04
+ * @copyright Wonhigh Information Technology (Shenzhen) Co.,Ltd.
+ */
+public class TimeClientHandler extends ChannelInboundHandlerAdapter {
+    /**
+     * 以下这种实现方案有可能出现越界异常,并且在处理大数据量时,会出现数据碎片化 例如 发送方三个数据包 abc def ghi, 接收时变成 ab cdefg h i
+     *
+     * 简单的解决方案是创建一个内部累积缓冲区，并等待直到所有4个字节都被接收到内部缓冲区。
+     * @param ctx
+     * @param msg
+     */
+    /*@Override
+    public void channelRead(ChannelHandlerContext ctx, Object msg) {
+        ByteBuf m = (ByteBuf) msg; // (1)
+        try {
+            long currentTimeMillis = (m.readUnsignedInt() - 2208988800L) * 1000L;
+            System.out.println(new Date(currentTimeMillis));
+            ctx.close();
+        } finally {
+            m.release();
+        }
+    }*/
+
+    private ByteBuf buf;
+
+    @Override
+    public void handlerAdded(ChannelHandlerContext ctx) {
+        buf = ctx.alloc().buffer(4); // (1)
+    }
+
+    @Override
+    public void handlerRemoved(ChannelHandlerContext ctx) {
+        buf.release(); // (1)
+        buf = null;
+    }
+
+    @Override
+    public void channelRead(ChannelHandlerContext ctx, Object msg) {
+        ByteBuf m = (ByteBuf) msg;
+        buf.writeBytes(m); // (2)
+        m.release();
+
+        if (buf.readableBytes() >= 4) { // (3)
+            long currentTimeMillis = (buf.readUnsignedInt() - 2208988800L) * 1000L;
+            System.out.println(new Date(currentTimeMillis));
+            ctx.close();
+        }
+    }
+
+    @Override
+    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
+        cause.printStackTrace();
+        ctx.close();
+    }
+}

src/main/java/com/corundumstudio/socketio/demo/time/TimeServer.java

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+package com.corundumstudio.socketio.demo.time;
+
+import com.corundumstudio.socketio.demo.discard.DiscardServerHandler;
+import io.netty.bootstrap.ServerBootstrap;
+import io.netty.channel.ChannelFuture;
+import io.netty.channel.ChannelInitializer;
+import io.netty.channel.ChannelOption;
+import io.netty.channel.EventLoopGroup;
+import io.netty.channel.nio.NioEventLoopGroup;
+import io.netty.channel.socket.SocketChannel;
+import io.netty.channel.socket.nio.NioServerSocketChannel;
+
+/**
+ * TODO :
+ *
+ * @author ye.jf
+ * @version 0.1.0
+ * @date 2022/1/1 14:18
+ * @copyright Wonhigh Information Technology (Shenzhen) Co.,Ltd.
+ */
+public class TimeServer {
+    private int port;
+
+    public TimeServer(int port) {
+        this.port = port;
+    }
+
+    public void run() throws Exception {
+        EventLoopGroup bossGroup = new NioEventLoopGroup(); // (1)
+        EventLoopGroup workerGroup = new NioEventLoopGroup();
+        try {
+            ServerBootstrap b = new ServerBootstrap(); // (2)
+            b.group(bossGroup, workerGroup)
+                    .channel(NioServerSocketChannel.class) // (3)
+                    .childHandler(new ChannelInitializer<SocketChannel>() { // (4)
+                        @Override
+                        public void initChannel(SocketChannel ch) throws Exception {
+                            ch.pipeline().addLast(new TimeServerHandler());
+                        }
+                    })
+                    .option(ChannelOption.SO_BACKLOG, 128)          // (5)
+                    .childOption(ChannelOption.SO_KEEPALIVE, true); // (6)
+
+            // Bind and start to accept incoming connections.
+            ChannelFuture f = b.bind(port).sync(); // (7)
+
+            // Wait until the server socket is closed.
+            // In this example, this does not happen, but you can do that to gracefully
+            // shut down your server.
+            f.channel().closeFuture().sync();
+        } finally {
+            workerGroup.shutdownGracefully();
+            bossGroup.shutdownGracefully();
+        }
+    }
+
+    public static void main(String[] args) throws Exception {
+        int port = 8080;
+        if (args.length > 0) {
+            port = Integer.parseInt(args[0]);
+        }
+
+        new TimeServer(port).run();
+    }
+}

src/main/java/com/corundumstudio/socketio/demo/time/TimeServerHandler.java

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+package com.corundumstudio.socketio.demo.time;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.ChannelFuture;
+import io.netty.channel.ChannelFutureListener;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelInboundHandlerAdapter;
+
+import java.sql.Time;
+
+/**
+ * TODO :
+ *
+ * @author ye.jf
+ * @version 0.1.0
+ * @date 2022/1/1 14:55
+ * @copyright Wonhigh Information Technology (Shenzhen) Co.,Ltd.
+ */
+public class TimeServerHandler extends ChannelInboundHandlerAdapter {
+
+    @Override
+    public void channelActive(final ChannelHandlerContext ctx) { // (1)
+        //忽略任何接收到的数据,建立连接后立即返回
+        System.out.println("TimeServerHandler channelActive" );
+        final ByteBuf time = ctx.alloc().buffer(4); // (2)
+        time.writeInt((int) (System.currentTimeMillis() / 1000L + 2208988800L));
+
+        final ChannelFuture f = ctx.writeAndFlush(time); // (3)
+        f.addListener(new ChannelFutureListener() {
+            @Override
+            public void operationComplete(ChannelFuture future) {
+                assert f == future;
+                ctx.close();
+            }
+        }); // (4)
+    }
+
+    @Override
+    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
+        cause.printStackTrace();
+        ctx.close();
+    }
+
+}