Add UptimeServer and adjust UptimeClient's code style.

Motivation:

Uptime example is lack of server.
UptimeClient's code style is a little bit different from others, which make reader feel confused.
We don't need to create a new Bootstrap instance each time client reconnect to server.

Modification:

Add UptimeServer and UptimeServerHandler which simply accept all connection and discard all message.
Change UptimeClient's code style.
Share a single Bootstrap instance.

Result:

Uptime server support.
Consistent code style.
Single Bootstrap for all reconnection.

Author: kennylbj

Diff for: example/src/main/java/io/netty/example/uptime/UptimeClient.java

@@ -38,34 +38,27 @@ public final class UptimeClient {
     // Sleep 5 seconds before a reconnection attempt.
     static final int RECONNECT_DELAY = Integer.parseInt(System.getProperty("reconnectDelay", "5"));
     // Reconnect when the server sends nothing for 10 seconds.
-    static final int READ_TIMEOUT = Integer.parseInt(System.getProperty("readTimeout", "10"));
+    private static final int READ_TIMEOUT = Integer.parseInt(System.getProperty("readTimeout", "10"));
 
     private static final UptimeClientHandler handler = new UptimeClientHandler();
+    private static final Bootstrap bs = new Bootstrap();
 
     public static void main(String[] args) throws Exception {
-        configureBootstrap(new Bootstrap()).connect();
+        EventLoopGroup group = new NioEventLoopGroup();
+        bs.group(group)
+                .channel(NioSocketChannel.class)
+                .remoteAddress(HOST, PORT)
+                .handler(new ChannelInitializer<SocketChannel>() {
+                    @Override
+                    protected void initChannel(SocketChannel ch) throws Exception {
+                        ch.pipeline().addLast(new IdleStateHandler(READ_TIMEOUT, 0, 0), handler);
+                    }
+                });
+        bs.connect();
     }
 
-    private static Bootstrap configureBootstrap(Bootstrap b) {
-        return configureBootstrap(b, new NioEventLoopGroup());
-    }
-
-    static Bootstrap configureBootstrap(Bootstrap b, EventLoopGroup g) {
-        b.group(g)
-         .channel(NioSocketChannel.class)
-         .remoteAddress(HOST, PORT)
-         .handler(new ChannelInitializer<SocketChannel>() {
-             @Override
-             public void initChannel(SocketChannel ch) throws Exception {
-                 ch.pipeline().addLast(new IdleStateHandler(READ_TIMEOUT, 0, 0), handler);
-             }
-         });
-
-        return b;
-    }
-
-    static void connect(Bootstrap b) {
-        b.connect().addListener(new ChannelFutureListener() {
+    static void connect() {
+        bs.connect().addListener(new ChannelFutureListener() {
             @Override
             public void operationComplete(ChannelFuture future) throws Exception {
                 if (future.cause() != null) {

Diff for: example/src/main/java/io/netty/example/uptime/UptimeClientHandler.java

@@ -15,10 +15,8 @@
  */
 package io.netty.example.uptime;
 
-import io.netty.bootstrap.Bootstrap;
 import io.netty.channel.ChannelHandler.Sharable;
 import io.netty.channel.ChannelHandlerContext;
-import io.netty.channel.EventLoop;
 import io.netty.channel.SimpleChannelInboundHandler;
 import io.netty.handler.timeout.IdleState;
 import io.netty.handler.timeout.IdleStateEvent;
@@ -70,12 +68,11 @@ public void channelInactive(final ChannelHandlerContext ctx) {
     public void channelUnregistered(final ChannelHandlerContext ctx) throws Exception {
         println("Sleeping for: " + UptimeClient.RECONNECT_DELAY + 's');
 
-        final EventLoop loop = ctx.channel().eventLoop();
-        loop.schedule(new Runnable() {
+        ctx.channel().eventLoop().schedule(new Runnable() {
             @Override
             public void run() {
                 println("Reconnecting to: " + UptimeClient.HOST + ':' + UptimeClient.PORT);
-                UptimeClient.connect(UptimeClient.configureBootstrap(new Bootstrap(), loop));
+                UptimeClient.connect();
             }
         }, UptimeClient.RECONNECT_DELAY, TimeUnit.SECONDS);
     }

Diff for: example/src/main/java/io/netty/example/uptime/UptimeServer.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2017 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.example.uptime;
+
+import io.netty.bootstrap.ServerBootstrap;
+import io.netty.channel.ChannelFuture;
+import io.netty.channel.ChannelInitializer;
+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;
+
+/**
+ * Uptime server is served as a connection server.
+ * So it simply discards all message received.
+ */
+public final class UptimeServer {
+    private static final int PORT = Integer.parseInt(System.getProperty("port", "8080"));
+    private static final UptimeServerHandler handler = new UptimeServerHandler();
+
+    private UptimeServer() {
+    }
+
+    public static void main(String[] args) throws Exception {
+
+        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
+        EventLoopGroup 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
+                        public void initChannel(SocketChannel ch) {
+                            ch.pipeline().addLast(handler);
+                        }
+                    });
+
+            // Bind and start to accept incoming connections.
+            ChannelFuture f = b.bind(PORT).sync();
+
+            // 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();
+        }
+    }
+}

Diff for: example/src/main/java/io/netty/example/uptime/UptimeServerHandler.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2017 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.example.uptime;
+
+import io.netty.channel.ChannelHandler.Sharable;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.SimpleChannelInboundHandler;
+
+@Sharable
+public class UptimeServerHandler extends SimpleChannelInboundHandler<Object> {
+    @Override
+    public void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
+        // discard
+    }
+
+    @Override
+    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
+        // Close the connection when an exception is raised.
+        cause.printStackTrace();
+        ctx.close();
+    }
+}

Diff for: run-example.sh

@@ -38,6 +38,7 @@ EXAMPLE_MAP=(
   'memcache-binary-client:io.netty.example.memcache.binary.MemcacheClient'
   'stomp-client:io.netty.example.stomp.StompClient'
   'uptime-client:io.netty.example.uptime.UptimeClient'
+  'uptime-server:io.netty.example.uptime.UptimeServer'
   'sctpecho-client:io.netty.example.sctp.SctpEchoClient'
   'sctpecho-server:io.netty.example.sctp.SctpEchoServer'
   'localecho:io.netty.example.localecho.LocalEcho'