Documenting source code.

@@ -17,7 +17,7 @@ public class HeartbeatInitializer extends ChannelInitializer<Channel> {
     @Override
     protected void initChannel(Channel ch) throws Exception {
         ch.pipeline()
-                //五秒没有收到消息
+                //五秒没有收到消息 将IdleStateHandler 添加到 ChannelPipeline 中
                 .addLast(new IdleStateHandler(5, 0, 0))
                 .addLast(new HeartbeatDecoder())
                 .addLast(new HeartBeatSimpleHandle());