wing-netty
这可能是目前最透彻的Netty原理架构解析
这可能是⽬前最透彻的Netty原理架构解析本⽂基于 Netty 4.1 展开介绍相关理论模型，使⽤场景，基本组件、整体架构，知其然且知其所以然，希望给⼤家在实际开发实践、学习开源项⽬⽅⾯提供参考。
Netty 是⼀个异步事件驱动的⽹络应⽤程序框架，⽤于快速开发可维护的⾼性能协议服务器和客户端。
JDK 原⽣ NIO 程序的问题JDK 原⽣也有⼀套⽹络应⽤程序 API，但是存在⼀系列问题，主要如下：NIO 的类库和 API 繁杂，使⽤⿇烦。
你需要熟练掌握 Selector、ServerSocketChannel、SocketChannel、ByteBuffer 等。
需要具备其他的额外技能做铺垫。
例如熟悉 Java 多线程编程，因为 NIO 编程涉及到 Reactor 模式，你必须对多线程和⽹路编程⾮常熟悉，才能编写出⾼质量的 NIO 程序。
可靠性能⼒补齐，开发⼯作量和难度都⾮常⼤。
例如客户端⾯临断连重连、⽹络闪断、半包读写、失败缓存、⽹络拥塞和异常码流的处理等等。
NIO 编程的特点是功能开发相对容易，但是可靠性能⼒补齐⼯作量和难度都⾮常⼤。
JDK NIO 的 Bug。
例如臭名昭著的 Epoll Bug，它会导致 Selector 空轮询，最终导致 CPU 100%。
官⽅声称在 JDK 1.6 版本的 update 18 修复了该问题，但是直到 JDK 1.7 版本该问题仍旧存在，只不过该 Bug 发⽣概率降低了⼀些⽽已，它并没有被根本解决。
Netty 的特点Netty 对 JDK ⾃带的 NIO 的 API 进⾏封装，解决上述问题，主要特点有：设计优雅，适⽤于各种传输类型的统⼀ API 阻塞和⾮阻塞 Socket；基于灵活且可扩展的事件模型，可以清晰地分离关注点；⾼度可定制的线程模型 - 单线程，⼀个或多个线程池；真正的⽆连接数据报套接字⽀持（⾃ 3.1 起）。
使⽤⽅便，详细记录的 Javadoc，⽤户指南和⽰例；没有其他依赖项，JDK 5（Netty 3.x）或 6（Netty 4.x）就⾜够了。
netty serverbootstrap 参数-概述说明以及解释
netty serverbootstrap 参数-概述说明以及解释1.引言1.1 概述Netty是一个开源的、高性能、异步事件驱动的网络应用框架，它提供了简单而强大的API，使得网络编程变得更加容易。
Netty提供了一种简单的方式来处理复杂的网络通信，包括TCP、UDP和HTTP等协议。
在Netty中，ServerBootstrap是用于配置服务器端的主要类之一，它提供了一系列参数来配置服务器端的各种属性，以便于用户根据自身需求进行定制。
本文将对Netty框架进行简要介绍，并重点讨论ServerBootstrap的参数配置，以及如何根据实际需求进行参数的调整和优化。
通过对ServerBootstrap参数的详细解释和示例，读者可以更好地了解Netty框架的使用和定制，从而在实际应用中更好地发挥其优势和性能。
1.2 文章结构本文将分为三个部分进行讨论：引言、正文和结论。
在引言部分，我们将对文章的背景和重要性进行概述，介绍本文的结构以及研究的目的。
在正文部分，我们将首先对Netty框架进行简要介绍，了解其在网络编程中的重要性和应用场景。
接着我们将深入探讨ServerBootstrap参数的作用和功能，详细解析各个参数的含义和配置方式，帮助读者更好地理解和应用Netty框架。
在结论部分，我们将对整篇文章进行总结，提出一些应用建议并展望未来Netty框架的发展方向，为读者提供更深入的思考和研究方向。
1.3 目的:在本文中，我们的目的是通过详细讲解Netty框架中ServerBootstrap参数的作用和配置方法，帮助读者更好地理解和掌握Netty框架，在实际项目开发中更加灵活地配置ServerBootstrap，提高网络编程的效率和性能。
通过对参数的深入理解和应用，读者可以优化自己的网络通信系统，满足不同的需求和场景，为项目的发展和稳定性提供技术支持。
同时，我们也希望通过本文的介绍，激发读者对网络编程的兴趣，提升其技术水平和实践能力，为未来的网络开发工作打下坚实基础。
netty源码编译
netty源码编译Netty是一种高性能的、异步的、事件驱动的网络编程框架。
它提供了简单而强大的API，可以帮助开发人员更轻松地构建各种网络应用程序。
Netty的核心是一个基于NIO的异步事件编程框架，可以更好地利用系统资源，提高网络应用程序的性能。
在本文中，我们将详细介绍如何从源码编译Netty。
首先，我们需要准备编译Netty所需的工具和环境。
一、准备工作要编译Netty源码，我们需要安装以下工具和环境：1. JDK：Netty是用Java编写的，因此我们需要安装JDK。
建议使用JDK 8或更高版本。
2. Git：我们需要使用Git来获取Netty的源代码。
安装Git并配置好环境变量。
3. Maven：Netty使用Maven作为构建工具，因此我们需要安装Maven并配置好环境变量。
4. IDE：你可以选择使用任何你熟悉的Java开发IDE，如IntelliJ IDEA或Eclipse。
二、获取源码1.打开终端或命令提示符，切换到一个你准备存放源码的目录。
2. 运行以下命令来克隆Netty的源代码仓库：```shell```这将会获取Netty的最新源码。
三、编译源码1. 打开终端或命令提示符，切换到Netty源码目录。
2.运行以下命令来开始编译：```shellmvn clean install -DskipTests```这将会使用Maven编译Netty的源码。
`-DskipTests`参数是可选的，用于跳过运行单元测试。
编译完成后，你可以在`target`目录中找到编译生成的JAR包。
四、使用IDE开发如果你想使用IDE来开发Netty源码，你可以导入源码到你的开发IDE中。
1. 打开你的IDE，并打开Netty源码目录作为项目。
2.根据IDE的不同，可能需要执行一些配置步骤来正确导入项目。
请参考你的IDE文档来完成这些步骤。
3. 一旦项目导入成功，你就可以开始在IDE中开发Netty源码了。
netty在项目中的应用场景
netty在项目中的应用场景Netty是一个高性能、异步事件驱动的网络应用框架，在现代互联网应用开发中具有广泛的应用场景。
下面介绍Netty在项目中常见的应用场景：**1. 服务器间高效通信**作为一个高性能的网络框架，Netty被广泛应用于服务器间的通信，如RMI、RPC、HTTP等。
与传统的通信方式相比，Netty采用异步I/O模型实现了高并发、低延迟的网络通信。
同时，Netty支持多协议、多应用场景，可无缝集成第三方的JSON或XML序列化工具。
因此在大型分布式系统、微服务框架等场景中，Netty成为了首选的通信框架之一。
**2. 实时通信系统**Netty支持Websocket和HTTP长连接等技术，使得实时通信系统的开发更加简单高效。
实时通信系统比如在线聊天室、游戏平台、视频会议等，需要低延迟、高可靠性的网络传输机制。
同时，因为具有非常大的用户数和消息量，这类应用也需要支持负载均衡、消息分发等功能。
Netty因其高性能、可扩展性和可配置性等特点，在实时通信系统中得到广泛应用。
**3. 代理服务器**Netty可以作为代理服务器实现TCP、UDP等协议的代理。
代理服务器作为应用层与网络层之间的中间人，在网络应用中起到重要的作用。
它可以实现负载均衡、流量控制、数据加密和解密等功能，同时也可以实现流量优化和缓存等机制。
Netty在代理服务器中也得到了广泛应用，比如Squid、Apache Traffic Server等都采用了Netty。
**4. 高并发高吞吐量的Web服务器**Netty也可以作为Web服务器来使用。
Netty支持HTTP协议和HTTPS协议的处理，它的高并发、高吞吐量的特点可以满足各种Web应用的需求。
同时，Netty支持多线程和多核CPU的优化，可以充分利用硬件资源进行并发处理，提高Web服务器的性能和稳定性。
**5. 非阻塞式消息处理系统**Netty支持非阻塞式消息处理机制，可以轻松地实现异步消息的传输和处理。
netty应用案例
netty应用案例Netty是一个高性能的网络通信框架，被广泛应用于各种领域。
下面我将从多个角度给出一些Netty的应用案例。
1. 服务器开发，Netty在服务器开发中得到了广泛应用。
它提供了高性能的网络通信能力，可以处理大量的并发连接。
很多大型互联网公司的服务器后端都使用了Netty，例如游戏服务器、即时通讯服务器、实时数据推送服务器等。
2. 分布式系统，Netty可以作为分布式系统中的通信框架，用于不同节点之间的数据传输和通信。
例如，分布式缓存系统、分布式数据库系统等都可以使用Netty来实现节点之间的通信。
3. 实时数据处理，Netty的高性能和低延迟特性使其在实时数据处理领域得到了广泛应用。
例如，金融领域的实时行情系统、实时交易系统等都可以使用Netty来处理高并发的实时数据。
4. IoT（物联网）应用，Netty可以用于构建物联网平台，用于设备之间的通信和数据传输。
例如，智能家居系统、智能工厂系统等都可以使用Netty来实现设备之间的通信。
5. 高性能代理服务器，Netty可以作为代理服务器的核心框架，用于实现高性能的代理功能。
例如，反向代理服务器、负载均衡服务器等都可以使用Netty来实现。
6. 即时通讯应用，Netty的高性能和可靠性使其成为构建即时通讯应用的理想选择。
例如，聊天应用、视频通话应用等都可以使用Netty来实现实时通信功能。
总结来说，Netty在各种领域中都有广泛的应用。
它的高性能、可靠性和灵活性使其成为构建高性能网络应用的首选框架。
无论是服务器开发、分布式系统、实时数据处理，还是物联网应用、代理服务器、即时通讯应用，Netty都能提供强大的支持。
Netty 中文用户手册
The Netty Project 3.1 User Guide The Proven Approachto Rapid Network Application Development3.1.5.GA, r1772Preface (iii)1. The Problem (iii)2. The Solution (iii)1. Getting Started (1)1.1. Before Getting Started (1)1.2. Writing a Discard Server (1)1.3. Looking into the Received Data (3)1.4. Writing an Echo Server (4)1.5. Writing a Time Server (5)1.6. Writing a Time Client (7)1.7. Dealing with a Stream-based Transport (8)1.7.1. One Small Caveat of Socket Buffer (8)1.7.2. The First Solution (9)1.7.3. The Second Solution (11)1.8. Speaking in POJO instead of ChannelBuffer (12)1.9. Shutting Down Your Application (15)1.10. Summary (18)2. Architectural Overview (19)2.1. Rich Buffer Data Structure (19)2.2. Universal Asynchronous I/O API (19)2.3. Event Model based on the Interceptor Chain Pattern (20)2.4. Advanced Components for More Rapid Development (21)2.4.1. Codec framework (21)2.4.2. SSL / TLS Support (21)2.4.3. HTTP Implementation (22)2.4.4. Google Protocol Buffer Integration (22)2.5. Summary (22)PrefaceThis guide provides an introduction to Netty and what it is about.1. The ProblemNowadays we use general purpose applications or libraries to communicate with each other. For example, we often use an HTTP client library to retrieve information from a web server and to invoke a remote procedure call via web services.However, a general purpose protocol or its implementation sometimes does not scale very well. It is like we don't use a general purpose HTTP server to exchange huge files, e-mail messages, and near-realtime messages such as financial information and multiplayer game data. What's required is a highly optimized protocol implementation which is dedicated to a special purpose. For example, you might want to implement an HTTP server which is optimized for AJAX-based chat application, media streaming, or large file transfer. You could even want to design and implement a whole new protocol which is precisely tailored to your need.Another inevitable case is when you have to deal with a legacy proprietary protocol to ensure the interoperability with an old system. What matters in this case is how quickly we can implement that protocol while not sacrificing the stability and performance of the resulting application.2. The SolutionThe Netty project is an effort to provide an asynchronous event-driven network application framework and tooling for the rapid development of maintainable high-performance high-scalability protocol servers and clients.In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server development.'Quick and easy' does not mean that a resulting application will suffer from a maintainability or a performance issue. Netty has been designed carefully with the experiences earned from the implementation of a lot of protocols such as FTP, SMTP, HTTP, and various binary and text-based legacy protocols. As a result, Netty has succeeded to find a way to achieve ease of development, performance, stability, and flexibility without a compromise.Some users might already have found other network application framework that claims to have the same advantage, and you might want to ask what makes Netty so different from them. The answer is the philosophy where it is built on. Netty is designed to give you the most comfortable experience both in terms of the API and the implementation from the day one. It is not something tangible but you will realize that this philosophy will make your life much easier as you read this guide and play with Netty.Chapter 1.Getting StartedThis chapter tours around the core constructs of Netty with simple examples to let you get started quickly. You will be able to write a client and a server on top of Netty right away when you are at the end of this chapter.If you prefer top-down approach in learning something, you might want to start from Chapter 2, Architectural Overview and get back here.1.1. Before Getting StartedThe minimum requirements to run the examples which are introduced in this chapter are only two; the latest version of Netty and JDK 1.5 or above. The latest version of Netty is available in the project download page. To download the right version of JDK, please refer to your preferred JDK vendor's web site.Is that all? To tell the truth, you should find these two are just enough to implement almost any type of protocols. Otherwise, please feel free to contact the Netty project community and let us know what's missing.At last but not least, please refer to the API reference whenever you want to know more about the classes introduced here. All class names in this document are linked to the online API reference for your convenience. Also, please don't hesitate to contact the Netty project community and let us know if there's any incorrect information, errors in grammar and typo, and if you have a good idea to improve the documentation.1.2. Writing a Discard ServerThe most simplistic protocol in the world is not 'Hello, World!' but DISCARD. It's a protocol which discards any received data without any response.To implement the DISCARD protocol, the only thing you need to do is to ignore all received data. Let us start straight from the handler implementation, which handles I/O events generated by Netty.Writing a Discard ServerChannelPipelineCoverage annotates a handler type to tell if the handler instance of the annotated type can be shared by more than one Channel (and its associated ChannelPipeline).DiscardServerHandler does not manage any stateful information, and therefore it is annotated with the value "all".DiscardServerHandler extends SimpleChannelHandler, which is an implementation of ChannelHandler. SimpleChannelHandler provides various event handler methods that you can override. For now, it is just enough to extend SimpleChannelHandler rather than to implement the handler interfaces by yourself.We override the messageReceived event handler method here. This method is called with a MessageEvent, which contains the received data, whenever new data is received from a client. In this example, we ignore the received data by doing nothing to implement the DISCARD protocol.exceptionCaught event handler method is called with an ExceptionEvent when an exception was raised by Netty due to I/O error or by a handler implementation due to the exception thrown while processing events. In most cases, the caught exception should be logged and its associated channel should be closed here, although the implementation of this method can be different depending on what you want to do to deal with an exceptional situation. For example, you might want to send a response message with an error code before closing the connection.So far so good. We have implemented the first half of the DISCARD server. What's left now is to write the main method which starts the server with the DiscardServerHandler.Looking into the Received DataChannelFactory is a factory which creates and manages Channel s and its related resources. It processes all I/O requests and performs I/O to generate ChannelEvent s. Netty provides various ChannelFactory implementations. We are implementing a server-side application in this example, and therefore NioServerSocketChannelFactory was used. Another thing to note is that it does not create I/O threads by itself. It is supposed to acquire threads from the thread pool you specified in the constructor, and it gives you more control over how threads should be managed in the environment where your application runs, such as an application server with a security manager.ServerBootstrap is a helper class that sets up a server. You can set up the server using a Channel directly. However, please note that this is a tedious process and you do not need to do that in most cases.Here, we add the DiscardServerHandler to the default ChannelPipeline. Whenevera new connection is accepted by the server, a new ChannelPipeline will be created fora newly accepted Channel and all the ChannelHandler s added here will be added tothe new ChannelPipeline. It's just like a shallow-copy operation; all Channel and their ChannelPipeline s will share the same DiscardServerHandler instance.You can also set the parameters which are specific to the Channel implementation. We are writing a TCP/IP server, so we are allowed to set the socket options such as tcpNoDelay and keepAlive.Please note that the "child." prefix was added to all options. It means the options will be applied to the accepted Channel s instead of the options of the ServerSocketChannel. You could do the following to set the options of the ServerSocketChannel:We are ready to go now. What's left is to bind to the port and to start the server. Here, we bind to the port 8080 of all NICs (network interface cards) in the machine. You can now call the bind method as many times as you want (with different bind addresses.)Congratulations! You've just finished your first server on top of Netty.1.3. Looking into the Received DataNow that we have written our first server, we need to test if it really works. The easiest way to test it is to use the telnet command. For example, you could enter "telnet localhost 8080" in the command line and type something.However, can we say that the server is working fine? We cannot really know that because it is a discard server. You will not get any response at all. To prove it is really working, let us modify the server to print what it has received.We already know that MessageEvent is generated whenever data is received and the messageReceived handler method will be invoked. Let us put some code into the messageReceived method of the DiscardServerHandler:It is safe to assume the message type in socket transports is always ChannelBuffer.ChannelBuffer is a fundamental data structure which stores a sequence of bytes in Netty. It's similar to NIO ByteBuffer, but it is easier to use and more flexible. For example, Netty allows you to create a composite ChannelBuffer which combines multiple ChannelBuffer s reducing the number of unnecessary memory copy.Although it resembles to NIO ByteBuffer a lot, it is highly recommended to refer to the API reference. Learning how to use ChannelBuffer correctly is a critical step in using Netty without difficulty.If you run the telnet command again, you will see the server prints what has received.The full source code of the discard server is located in the ty.example.discard package of the distribution.1.4. Writing an Echo ServerSo far, we have been consuming data without responding at all. A server, however, is usually supposed to respond to a request. Let us learn how to write a response message to a client by implementing the ECHO protocol, where any received data is sent back.The only difference from the discard server we have implemented in the previous sections is that it sends the received data back instead of printing the received data out to the console. Therefore, it is enough again to modify the messageReceived method:A ChannelEvent object has a reference to its associated Channel. Here, the returned Channelrepresents the connection which received the MessageEvent. We can get the Channel and call the write method to write something back to the remote peer.If you run the telnet command again, you will see the server sends back whatever you have sent to it. The full source code of the echo server is located in the ty.example.echo package of the distribution.1.5. Writing a Time ServerThe protocol to implement in this section is the TIME protocol. It is different from the previous examples in that it sends a message, which contains a 32-bit integer, without receiving any requests and loses the connection once the message is sent. In this example, you will learn how to construct and send a message, and to close the connection on completion.Because we are going to ignore any received data but to send a message as soon as a connection is established, we cannot use the messageReceived method this time. Instead, we should override the channelConnected method. The following is the implementation:As explained, channelConnected method will be invoked when a connection is established. Let us write the 32-bit integer that represents the current time in seconds here.To send a new message, we need to allocate a new buffer which will contain the message. We are going to write a 32-bit integer, and therefore we need a ChannelBuffer whose capacity is 4 bytes. The ChannelBuffers helper class is used to allocate a new buffer. Besides the buffer method, ChannelBuffers provides a lot of useful methods related to the ChannelBuffer. For more information, please refer to the API reference.On the other hand, it is a good idea to use static imports for ChannelBuffers:As usual, we write the constructed message.But wait, where's the flip? Didn't we used to call ByteBuffer.flip() before sending a message in NIO? ChannelBuffer does not have such a method because it has two pointers; one for read operations and the other for write operations. The writer index increases when you write something to a ChannelBuffer while the reader index does not change. The reader index and the writer index represents where the message starts and ends respectively.In contrast, NIO buffer does not provide a clean way to figure out where the message content starts and ends without calling the flip method. You will be in trouble when you forget to flip the buffer because nothing or incorrect data will be sent. Such an error does not happen in Netty because we have different pointer for different operation types. You will find it makes your life much easier as you get used to it -- a life without flipping out!Another point to note is that the write method returns a ChannelFuture. A ChannelFuture represents an I/O operation which has not yet occurred. It means, any requested operation might not have been performed yet because all operations are asynchronous in Netty. For example, the following code might close the connection even before a message is sent:Therefore, you need to call the close method after the ChannelFuture, which was returned by the write method, notifies you when the write operation has been done. Please note that, close might not close the connection immediately, and it returns a ChannelFuture.How do we get notified when the write request is finished then? This is as simple as addinga ChannelFutureListener to the returned ChannelFuture. Here, we created a newanonymous ChannelFutureListener which closes the Channel when the operation is done.Alternatively, you could simplify the code using a pre-defined listener:1.6. Writing a Time ClientUnlike DISCARD and ECHO servers, we need a client for the TIME protocol because a human cannot translate a 32-bit binary data into a date on a calendar. In this section, we discuss how to make sure the server works correctly and learn how to write a client with Netty.The biggest and only difference between a server and a client in Netty is that different Bootstrap and ChannelFactory are required. Please take a look at the following code:NioClientSocketChannelFactory, instead of NioServerSocketChannelFactory was used to create a client-side Channel.Dealing with a Stream-based TransportClientBootstrap is a client-side counterpart of ServerBootstrap.Please note that there's no "child." prefix. A client-side SocketChannel does not have a parent.We should call the connect method instead of the bind method.As you can see, it is not really different from the server side startup. What about the ChannelHandler implementation? It should receive a 32-bit integer from the server, translate it into a human readable format, print the translated time, and close the connection:It looks very simple and does not look any different from the server side example. However, this handler sometimes will refuse to work raising an IndexOutOfBoundsException. We discuss why this happens in the next section.1.7. Dealing with a Stream-based Transport1.7.1. One Small Caveat of Socket BufferIn a stream-based transport such as TCP/IP, received data is stored into a socket receive buffer. Unfortunately, the buffer of a stream-based transport is not a queue of packets but a queue of bytes. It means, even if you sent two messages as two independent packets, an operating system will not treat them as two messages but as just a bunch of bytes. Therefore, there is no guarantee that what you read is exactly what your remote peer wrote. For example, let us assume that the TCP/IP stack of an operating system has received three packets:Because of this general property of a stream-based protocol, there's high chance of reading them in the following fragmented form in your application:Therefore, a receiving part, regardless it is server-side or client-side, should defrag the received data into one or more meaningful frames that could be easily understood by the application logic. In case of the example above, the received data should be framed like the following:1.7.2. The First SolutionNow let us get back to the TIME client example. We have the same problem here. A 32-bit integer is a very small amount of data, and it is not likely to be fragmented often. However, the problem is that it can be fragmented, and the possibility of fragmentation will increase as the traffic increases.The simplistic solution is to create an internal cumulative buffer and wait until all 4 bytes are received into the internal buffer. The following is the modified TimeClientHandler implementation that fixes the problem:This time, "one"was used as the value of the ChannelPipelineCoverage annotation.It's because the new TimeClientHandler has to maintain the internal buffer and therefore cannot serve multiple Channel s. If an instance of TimeClientHandler is shared by multiple Channel s (and consequently multiple ChannelPipeline s), the content of the buf will be corrupted.A dynamic buffer is a ChannelBuffer which increases its capacity on demand. It's very usefulwhen you don't know the length of the message.First, all received data should be cumulated into buf.And then, the handler must check if buf has enough data, 4 bytes in this example, and proceed to the actual business logic. Otherwise, Netty will call the messageReceived method again when more data arrives, and eventually all 4 bytes will be cumulated.There's another place that needs a fix. Do you remember that we added a TimeClientHandler instance to the default ChannelPipeline of the ClientBootstrap? It means one same TimeClientHandler instance is going to handle multiple Channel s and consequently the data will be corrupted. To create a new TimeClientHandler instance per Channel, we have to implement a ChannelPipelineFactory:Now let us replace the following lines of TimeClient:with the following:It might look somewhat complicated at the first glance, and it is true that we don't need to introduce TimeClientPipelineFactory in this particular case because TimeClient creates only one connection.However, as your application gets more and more complex, you will almost always end up with writing a ChannelPipelineFactory, which yields much more flexibility to the pipeline configuration.1.7.3. The Second SolutionAlthough the first solution has resolved the problem with the TIME client, the modified handler does not look that clean. Imagine a more complicated protocol which is composed of multiple fields such as a variable length field. Your ChannelHandler implementation will become unmaintainable very quickly.As you may have noticed, you can add more than one ChannelHandler to a ChannelPipeline, and therefore, you can split one monolithic ChannelHandler into multiple modular ones to reduce the complexity of your application. For example, you could split TimeClientHandler into two handlers:•TimeDecoder which deals with the fragmentation issue, and•the initial simple version of TimeClientHandler.Fortunately, Netty provides an extensible class which helps you write the first one out of the box:There's no ChannelPipelineCoverage annotation this time because FrameDecoder is already annotated with "one".FrameDecoder calls decode method with an internally maintained cumulative buffer whenever new data is received.If null is returned, it means there's not enough data yet. FrameDecoder will call again when there is a sufficient amount of data.If non-null is returned, it means the decode method has decoded a message successfully.FrameDecoder will discard the read part of its internal cumulative buffer. Please remember that you don't need to decode multiple messages. FrameDecoder will keep calling the decoder method until it returns null.If you are an adventurous person, you might want to try the ReplayingDecoder which simplifies the decoder even more. You will need to consult the API reference for more information though.Additionally, Netty provides out-of-the-box decoders which enables you to implement most protocols very easily and helps you avoid from ending up with a monolithic unmaintainable handler implementation. Please refer to the following packages for more detailed examples:•ty.example.factorial for a binary protocol, and•ty.example.telnet for a text line-based protocol.1.8. Speaking in POJO instead of ChannelBufferAll the examples we have reviewed so far used a ChannelBuffer as a primary data structure of a protocol message. In this section, we will improve the TIME protocol client and server example to use a POJO instead of a ChannelBuffer.The advantage of using a POJO in your ChannelHandler is obvious; your handler becomes more maintainable and reusable by separating the code which extracts information from ChannelBuffer out from the handler. In the TIME client and server examples, we read only one 32-bit integer and it is not a major issue to use ChannelBuffer directly. However, you will find it is necessary to make the separation as you implement a real world protocol.First, let us define a new type called UnixTime.We can now revise the TimeDecoder to return a UnixTime instead of a ChannelBuffer.FrameDecoder and ReplayingDecoder allow you to return an object of any type. If they were restricted to return only a ChannelBuffer, we would have to insert another ChannelHandler which transforms a ChannelBuffer into a UnixTime.With the updated decoder, the TimeClientHandler does not use ChannelBuffer anymore:Much simpler and elegant, right? The same technique can be applied on the server side. Let us update the TimeServerHandler first this time:Now, the only missing piece is the ChannelHandler which translates a UnixTime back into a ChannelBuffer. It's much simpler than writing a decoder because there's no need to deal with packet fragmentation and assembly when encoding a message.The ChannelPipelineCoverage value of an encoder is usually "all" because this encoder is stateless. Actually, most encoders are stateless.An encoder overrides the writeRequested method to intercept a write request. Please note that the MessageEvent parameter here is the same type which was specified in messageReceived but they are interpreted differently. A ChannelEvent can be either an upstream or downstreamevent depending on the direction where the event flows. For instance, a MessageEvent can be an upstream event when called for messageReceived or a downstream event when called for writeRequested. Please refer to the API reference to learn more about the difference between a upstream event and a downstream event.Once done with transforming a POJO into a ChannelBuffer, you should forward the new buffer to the previous ChannelDownstreamHandler in the ChannelPipeline. Channels provides various helper methods which generates and sends a ChannelEvent. In this example, Channels.write(...)method creates a new MessageEvent and sends it to the previous ChannelDownstreamHandler in the ChannelPipeline.On the other hand, it is a good idea to use static imports for Channels:The last task left is to insert a TimeEncoder into the ChannelPipeline on the server side, and it is left as a trivial exercise.1.9. Shutting Down Your ApplicationIf you ran the TimeClient, you must have noticed that the application doesn't exit but just keep running doing nothing. Looking from the full stack trace, you will also find a couple I/O threads are running. To shut down the I/O threads and let the application exit gracefully, you need to release the resources allocated by ChannelFactory.The shutdown process of a typical network application is composed of the following three steps:1.Close all server sockets if there are any,2.Close all non-server sockets (i.e. client sockets and accepted sockets) if there are any, and3.Release all resources used by ChannelFactory.To apply the three steps above to the TimeClient, TimeClient.main()could shut itself down gracefully by closing the only one client connection and releasing all resources used by ChannelFactory:The connect method of ClientBootstrap returns a ChannelFuture which notifies whena connection attempt succeeds or fails. It also has a reference to the Channel which is associatedwith the connection attempt.Wait for the returned ChannelFuture to determine if the connection attempt was successful or not.If failed, we print the cause of the failure to know why it failed. the getCause()method of ChannelFuture will return the cause of the failure if the connection attempt was neither successful nor cancelled.Now that the connection attempt is over, we need to wait until the connection is closed by waiting for the closeFuture of the Channel. Every Channel has its own closeFuture so that you are notified and can perform a certain action on closure.Even if the connection attempt has failed the closeFuture will be notified because the Channel will be closed automatically when the connection attempt fails.All connections have been closed at this point. The only task left is to release the resources being used by ChannelFactory. It is as simple as calling its releaseExternalResources() method.All resources including the NIO Selector s and thread pools will be shut down and terminated automatically.Shutting down a client was pretty easy, but how about shutting down a server? You need to unbind from the port and close all open accepted connections. To do this, you need a data structure that keeps track of the list of active connections, and it's not a trivial task. Fortunately, there is a solution, ChannelGroup. ChannelGroup is a special extension of Java collections API which represents a set of open Channel s. If a Channel is added to a ChannelGroup and the added Channel is closed, the closed Channel is removed from its ChannelGroup automatically. You can also perform an operation on all Channel s in the same group. For instance, you can close all Channel s in a ChannelGroup when you shut down your server.To keep track of open sockets, you need to modify the TimeServerHandler to add a new open Channel to the global ChannelGroup, TimeServer.allChannels:。
netty 底层原理
netty 底层原理Netty是一种基于Java NIO（非阻塞I/O）的网络编程框架，具有高性能、高可靠性和易于使用的特点。
它的底层原理是通过事件驱动模型来实现高效的网络通信。
Netty的底层原理主要包括以下几个方面：1. Reactor模式：Netty采用了Reactor模式来处理网络事件。
Reactor模式是一种基于事件驱动的设计模式，通过一个或多个事件处理器（也称为事件监听器）来监听事件，并根据不同的事件类型进行相应的处理。
Netty使用了单线程或多线程的方式来处理事件，提高了并发处理能力。
2. Selector选择器：Netty使用了Java NIO中的Selector选择器来实现事件的分发和调度。
Selector是一种高效的多路复用器，可以同时监听多个网络连接的事件，当有事件发生时，Selector会将这些事件分发给相应的事件处理器进行处理。
3. Channel通道：Netty的核心组件是Channel，它代表了一个网络连接，可以进行数据的读写操作。
Channel提供了异步的I/O操作，通过回调机制来处理事件。
Netty的Channel可以分为不同的类型，如SocketChannel、ServerSocketChannel等，每种类型的Channel都有相应的事件处理器。
4. 缓冲区（Buffer）：Netty使用缓冲区来进行数据的读写操作。
缓冲区是一种连续的内存空间，用于存储数据。
Netty使用了零拷贝（Zero-copy）技术，即数据在网络和应用程序之间传输时，不需要进行额外的数据拷贝操作，提高了性能。
5. 线程模型：Netty的线程模型是通过EventLoopGroup来实现的。
EventLoopGroup包含了一组EventLoop，每个EventLoop都负责处理一部分连接的事件。
EventLoop内部使用了线程池来管理线程，通过事件驱动的方式来处理事件。
Netty的线程模型支持多种模式，如单线程模式、多线程模式、主从线程模式等，可以根据应用的需要进行选择。
netty in action 翻译 -回复
netty in action 翻译-回复Netty In Action是一本广受欢迎的网络编程框架Netty的指南和实践手册。
这本书致力于向读者介绍Netty的基本概念、设计模式和最佳实践，以及如何构建高性能和可扩展的网络应用程序。
本文将按照章节顺序，一步一步回答关于Netty的各个方面的问题，以帮助读者更好地理解和应用这个强大的框架。
第一章：Netty–异步和事件驱动的网络应用程序- 什么是异步和事件驱动的网络应用程序？异步和事件驱动是指网络应用程序中不同的工作模式。
异步指的是应用程序不会等待某个操作的完成才继续执行后续操作，而是可以同时处理其他任务。
事件驱动是指应用程序通过监听和响应事件来进行工作，而不是执行预定的顺序或轮询。
- Netty如何实现异步和事件驱动？Netty通过使用Java的NIO（非阻塞IO）和事件循环组件实现异步和事件驱动。
NIO提供了非阻塞的IO操作，使应用程序可以同时处理多个客户端连接。
事件循环组件是Netty的核心部分，负责接收和分发事件，以及执行应用程序逻辑。
第二章：Netty的体系结构- Netty的体系结构是什么样的？Netty的体系结构基于三个主要构建块：Channel、EventLoop和ChannelPipeline。
Channel是Netty的基本抽象，代表一个与远程对等方的连接。
EventLoop是一个处理事件的线程，用于管理Channel的所有IO操作。
ChannelPipeline是一个处理入站和出站数据的操作链。
- 如何使用Channel和EventLoop来实现异步和事件驱动？应用程序通过与Channel交互来进行异步和事件驱动的编程。
通过向Channel注册感兴趣的事件类型，应用程序可以通过EventLoop异步地处理这些事件。
第三章：Netty的编解码器- 什么是编解码器？编解码器是一种将数据从一种格式转换为另一种格式的组件。
在网络应用程序中，编解码器用于将原始字节数据转换为可以读取和处理的对象，以及将对象转换为字节数据进行网络传输。
Netty 中文技术文档
本指南对Netty 进行了介绍并指出其意义所在。
1. 问题现在，我们使用适合一般用途的应用或组件来和彼此通信。
例如，我们常常使用一个HTTP 客户端从远程服务器获取信息或者通过webservices进行远程方法的调用。
然而，一个适合普通目的的协议或其实现并不具备其规模上的扩展性。
例如，我们无法使用一个普通的HTTP服务器进行大型文件，电邮信息的交互，或者处理金融信息和多人游戏数据那种要求准实时消息传递的应用场景。
因此，这些都要求使用一个适用于特殊目的并经过高度优化的协议实现。
例如，你可能想要实现一个对基于AJAX的聊天应用，媒体流或大文件传输进行过特殊优化的HTTP服务器。
你甚至可能想去设计和实现一个全新的，特定于你的需求的通信协议。
另一种无法避免的场景是你可能不得不使用一种专有的协议和原有系统交互。
在这种情况下，你需要考虑的是如何能够快速的开发出这个协议的实现并且同时还没有牺牲最终应用的性能和稳定性。
2. 方案Netty 是一个异步的，事件驱动的网络编程框架和工具，使用Netty可以快速开发出可维护的，高性能、高扩展能力的协议服务及其客户端应用。
也就是说，Netty 是一个基于NIO的客户，服务器端编程框架，使用Netty可以确保你快速和简单的开发出一个网络应用，例如实现了某种协议的客户，服务端应用。
Netty相当简化和流线化了网络应用的编程开发过程，例如，TCP和UDP的socket服务开发。
"快速"和"简单"并不意味着会让你的最终应用产生维护性或性能上的问题。
Netty是一个吸收了多种协议的实现经验，这些协议包括FTP,SMPT,HTTP，各种二进制，文本协议，并经过相当精心设计的项目，最终，Netty成功的找到了一种方式，在保证易于开发的同时还保证了其应用的性能，稳定性和伸缩性。
一些用户可能找到了某些同样声称具有这些特性的编程框架，因此你们可能想问Netty 又有什么不一样的地方。
Netty5入门指南
问题现如今我们使用通用的应用程序或者类库来实现系统之间地互相访问，比如我们经常使用一个HTTP客户端来从web服务器上获取信息，或者通过web service来执行一个远程的调用。
然而，有时候一个通用的协议和他的实现并没有覆盖一些场景。
比如我们无法使用一个通用的HTTP服务器来处理大文件、电子邮件、近实时消息比如财务信息和多人游戏数据。
我们需要一个合适的协议来处理一些特殊的场景。
例如你可以实现一个优化的Ajax的聊天应用、媒体流传输或者是大文件传输的HTTP服务器，你甚至可以自己设计和实现一个新的协议来准确地实现你的需求。
另外不可避免的事情是你不得不处理这些私有协议来确保和原有系统的互通。
这个例子将会展示如何快速实现一个不影响应用程序稳定性和性能的协议。
解决方案Netty是一个提供异步事件驱动的网络应用框架，用以快速开发高性能、高可靠性的网络服务器和客户端程序。
换句话说，Netty是一个NIO框架，使用它可以简单快速地开发网络应用程序，比如客户端和服务端的协议。
Netty大大简化了网络程序的开发过程比如TCP和UDP的 Socket 的开发。
“快速和简单”并不意味着应用程序会有难维护和性能低的问题，Netty是一个精心设计的框架，它从许多协议的实现中吸收了很多的经验比如FTP、SMTP、HTTP、许多二进制和基于文本的传统协议，Netty在不降低开发效率、性能、稳定性、灵活性情况下，成功地找到了解决方案。
有一些用户可能已经发现其他的一些网络框架也声称自己有同样的优势，所以你可能会问是Netty和它们的不同之处。
答案就是Netty的哲学设计理念。
Netty从第一天开始就为用户提供了用户体验最好的API以及实现设计。
正是因为Netty的设计理念，才让我们得以轻松地阅读本指南并使用Netty。
入门指南这个章节会介绍Netty核心的结构，并通过一些简单的例子来帮助你快速入门。
当你读完本章节你马上就可以用Netty写出一个客户端和服务端。
netty 建立连接的调用方法
netty 建立连接的调用方法一、引入Netty依赖我们需要在项目中引入Netty的相关依赖。
可以通过Maven或者Gradle等构建工具进行依赖管理。
以下是一个Maven的示例配置：```xml<dependency><groupId>ty</groupId><artifactId>netty-all</artifactId><version>4.1.68.Final</version></dependency>```二、创建服务端Netty的服务端主要用于监听并接受客户端的连接请求。
我们可以通过以下步骤创建一个简单的Netty服务端：1. 创建一个EventLoopGroup对象，用于处理IO操作。
Netty通过EventLoopGroup来处理事件，包括接受客户端连接、读写数据等。
```javaEventLoopGroup bossGroup = new NioEventLoopGroup(); EventLoopGroup workerGroup = new NioEventLoopGroup();```2. 创建ServerBootstrap对象，并配置相关参数。
ServerBootstrap是Netty用于创建服务端的启动类。
```javaServerBootstrap serverBootstrap = new ServerBootstrap(); serverBootstrap.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).childHandler(newChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ch.pipeline().addLast(new MyServerHandler()); }});```在上述代码中，我们通过group方法指定了bossGroup和workerGroup，channel方法指定了服务端的Channel类型，childHandler方法指定了每个新连接的处理器。
netty addlistener用法 -回复
netty addlistener用法-回复Netty是一个高性能、异步事件驱动的网络编程框架，常用于构建可伸缩和可维护的服务器和客户端应用程序。
在Netty中，有一个非常重要的概念称为"addListener"，它用于向ChannelFuture对象添加一个ChannelFutureListener，以便在操作完成时接收通知和执行相应的逻辑。
本文将以"Netty addListener用法"为主题，详细介绍Netty中addListener方法的用法和原理，并通过实例来说明其在实际开发中的应用。
一、Netty中的addListener方法简介在Netty中，每个IO操作都会返回一个ChannelFuture对象，用于表示操作的异步结果。
通过为ChannelFuture对象添加ChannelFutureListener，我们可以在I/O操作成功或失败时做出相应的响应。
addListener方法即用于向ChannelFuture对象添加一个或多个ChannelFutureListener。
二、addListener方法的使用步骤下面我们逐步介绍如何使用addListener方法，并通过一个实例来说明具体用法。
步骤1：创建一个Netty项目并引入Netty库首先，我们需要创建一个基于Netty的Java项目，并在项目中引入Netty 的相关库。
你可以选择使用Maven、Gradle等构建工具来管理依赖。
步骤2：初始化和配置Netty服务器在创建Netty服务器之前，我们需要进行相关的初始化和配置操作。
具体而言，我们需要创建一个EventLoopGroup、ServerBootstrap以及ChannelInitializer来设置服务器的选项和处理事件的逻辑。
步骤3：添加addListener方法在Netty服务器初始化和启动阶段，我们需要用addListener方法来注册一个ChannelFutureListener，以便在服务器启动成功或失败时做出响应。
netty技术要点
Netty技术要点包括以下几点：1. 心跳机制设计：当网络处于空闲状态持续时间达到T（连续周期T没有读写消息）时，客户端主动发送Ping心跳消息给服务端。
如果在下一个周期T到来时客户端没有收到对方发送到Pong心跳应答消息或者读取到服务端发送到其他业务消息，则心跳失败计数器加1。
每当客户端接收到服务的业务消息或者Pong应答消息时，将心跳失败计数器清零，连续N 此没有接收到服务端的Pong消息或者业务消息，则关闭链路，间隔INTERVAL时间后发起重连操作。
服务端网络空闲状态持续时间达到T后，服务端将心跳失败计数器加1，只要接收到客户端发送到Ping消息或者其他业务消息，计数器请零。
服务端连续N次没有接收到客户端的Ping消息或者其他业务消息，则关闭链路，释放自由，等待客户端重连。
2. 重连机制：如果链路中断，等待INTERVAL时间后，由客户端发起重连操作，如果重连失败，间隔周期INTERVAL后再次发起重连，直到连接成功。
重连失败，客户端必须及时释放自身的资源并打印异常堆栈信息，方便后续的问题定位。
3. 重复登录保护：当客户端握手成功之后，在链路处于正常状态下，不允许客户端重复登录，以防止客户端在异常状态下反复重连导致句柄资源被耗尽。
服务端接收到客户端的握手请求消息之后，首先对IP地址进行合法性检验，如果校验成功，在缓存的地址表中查看客户端是否已经登录，如果已经登录，则拒绝重复登录，返回错误码-1，同时关闭TCP链路，并在服务端的日志中打印握手失败的原因。
服务端主动关闭链路时，清空客户端的地址缓存信息。
4. 消息缓存重发：无论客户端还是服务端，当发生链路中断之后，在链路恢复之前，缓存在消息队列中待发送的消息不能丢失，等链路恢复之后，重新发送这些消息，保证链路中断期间消息不丢失。
考虑到内存溢出的风险，消息缓存队列设置上限，当达到上限之后，应该拒绝继续向该队列添加新的消息。
5. 安全性设计：为了保证整个集群环境的安全，内部长连接采用基于IP地址的安全认证机制，服务端对握手请求消息的IP地址进行合法性校验，如果在白名单之内，则校验通过，否则，拒绝对方连接。
netty应用案例
netty应用案例Netty是一个用于快速开发可扩展的网络应用程序的Java框架。
它的设计目标是提供一个高性能、高速度和可靠的网络服务器和客户端框架。
Netty是一个事件驱动的网络编程框架，通过轻量级的、非阻塞的异步网络通信，提供了快速的数据传输和处理。
下面将介绍几个Netty的应用案例。
1.聊天服务器一个常见的使用Netty的案例是构建一个实时聊天服务器。
Netty可以通过NIO的非阻塞方式处理大量的并发连接，使得用户可以实时地发送和接收消息。
使用Netty可以轻松地实现高性能的聊天服务器，支持多种协议和编解码方式。
2.实时数据流处理Netty可以用于构建实时数据流处理应用程序，比如实时数据分析、实时监控等。
Netty提供了高性能的异步网络通信能力，可以快速地传输大量的数据流，并同时支持高并发连接。
这使得Netty成为处理实时数据流的理想框架。
3.代理服务器Netty可以作为代理服务器的核心框架，用于实现HTTP、HTTPS、SOCKS等多种类型的代理服务器。
Netty提供了高性能的异步网络通信，可以有效地处理代理请求，并将其转发到目标服务器。
同时，Netty支持自定义的编解码器，可以对请求进行解析和编码。
4.游戏服务器Netty在构建游戏服务器方面也有广泛的应用。
Netty的非阻塞和事件驱动的设计使得它能够支持高并发连接和实时的消息传输，非常适合用于构建多人在线游戏服务器。
此外，Netty还提供了一些常用的功能，如心跳检测、断线重连等，方便开发者构建稳定可靠的游戏服务器。
5.分布式系统通信Netty可以作为分布式系统中节点之间通信的框架。
在一个分布式系统中，节点之间需要快速地发送和接收消息，以实现数据同步和协调工作。
Netty提供了高性能的网络通信能力，并支持各种通信协议和编解码方式，使得节点之间的通信变得简单和高效。
在以上应用示例中，Netty都发挥了它异步非阻塞的优势，通过事件驱动的方式处理并发连接，提供了高性能的网络通信能力。
netty channelfuture用法
Netty是一个基于NIO的网络通信框架，旨在帮助开发人员快速、高效地构建网络应用程序。
其中，ChannelFuture作为Netty中重要的概念之一，具有广泛的用途和重要的作用。
本文将介绍Netty中ChannelFuture的基本用法，并结合实际案例进行详细说明，以帮助读者更好地理解和运用该功能。
1. ChannelFuture概述ChannelFuture代表了一个尚未完成的I/O操作。
在Netty中，几乎所有的I/O操作都是异步的，这意味着当一个I/O操作被调用时，并不能立即得到结果。
为了解决这一问题，Netty引入了ChannelFuture的概念，通过它可以注册一个或多个ChannelFutureListener，当I/O操作完成时，这些监听器将被通知，并且可以获取操作结果或者执行相应的操作。
2. ChannelFuture的基本用法在Netty中，ChannelFuture可以通过Channel的write、connect、disconnect等方法来获取。
下面我们以Channel的write方法为例，介绍ChannelFuture的基本用法。
```Channel channel = ...; // 通过某种方式获取一个Channel实例ChannelFuture future =channel.write(Unpooled.wrappedBuffer("Hello,Netty".getBytes()) );future.addListener(new ChannelFutureListener() {Overridepublic void operationComplete(ChannelFuture future) {if (future.isSuccess()) {System.out.println("Write success");} else {System.err.println("Write f本人led");future.cause().printStackTrace();}}});```在上述示例中，我们通过Channel的write方法向通道写入数据，并通过addListener方法注册了一个ChannelFutureListener。
通信传输利器Netty（NetisDotNetty）介绍
通信传输利器Netty（NetisDotNetty）介绍 （先埋怨⼀下微软⼤⼤）我们做NET开发，⼗分羡慕JAVA上能有NETTY, SPRING, STRUTS, DUBBO等等优秀框架，⽽我们NET就只有⼲瞪眼，哎，⽆赖之前⽣态圈没做好，恨铁不成钢啊。
不过由于近来Net Core的发布，慢慢也拉回了⼀⼩部分属于微软的天下，打住，闲话扯到这⼉。
DotNetty是Azure团队仿照（⼏乎可以这么说）JAVA的Netty⽽出来的（⽬前已实现Netty的⼀部分），⽬前在Github上的Star有1.8K+，地址：https:///Azure/DotNetty，没有任何⽂档，和代码中少量的注释。
虽然⽐Netty出来晚了很多年，不过我们NET程序员们也该庆幸了，在⾃⼰的平台上终于能⽤上类似Netty这样强⼤的通信框架了。
传统通讯的问题： 我们使⽤通⽤的应⽤程序或者类库来实现互相通讯，⽐如，我们经常使⽤⼀个 HTTP 客户端库来从 web 服务器上获取信息，或者通过web 服务来执⾏⼀个远程的调⽤。
然⽽，有时候⼀个通⽤的协议或他的实现并没有很好的满⾜需求。
⽐如我们⽆法使⽤⼀个通⽤的 HTTP 服务器来处理⼤⽂件、电⼦邮件以及近实时消息，⽐如⾦融信息和多⼈游戏数据。
我们需要⼀个⾼度优化的协议来处理⼀些特殊的场景。
例如你可能想实现⼀个优化了的Ajax 的聊天应⽤、媒体流传输或者是⼤⽂件传输器，你甚⾄可以⾃⼰设计和实现⼀个全新的协议来准确地实现你的需求。
另⼀个不可避免的情况是当你不得不处理遗留的专有协议来确保与旧系统的互操作性。
在这种情况下，重要的是我们如何才能快速实现协议⽽不牺牲应⽤的稳定性和性能。
解决： Netty 是⼀个提供 asynchronous event-driven （异步事件驱动）的⽹络应⽤框架，是⼀个⽤以快速开发⾼性能、可扩展协议的服务器和客户端。
换句话说，Netty 是⼀个 NIO 客户端服务器框架，使⽤它可以快速简单地开发⽹络应⽤程序，⽐如服务器和客户端的协议。
netty详解（七）netty自定义协议解决TCP粘包和拆包
netty详解（七）netty⾃定义协议解决TCP粘包和拆包⽬录：1、2、3、1、TCP 粘包和拆包基本介绍 TCP 是⾯向连接的，⾯向流的，提供⾼可靠性服务，收发两端（客户端和服务器端）都要⼀⼀成对的 socket。
因此发送端为了将多个发给接收端的包更有效的发给对⽅，使⽤了优化⽅法（Nagle 算法），将多次间隔较⼩且数据量⼩的数据，合并成⼀个⼤的数据块，然后进⾏封包。
这样虽然提⾼了效率，但是接收端就难于分辨出完整的数据包了，因为⾯向流的通信是⽆消息保护边界的。
由TCP ⽆消息保护边界，需要在接收端处理消息边界问题，也就是我们所说的粘包、拆包问题。
2、TCP 粘包和拆包实例演⽰ 在编写 netty 程序时，如果没有做处理，就会发⽣粘包和拆包的问题。
看⼀个具体的实例： Server 端程序package com.oy.tcp;import ty.bootstrap.ServerBootstrap;import ty.channel.ChannelFuture;import ty.channel.ChannelInitializer;import ty.channel.ChannelPipeline;import ty.channel.nio.NioEventLoopGroup;import ty.channel.socket.SocketChannel;import ty.channel.socket.nio.NioServerSocketChannel;public class Server {public static void main(String[] args) {NioEventLoopGroup boss = new NioEventLoopGroup(1);NioEventLoopGroup work = new NioEventLoopGroup();try {ServerBootstrap serverBootstrap = new ServerBootstrap();serverBootstrap.group(boss, work).channel(NioServerSocketChannel.class).childHandler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ChannelPipeline pipeline = ch.pipeline();pipeline.addLast(new MyServerHandler());}});ChannelFuture future = serverBootstrap.bind(8005).sync();System.out.println("server started and listen " + 8005);future.channel().closeFuture().sync();} catch (Exception e) {e.printStackTrace();} finally {boss.shutdownGracefully();work.shutdownGracefully();}}}package com.oy.tcp;import ty.buffer.ByteBuf;import ty.buffer.Unpooled;import ty.channel.ChannelHandlerContext;import ty.channel.SimpleChannelInboundHandler;import ty.util.CharsetUtil;import java.util.UUID;public class MyServerHandler extends SimpleChannelInboundHandler<ByteBuf> {private int count;@Overrideprotected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {//System.out.println("服务器收到的数据：" + msg.toString(CharsetUtil.UTF_8));byte[] buffer = new byte[msg.readableBytes()];msg.readBytes(buffer);// 将 buffer 转成字符串String message = new String(buffer, CharsetUtil.UTF_8);System.out.println("服务器接收数据 " + message);System.out.println("服务器接收到消息量= " + (++this.count));// 服务器会送数据ByteBuf response = Unpooled.copiedBuffer(UUID.randomUUID().toString(), CharsetUtil.UTF_8); ctx.writeAndFlush(response);}@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {ctx.close();}}View Code Client 端程序package com.oy.tcp;import ty.bootstrap.Bootstrap;import ty.channel.ChannelFuture;import ty.channel.ChannelInitializer;import ty.channel.ChannelPipeline;import ty.channel.nio.NioEventLoopGroup;import ty.channel.socket.SocketChannel;import ty.channel.socket.nio.NioSocketChannel;public class Client {public static void main(String[] args) {NioEventLoopGroup group = new NioEventLoopGroup();try {Bootstrap bootstrap = new Bootstrap();bootstrap.group(group).channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ChannelPipeline pipeline = ch.pipeline();pipeline.addLast(new MyClientHandler());}});ChannelFuture future = bootstrap.connect("127.0.0.1", 8005).sync();future.channel().closeFuture().sync();} catch (Exception e) {e.printStackTrace();} finally {group.shutdownGracefully();}}}package com.oy.tcp;import ty.buffer.ByteBuf;import ty.buffer.Unpooled;import ty.channel.ChannelHandlerContext;import ty.channel.SimpleChannelInboundHandler;import ty.util.CharsetUtil;public class MyClientHandler extends SimpleChannelInboundHandler<ByteBuf> {private int count;@Overrideprotected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {byte[] buffer = new byte[msg.readableBytes()];msg.readBytes(buffer);// 将 buffer 转成字符串String message = new String(buffer, CharsetUtil.UTF_8);System.out.println("客户端接收数据 " + message);System.out.println("客户端接收到消息量= " + (++this.count));}@Overridepublic void channelActive(ChannelHandlerContext ctx) throws Exception {// 客户端发送 10 条数据for (int i = 0; i < 10; i++) {ByteBuf buffer = Unpooled.copiedBuffer("hello, server " + i, CharsetUtil.UTF_8);ctx.writeAndFlush(buffer);}}@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {ctx.close();}}View Code3、netty ⾃定义协议解决 TCP 粘包和拆包 使⽤⾃定义协议 + 编解码器来解决。
netty教程
netty教程
Netty 是一个高性能的网络应用框架，适用于开发可扩展的服
务器和客户端。
它提供了一种简单而健壮的异步编程模型，使得开发高性能、高负载的网络应用变得简单和容易。
Netty 的核心思想是基于事件驱动的编程范式，以及基于通道
和处理器的模型。
事件驱动是指程序通过注册感兴趣的事件，并在事件发生时调用相应的处理器来处理事件。
通道是数据的传输载体，处理器是对数据进行处理的逻辑。
Netty 的主要组件包括通道、事件和处理器。
通道是数据在网
络中的传输通道，例如套接字通道。
事件是在通道上发生的状态变化，例如连接被建立或断开。
处理器是对事件进行处理的逻辑单元，例如读取或写入数据。
在使用 Netty 开发网络应用时，首先需要创建一个服务器或客
户端的启动器，并配置相应的参数。
然后，需要注册感兴趣的事件和处理器，以便在事件发生时进行相应的处理。
最后，启动服务器或客户端，并等待事件的发生。
Netty 还提供了丰富的功能和组件，用于简化网络应用的开发。
例如，它提供了各种编解码器，用于处理不同的协议和数据格式。
它还提供了连接池、线程池等功能，用于管理资源和提高性能。
此外，Netty 还支持各种高级功能，如心跳检测、流量
控制、断线重连等。
总结来说，Netty 是一个优秀的网络应用框架，它提供了简单
而强大的编程模型，使得开发高性能、可伸缩的网络应用变得容易。
通过学习 Netty 的教程，你可以掌握使用 Netty 开发网络应用的核心概念和技巧，从而提升你的开发能力。
netty 用法
netty 用法
Netty 是一个基于 Java 的网络应用框架，用于快速、简单地开
发高性能、高可靠性的网络服务器和客户端应用程序。
下面是Netty 的一些主要用法：
1. 异步网络编程：Netty 提供了高度可扩展的异步事件驱动模型，允许并发地处理数千个连接。
通过使用 Netty 的异步编程
模型，可以轻松地编写高效的服务器和客户端应用程序。
2. 高性能的传输：Netty 提供了一组用于传输的抽象，如NIO、Epoll（Linux 2.6+ 版本）、OIO（旧 I/O）等，并通过使用非
阻塞 I/O 操作实现了高性能的数据传输。
3. TCP/UDP 支持：Netty 提供了对 TCP 和 UDP 的支持，开发
者可以轻松地构建各种类型的服务器和客户端应用程序，如HTTP、FTP、DNS、WebSocket 等。
4. 处理器链：Netty 使用处理器链（Pipeline）的概念来处理和
转换网络数据。
每个处理器（Handler）都有其特定的功能，
通过将多个处理器链接在一起，可以构建复杂的网络协议处理逻辑。
5. 简单的线程模型：Netty 提供了简单而灵活的线程模型，可
以根据应用程序的需要配置不同类型的线程池，例如单线程、多线程、线程池等，以实现最佳的性能和资源利用。
6. 即时重连和故障转移：Netty 提供了自动的即时重连和故障
转移机制，使得在网络故障时能够快速地重连，并选择备用服务器进行通信，提高了应用程序的可靠性。
总之，Netty 是一个功能丰富、易用且高性能的网络应用框架，可以满足开发者构建各种类型的服务器和客户端应用程序的需求。
netty 工作原理
netty 工作原理Netty是一种基于Java NIO（非阻塞I/O）的网络编程框架，它的工作原理主要包括以下几个方面：1. Reactor模式：Netty采用了Reactor多线程模型，其中有一个主线程（BossGroup）监听客户端的请求，根据请求的类型分发给工作线程（WorkerGroup）进行处理。
BossGroup和WorkerGroup都是多线程的EventLoopGroup，每个EventLoop都有一个NIO线程，通过selector轮询注册在其上的多个Channel，实现了事件的分发和处理。
2. Channel和Handler：Netty中的Channel表示一个网络连接，它可以注册多个Handler，当有事件发生时，会被对应的Handler进行处理。
Handler负责接收事件，处理事件，并将结果返回给Channel。
3. 编解码器：Netty可以通过添加编解码器来处理不同的协议，例如HTTP、TCP等。
编码器负责将消息转换为数据流，而解码器负责将数据流转换为消息。
4. 异步和非阻塞：Netty利用Java NIO的特性，实现了异步和非阻塞的网络通信。
与传统的阻塞I/O相比，Netty的非阻塞I/O可以支持更多的并发连接，提高了系统的吞吐量和响应速度。
5. Pipeline：在Netty中有一个叫做ChannelPipeline的概念，它是一个事件处理链。
当一个事件在Channel上发生时，会沿着Pipeline流动，依次经过注册的Handler进行处理。
每个Handler都可以根据需要处理事件，或是将事件传递给下一个Handler。
总的来说，Netty通过使用NIO和Reactor模式，实现了基于事件驱动的、高性能的网络编程框架。
它充分利用了异步、非阻塞的特性，提供了简洁易用的API，并支持自定义的编解码器，使得开发者可以轻松地构建高性能的网络应用程序。
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Handler主类:package ty.http.HttpServer;import static ty.handler.codec.http.HttpHeaders.is100ContinueExpected; import static ty.handler.codec.http.HttpHeaders.isKeepAlive;import static s.CONTENT_LENGTH; import static s.COOKIE;import static s.SET_COOKIE; import static ty.handler.codec.http.HttpResponseStatus.CONTINUE;import static ty.handler.codec.http.HttpResponseStatus.OK;import static ty.handler.codec.http.HttpVersion.HTTP_1_1;import java.io.File;import java.io.RandomAccessFile;import java.util.List;import java.util.Map;import java.util.Set;import java.util.Map.Entry;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.FSDataInputStream;import org.apache.hadoop.fs.FileStatus;import org.apache.hadoop.fs.FileSystem;import org.apache.hadoop.fs.Path;import ty.buffer.ChannelBuffer;import ty.channel.ChannelFutureListener;import ty.channel.ChannelHandlerContext;import ty.channel.ExceptionEvent;import ty.channel.MessageEvent;import ty.channel.SimpleChannelUpstreamHandler;import ty.handler.codec.http.Cookie;import ty.handler.codec.http.CookieDecoder;import ty.handler.codec.http.CookieEncoder;import ty.handler.codec.http.DefaultHttpResponse;import ty.handler.codec.http.HttpChunk;import ty.handler.codec.http.HttpChunkTrailer;import ty.handler.codec.http.HttpRequest;import ty.handler.codec.http.HttpResponse;import ty.handler.codec.http.HttpResponseStatus;import ty.handler.codec.http.QueryStringDecoder;import ty.util.CharsetUtil;import ty.http.conf.Conf;public class HttpRequestHandler extends SimpleChannelUpstreamHandler {private HttpRequest request;private boolean readingChunks;private String method = "";private String localpath = "";@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e)throws Exception {e.getCause().printStackTrace();e.getChannel().close();}@Overridepublic void messageReceived(ChannelHandlerContext ctx, MessageEvent e)throws Exception {if (!readingChunks) {HttpRequest request = this.request = (HttpRequest) e.getMessage();String uri = request.getUri();System.out.println("-----------------------------------------------------------------");System.out.println("uri:" + uri);System.out.println("-----------------------------------------------------------------");/**** 100 Continue** 是这样的一种情况：HTTP客户端程序有一个实体的主体部分要发送给服务器，但希望在发送之前查看下服务器是否会** 接受这个实体，所以在发送实体之前先发送了一个携带100** Continue的Expect请求首部的请求。
服务器在收到这样的请求后，应该用100 Continue或一条错误码来进行响应。
*/if (is100ContinueExpected(request)) {send100Continue(e);}// 解析http头部for (Map.Entry<String, String> h : request.getHeaders()) {System.out.println("HEADER: " + h.getKey() + " = "+ h.getValue() + "\r\n");}// 解析请求参数QueryStringDecoder queryStringDecoder = new QueryStringDecoder( request.getUri());Map<String, List<String>> params = queryStringDecoder.getParameters();if (!params.isEmpty()) {for (Entry<String, List<String>> p : params.entrySet()) {String key = p.getKey();List<String> vals = p.getValue();for (String val : vals) {if ("op".equals(key)) {method = val;}if ("localpath".equals(key)) {localpath = val;}System.out.println("PARAM: " + key + " = " + val+ "\r\n");}}}if (request.isChunked()) {readingChunks = true;} else {ChannelBuffer content = request.getContent();if (content.readable()) {System.out.println(content.toString(CharsetUtil.UTF_8));}writeResponse(e, uri);}} else {// 为分块编码时HttpChunk chunk = (HttpChunk) e.getMessage();if (chunk.isLast()) {readingChunks = false;// END OF CONTENT\r\n"HttpChunkTrailer trailer = (HttpChunkTrailer) chunk;if (!trailer.getHeaderNames().isEmpty()) {for (String name : trailer.getHeaderNames()) {for (String value : trailer.getHeaders(name)) {System.out.println("TRAILING HEADER: " + name+ " = " + value + "\r\n");}}}writeResponse(e, "/");} else {System.out.println("CHUNK: "+ chunk.getContent().toString(CharsetUtil.UTF_8)+ "\r\n");}}}private void send100Continue(MessageEvent e) {HttpResponse response = new DefaultHttpResponse(HTTP_1_1, CONTINUE);e.getChannel().write(response);}private void writeResponse(MessageEvent e, String uri) {// 解析Connection首部，判断是否为持久连接boolean keepAlive = isKeepAlive(request);// Build the response object.HttpResponse response = new DefaultHttpResponse(HTTP_1_1, OK);response.setStatus(HttpResponseStatus.OK);// 服务端可以通过location首部将客户端导向某个资源的地址。