从BIO到Netty的演变 前言
计算机网络可以说是每个学计算机的都绕不过去的一道坎。计算机网络到底有多么重要，你走到大学图书馆的计算机部分，翻开那些什么《从零开始：黑客XXX》，《黑客攻防从入门到放弃》等书籍，基本第一部分都是在谈论网络。你去一些X客论坛，上面的教程帖也基本都是从网络部分开始的。
相信每一位科班出身的，都学习过《计算机网络》这样书籍， 上过这样的课程。当然教师资源如何，我这里就不谈论，那一定又会引出一顿苦水。但是学习完这样的课程，我们还是对计算机网络感到十分迷茫。这时候的我们可以背下网络七层模型，网络五层模型等，了解局域网，IP等基本地概念，但是计算机网络对于我们来说，还是一个十分空荡荡的名词。
为了更好地了解网络（绝对不是因为那时候很迷黑客的缘故），我决定参加高级网络工程师的考试。通过网络工程师的我对计算机网络有了更为深入的理解，开始将自己的计算机网络体系从概念上勾连起来。也许我可以看懂其中的一些路由规则，甚至看懂一些路由分发的论文。但是我依旧只是站在理论的角度，去理解计算机网络。
到了工作的时候，开始了解Socket编程，开始参与各种实际生产环境的编程。这个时候的我开始对网络有了虽然简单，但是十分真实的接触。计算机网络不再只是停留在书本中的概念，而是我用以实现业务目标的切实手段。
随着工作中开始负责物联网项目的建设，我对网络中的各种协议开始有了自己的认识，甚至可以自己实现网络协议规范的代码落地。于此同时，由于对网络交互的性能要求，我不再只是会使用BIO网络编程，我开始使用NIO网络编程。
为了自己的知识储备，也是为了满足自己的好奇心，我查找了许多的资料，也报了许多课程，去学习网络编程。而我正好周六完成了软考的又一次考试，所以接下来有一定空闲时间的我，接下来会继续整理我的知识，并将它写成博客。
这篇博客的主要内容就是按照演变的顺序，写下BIO->NIO->Reactor->Netty这样的四个里程碑。这也是大佬们推荐的计算机网络编程的学习路线。不过这次只是给个整体的认识以及demo，更为深入的原理探究，会放在后面。
BIO 介绍几乎每个人都是BIO开始的计算机网络编程，而其中大部分也永远地留在了这个计算机网络编程的模型。
优点理解简单
实现简单
要求较低
缺点性能低
瓶颈低
扩展难
代码示例（BIO下TCP）这里给出一些简单的demo，供大家认识。
BIO_Client package tech.jarry.learning.netease; import java.io.IOException; import java.io.OutputStream; import java.net.Inet4Address; import java.net.InetSocketAddress; import java.net.Socket; import java.nio.charset.Charset; import java.util.Scanner; /** * @Description： * @Author: jarry */ public class BIOClient { private static final Charset charset = Charset.forName("utf-8"); public static void main(String[] args) throws IOException { Socket socket = new Socket(); // Socket socket = new Socket("localhost", 8080); // 我还以为可以的。但是貌似上面的8080表示目标端口，而下面的8080表示源端口（发送端口） // socket.bind(new InetSocketAddress("localhost", 8080)); // 后来才去确定，.bind是用于绑定源信息，而.connect是用于绑定目标信息 socket.connect(new InetSocketAddress(Inet4Address.getLocalHost(), 8080)); OutputStream outputStream = socket.getOutputStream(); Scanner scanner = new Scanner(System.in); System.out.println("please input: "); String msg = scanner.nextLine(); outputStream.write(msg.getBytes(charset)); scanner.close(); outputStream.close(); socket.close(); } } BIO_ServerV1 package tech.jarry.learning.netease; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.net.InetSocketAddress; import java.net.ServerSocket; import java.net.Socket; /** * @Description： BIO模型中Server端的简单实现 * @Author: jarry */ public class BIOServer { public static void main(String[] args) throws IOException { ServerSocket serverSocket = new ServerSocket(); serverSocket.bind(new InetSocketAddress(8080)); System.out.println("server has started"); while (!serverSocket.isClosed()) { Socket requestClient = serverSocket.accept(); System.out.println("server get a connection: " + requestClient.toString()); InputStream requestInputStream = requestClient.getInputStream(); BufferedReader reader = new BufferedReader(new InputStreamReader(requestInputStream)); String msg; while ((msg = reader.readLine()) != null) { if (msg.length() == 0) { break; } System.out.println(msg); } System.out.println("server has receive a message from: " + requestClient.toString()); requestInputStream.close(); requestClient.close(); } serverSocket.close(); } } BIO_ServerV2 package tech.jarry.learning.netease; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.net.InetSocketAddress; import java.net.ServerSocket; import java.net.Socket; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; /** * @Description： 直接对原有代码BIOServer进行暴力修改，将其阻塞部分，通过多线程实现异步处理 * @Author: jarry */ public class BIOServer1 { private static ExecutorService executorService = Executors.newCachedThreadPool(); public static void main(String[] args) throws IOException { ServerSocket serverSocket = new ServerSocket(); serverSocket.bind(new InetSocketAddress(8080)); System.out.println("server has started"); while (!serverSocket.isClosed()) { Socket requestClient = serverSocket.accept(); System.out.println("server get a connection: " + requestClient.toString()); executorService.submit(new Runnable() { @Override public void run() { InputStream requestInputStream = null; try { requestInputStream = requestClient.getInputStream(); } catch (IOException e) { e.printStackTrace(); } BufferedReader reader = new BufferedReader(new InputStreamReader(requestInputStream)); String msg = null; while (true) { try { if (!((msg = reader.readLine()) != null)) { break; } } catch (IOException e) { e.printStackTrace(); } if (msg.length() == 0) { break; } System.out.println(msg); } System.out.println("server has receive a message from: " + requestClient.toString()); try { requestInputStream.close(); requestClient.close(); } catch (IOException e) { e.printStackTrace(); } } }); } serverSocket.close(); } /** * 运行结果分析： * server has started * server get a connection: Socket[addr=http://www.likecs.com/10.0.75.1,port=64042,localport=8080] * server get a connection: Socket[addr=http://www.likecs.com/10.0.75.1,port=64052,localport=8080] * server get a connection: Socket[addr=http://www.likecs.com/10.0.75.1,port=64061,localport=8080] * 123 * server has receive a message from: Socket[addr=http://www.likecs.com/10.0.75.1,port=64042,localport=8080] * 456 * server has receive a message from: Socket[addr=http://www.likecs.com/10.0.75.1,port=64052,localport=8080] * 789 * server has receive a message from: Socket[addr=http://www.likecs.com/10.0.75.1,port=64061,localport=8080] */ } BIO_ServerV3 package tech.jarry.learning.netease; import java.io.*; import java.net.InetSocketAddress; import java.net.ServerSocket; import java.net.Socket; /** * @Description： 直接对原有代码BIOServer进行暴力修改，增加了其http格式的返回，确保浏览器可以正常访问 * @Author: jarry */ public class BIOServer2 { public static void main(String[] args) throws IOException { ServerSocket serverSocket = new ServerSocket(); serverSocket.bind(new InetSocketAddress(8080)); System.out.println("server has started"); while (!serverSocket.isClosed()) { Socket requestClient = serverSocket.accept(); System.out.println("server get a connection: " + requestClient.toString()); InputStream requestInputStream = requestClient.getInputStream(); BufferedReader reader = new BufferedReader(new InputStreamReader(requestInputStream)); String msg; while ((msg = reader.readLine()) != null) { if (msg.length() == 0) { break; } System.out.println(msg); } System.out.println("server has receive a message from: " + requestClient.toString()); // 返回数据，并确保可以被http协议理解 OutputStream outputStream = requestClient.getOutputStream(); outputStream.write("HTTP/1.1 200 OK\r\r".getBytes("utf-8")); outputStream.write("Content-Length: 11\r\n\r\n".getBytes("utf-8")); outputStream.write("Hello World".getBytes("utf-8")); outputStream.flush(); requestInputStream.close(); outputStream.close(); requestClient.close(); } serverSocket.close(); } /** * 运行结果分析： */ // server has started // server get a connection: Socket[addr=http://www.likecs.com/0:0:0:0:0:0:0:1,port=63008,localport=8080] // GET / HTTP/1.1 // Host: localhost:8080 // Connection: keep-alive // Cache-Control: max-age=0 // Upgrade-Insecure-Requests: 1 // User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77.0.3865.90 Safari/537.36 // Sec-Fetch-Mode: navigate // Sec-Fetch-User: ?1 // Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3 // Sec-Fetch-Site: none // Accept-Encoding: gzip, deflate, br // Accept-Language: en-US,en;q=0.9,zh-CN;q=0.8,zh;q=0.7 // Cookie: Webstorm-c7a2b5a2=b5e53f87-54cc-41d5-a21f-c7be3056dfe8; centcontrol_login_token=09E8A6B6888CB0B7A9F89AB3DB5FAFE4 // server has receive a message from: Socket[addr=http://www.likecs.com/0:0:0:0:0:0:0:1,port=63008,localport=8080] // server get a connection: Socket[addr=http://www.likecs.com/0:0:0:0:0:0:0:1,port=63009,localport=8080] // GET /favicon.ico HTTP/1.1 // Host: localhost:8080 // Connection: keep-alive // Pragma: no-cache // Cache-Control: no-cache // Sec-Fetch-Mode: no-cors // User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77.0.3865.90 Safari/537.36 // Accept: image/webp,image/apng,image/*,*/*;q=0.8 // Sec-Fetch-Site: same-origin // Referer: :8080/ // Accept-Encoding: gzip, deflate, br // Accept-Language: en-US,en;q=0.9,zh-CN;q=0.8,zh;q=0.7 // Cookie: Webstorm-c7a2b5a2=b5e53f87-54cc-41d5-a21f-c7be3056dfe8; centcontrol_login_token=09E8A6B6888CB0B7A9F89AB3DB5FAFE4 // server has receive a message from: Socket[addr=http://www.likecs.com/0:0:0:0:0:0:0:1,port=63009,localport=8080] }上面的代码是一套的，可以进行Server与Client的通信，功能较为简单。