It’s time to teach everyone how to write code, even though no one is watching…

This is the second part of the distributed Systems Hands-on series. Why is this series written? And what was canto I?

Cow force! Implement a distributed RPC framework from 0 by myself, and successfully win the offer from Ali!

These projects are I spent a lot of day and night out of the masturbation, but the reading volume is not high, as expected, hardcore technology text we do not like to see.

But that’s okay, I’m going to stick with it, because it’s valuable and it’s something that really adds value to your resume.

Read carefully and follow me to achieve the partners, I believe you will have a harvest.

Github address: (welcome star)

Github.com/xiajunhust/…

The advantage of websocket

HTTP vs. Websocket

Common application scenarios of WebSocket:

• Real-time Web applications. Display real-time data on the server on the client. Such as trading site price information.
• Game applications.
• Chat apps.

The life cycle of webSocket connections

The full life cycle of a Websocket connection can be represented as follows:

To establish a Websocket connection between the client and server, the client sends an HTTP handshake request:

GET /chat HTTP/1.1

Host: server.example.com

Upgrade: websocket

Connection: Upgrade

Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==

Origin: example.com\ Sec-WebSocket-Protocol: chat, superchat

Sec-WebSocket-Version: 13

Opcode is used to identify the type of frame:

Websocket server can accept the connection of multiple clients and provide services.

netty server:

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; import io.netty.handler.codec.http.*; import io.netty.handler.stream.ChunkedWriteHandler; import lombok.extern.slf4j.Slf4j; /** * websocket server based netty * * @author summer * @version $Id: SimpleWebsocketServer.java, V 0.1 2022年01月26日 9:34 AM Summer Exp $*/ @slf4j public class SimpleWebsocketServer {/** * host */ public final static String host = "127.0.0.1"; /** * port number */ public final static Integer port = 8085; /** * Netty server start method */ public void start() {log.info("SimpleWebsocketServer start begin "); EventLoopGroup bossEventLoopGroup = new NioEventLoopGroup(1); EventLoopGroup workerEventLoopGroup = new NioEventLoopGroup(); try { ServerBootstrap serverBootstrap = new ServerBootstrap() .group(bossEventLoopGroup, WorkerEventLoopGroup). Channel (NioServerSocketChannel. Class) / / open TCP nagle algorithm. ChildOption (ChannelOption TCP_NODELAY, True) // Enable the long connection. ChildOption (channeloption.so_keepalive, true) .childHandler(new ChannelInitializer<SocketChannel>() { @Override protected void initChannel(SocketChannel c) { c.pipeline().addLast(new HttpServerCodec()) .addLast(new HttpObjectAggregator(512 * 1024)) .addLast(new ChunkedWriteHandler()) .addLast(new SimpleWebsocketServerHandler()); }}); ChannelFuture channelFuture = serverBootstrap.bind(host, port).sync(); log.info("SimpleWebsocketServer start at port " + port); channelFuture.channel().closeFuture().sync(); } catch (Exception e) { log.error("SimpleWebsocketServer start exception,", e); } finally { log.info("SimpleWebsocketServer shutdown bossEventLoopGroup&workerEventLoopGroup gracefully"); bossEventLoopGroup.shutdownGracefully(); workerEventLoopGroup.shutdownGracefully(); }}}Copy the code

The actual HTTP request handler:

import com.alibaba.fastjson.JSON; import io.netty.buffer.Unpooled; import io.netty.channel.ChannelFutureListener; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.SimpleChannelInboundHandler; import io.netty.handler.codec.http.*; import io.netty.handler.codec.http.websocketx.*; import lombok.extern.slf4j.Slf4j; import org.apache.commons.lang3.StringUtils; import java.nio.charset.StandardCharsets; import java.util.List; import java.util.Map; ** @author summer * @version $Id: SimpleWebsocketServerHandler.java, January 26, 2022 v 0.1 9:44 AM summer Exp $* / @ Slf4j public class SimpleWebsocketServerHandler extends SimpleChannelInboundHandler<Object> { /** *websocket shake handler */ private WebSocketServerHandshaker handshaker; @Override protected void channelRead0(ChannelHandlerContext ctx, Object msg) { try { log.info("SimpleWebsocketServerHandler receive msg=" + msg); if (msg instanceof FullHttpRequest) { handleHttpShakehandRequest(ctx, (FullHttpRequest)msg); } else if (msg instanceof WebSocketFrame) { handleWebsocketFrame(ctx, (WebSocketFrame)msg); } else { log.error("SimpleWebsocketServerHandler channelRead0,unkown msg"); } } catch (Exception e) { log.error("channelRead0 exception,", e); }} /** * handle the handshake request ** @param CTX * @param fullHttpRequest */ private void handleHttpShakehandRequest(ChannelHandlerContext ctx, FullHttpRequest fullHttpRequest) { log.info("handleHttpShakehandRequest begin~"); // Check HTTP header validity if (! fullHttpRequest.getDecoderResult().isSuccess() || ! StringUtils.equals("websocket", fullHttpRequest.headers().get("Upgrade"))) { log.warn("handleHttpShakehandRequest fail,fullHttpRequest illegal,fullHttpRequest=" + fullHttpRequest.toString()); return; } / / construct a handshake response returned String webSocketURL = SimpleWebsocketServer. Host + ":" + SimpleWebsocketServer. Port + "/ websocket"; WebSocketServerHandshakerFactory factory = new WebSocketServerHandshakerFactory(webSocketURL, null, false); Handshaker = factory.newhandshaker (fullHttpRequest); if (handshaker == null) { log.warn("handleHttpShakehandRequest fail,sendUnsupportedVersionResponse,fullHttpRequest=" + fullHttpRequest.toString()); / / does not support WebSocketServerHandshakerFactory. SendUnsupportedVersionResponse (CTX) channel ()); } else { log.info("handleHttpShakehandRequest success."); handshaker.handshake(ctx.channel(), fullHttpRequest); Private void handleWebsocketFrame(ChannelHandlerContext CTX, WebSocketFrame webSocketFrame) { if (webSocketFrame instanceof CloseWebSocketFrame) { log.info("handleWebsocketFrame close frame"); // Control frames - close handshaker.close(ctx.channel(), (CloseWebSocketFrame)webSocketFrame.retain()); return; } if (webSocketFrame instanceof PingWebSocketFrame) { log.info("handleWebsocketFrame ping frame"); -ping ctx.channel().write(new PongWebSocketFrame(webSocketframe.content ().retain())); return; } // Data frame, support text only if (! (webSocketFrame instanceof TextWebSocketFrame)) { log.error("handleWebsocketFrame,unsupprted data frame"); return; } TextWebSocketFrame textWebSocketFrame = (TextWebSocketFrame)webSocketFrame; String Request = textWebSocketFrame.text(); log.info("handleWebsocketFrame,receive data frame,text=" + request); ctx.channel().write(new TextWebSocketFrame(request + "_" + System.currentTimeMillis())); } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { log.error("SimpleWebsocketServerHandler exception,", cause); ctx.close(); } @Override public void channelReadComplete(ChannelHandlerContext ctx) { ctx.flush(); }}Copy the code

Start netty Server in springBoot main program:

import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication public class SimplewebsocketserverApplication { public static void main(String[] args) { SimpleWebsocketServer simpleWebsocketServer = new SimpleWebsocketServer(); simpleWebsocketServer.start(); SpringApplication.run(SimplewebsocketserverApplication.class, args); }}Copy the code

<! DOCTYPE HTML > < HTML > <head> <meta charset=" utF-8 "> <title>websocket </title> <style type="text/ CSS "> h3,h4{ text-align:center; </style> </head> <body> <h3> <span style="color:red"> console </span> </h3> <h4> Single message <li>url=/ API /ws/sendOne? Message = Single message content &id=none</li> Group message <li>url=/ API /ws/sendAll? </li> </h4> <script type="text/javascript"> var socket; If (typeof (WebSocket) == "undefined") {console.log(" Sorry: your browser does not support WebSocket"); } else {console.log(" Congratulations: your browser supports WebSocket"); // Set up a connection with the port. // Note that WS and WSS use different ports. WSS can not be used, the browser opened WebSocket error //ws corresponds to HTTP, WSS corresponds to HTTPS. socket = new WebSocket("ws://localhost:8085/ws/asset"); Onopen = function() {console.log("Socket open "); Socket. send(" Message sending test (From Client)"); }; Onmessage = function(MSG) {console.log(MSG); // get server push alert(msg.data) //console.log(msg.data); }; Onclose = function() {console.log(" socket closed "); }; Onerror = function() {alert(" socket error "); } // Close connection window.unload=function() {socket.close(); }; } </script> </body> </html>Copy the code

The server logs are displayed normally:

[nioEventLoopGroup 23:52:26. 559-3-1] INFO com. Summer. Simplewebsocketserver. SimpleWebsocketServerHandler - SimpleWebsocketServerHandler receive msg=HttpObjectAggregator$AggregatedFullHttpRequest(decodeResult: success, version: HTTP/1.1, Content: CompositeByteBuf(Ridx: 0, widx: 0, CAP: 0, Components =0)) GET /ws/asset Localhost :8085 Connection: Upgrade Pragma: no-cache cache-control: no-cache user-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36 Upgrade: websocket Origin: null Sec-WebSocket-Version: 13 Accept-Encoding: gzip, deflate, br Accept-Language: zh-CN,zh; Q = 0.9, en. Q= 0.8 sec-websocket-key: 2qmtoAbFKDi3nccZdLJrzQ== sec-websocket-extensions: permessage-deflate; client_max_window_bits content-length: 0 23:52:26. [559] nioEventLoopGroup - 3-1 the INFO com. Summer. Simplewebsocketserver. SimpleWebsocketServerHandler - [nioEventLoopGroup handleHttpShakehandRequest begin ~ 23:52:26. 563-3-1] INFO Com. Summer. Simplewebsocketserver. SimpleWebsocketServerHandler - handleHttpShakehandRequest success. 23:52:26. 574 [nioEventLoopGroup-3-1] DEBUG io.netty.handler.codec.http.websocketx.WebSocketServerHandshaker - [id: 0x0f7a984c, L:/127.0.0.1:8085 -r :/127.0.0.1:50041] WebSocket Version V13 Server Handshake 23:52:26.576 [nioEventLoopgroup-3-1] DEBUG io.netty.handler.codec.http.websocketx.WebSocketServerHandshaker - WebSocket version 13 server handshake key: 2qmtoAbFKDi3nccZdLJrzQ==, response: [nioEventLoopGroup XQR0ok8e59cI934NeuY5LCbiVXY = 23:52:26. 645-3-1] INFO com.summer.simplewebsocketserver.SimpleWebsocketServerHandler - SimpleWebsocketServerHandler receive msg=TextWebSocketFrame(data: PooledUnsafeDirectByteBuf(ridx: 0, widx: 31, cap: 31)) 23:52:26. [646] nioEventLoopGroup - 3-1 the INFO com. Summer. Simplewebsocketserver. SimpleWebsocketServerHandler - HandleWebsocketFrame, receive the data frame, the text message sending = test (From the Client) 23:52:26. 648] [nioEventLoopGroup - 3-1 the INFO com.summer.simplewebsocketserver.SimpleWebsocketServerHandler - handleWebsocketFrame,send response text Success :[This is the response result [message send test (From Client)]_1643471546646Copy the code

This article took me quite a long time to write out, look at these detailed code implementation, you should feel I want to teach you sincerity ~~~

If you feel useful, click “like” + “share” + “favorites”, one button three links to prevent lost wow ~