前驱知识

WebSocket

维基百科：
WebSocket是一种在单个TCP连接上进行全双工通信的协议。WebSocket通信协议于2011年被IETF定为标准RFC 6455，并由RFC7936补充规范。WebSocket API也被W3C定为标准。

WebSocket使得客户端和服务器之间的数据交换变得更加简单，允许服务端主动向客户端推送数据。在WebSocket API中，浏览器和服务器只需要完成一次握手，两者之间就直接可以创建持久性的连接，并进行双向数据传输。

添加maven依赖

    <build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><configuration><source>8</source><target>8</target></configuration></plugin></plugins></build><dependencies><dependency><groupId>io.netty</groupId><artifactId>netty-all</artifactId><version>4.1.25.Final</version></dependency></dependencies>

编写代码

Chat处理器

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.util.concurrent.GlobalEventExecutor;import java.time.LocalDateTime;/*** @author: Tu9ohost* 处理消息的handler* TextWebSocketFrame: 在netty中，是用于为websocket专门处理文本的对象，frame是消息的载体*/
public class ChatHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {// 用于记录和管理所有客户端的channleprivate static ChannelGroup clients =new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);@Overrideprotected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg)throws Exception {// 获取客户端传输过来的消息String content = msg.text();System.out.println("接受到的数据：" + content);//      for (Channel channel: clients) {
//          channel.writeAndFlush(
//              new TextWebSocketFrame(
//                      "[服务器在]" + LocalDateTime.now()
//                      + "接受到消息, 消息为：" + content));
//      }// 下面这个方法，和上面的for循环，一致clients.writeAndFlush(new TextWebSocketFrame("[服务器在]" + LocalDateTime.now()+ "接受到消息, 消息为：" + content));}/*** 当客户端连接服务端之后（打开连接）* 获取客户端的channle，并且放到ChannelGroup中去进行管理*/@Overridepublic void handlerAdded(ChannelHandlerContext ctx) throws Exception {clients.add(ctx.channel());}@Overridepublic void handlerRemoved(ChannelHandlerContext ctx) throws Exception {// 当触发handlerRemoved，ChannelGroup会自动移除对应客户端的channel
//      clients.remove(ctx.channel());System.out.println("客户端断开，channle对应的长id为："+ ctx.channel().id().asLongText());System.out.println("客户端断开，channle对应的短id为："+ ctx.channel().id().asShortText());}
}

编写服务初始化

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.codec.http.websocketx.WebSocketServerProtocolHandler;
import io.netty.handler.stream.ChunkedWriteHandler;/*** @author: Tu9ohost*/
public class WSServerInitiazer extends ChannelInitializer<SocketChannel> {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ChannelPipeline pipeline = ch.pipeline();// websocket 基于http协议，所以要有http编解码器pipeline.addLast(new HttpServerCodec());// 对写大数据流的支持pipeline.addLast(new ChunkedWriteHandler());// 对httpMessage进行聚合，聚合成FullHttpRequest或FullHttpResponse// 几乎在netty中的编程，都会使用到此hanlerpipeline.addLast(new HttpObjectAggregator(1024*64));// ====================== 以上是用于支持http协议    ======================// ====================== 以下是支持httpWebsocket ======================/*** websocket 服务器处理的协议，用于指定给客户端连接访问的路由 : /ws* 本handler会帮你处理一些繁重的复杂的事* 会帮你处理握手动作： handshaking（close, ping, pong） ping + pong = 心跳* 对于websocket来讲，都是以frames进行传输的，不同的数据类型对应的frames也不同*/pipeline.addLast(new WebSocketServerProtocolHandler("/ws"));// 自定义的handlerpipeline.addLast(new ChatHandler());}
}

主方法

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;/*** @author: Tu9ohost*/
public class WSServer {public static void main(String[] args) throws Exception {EventLoopGroup mainGroup = new NioEventLoopGroup();EventLoopGroup subGroup = new NioEventLoopGroup();try {ServerBootstrap server = new ServerBootstrap();server.group(mainGroup, subGroup).channel(NioServerSocketChannel.class).childHandler(new WSServerInitiazer());// 定义了端口为8088ChannelFuture future = server.bind(8088).sync();future.channel().closeFuture().sync();} finally {mainGroup.shutdownGracefully();subGroup.shutdownGracefully();}}
}

编写界面

<!DOCTYPE html>
<html><head><meta charset="utf-8" /><title></title></head><body><div>发送消息:</div><input type="text" id="msgContent"/><input type="button" value="点我发送" onclick="CHAT.chat()"/><div>接受消息：</div><div id="receiveMsg" style="background-color: gainsboro;"></div><script type="application/javascript">window.CHAT = {socket: null,init: function() {if (window.WebSocket) {CHAT.socket = new WebSocket("ws://127.0.0.1:8088/ws");CHAT.socket.onopen = function() {console.log("连接建立成功...");},CHAT.socket.onclose = function() {console.log("连接关闭...");},CHAT.socket.onerror = function() {console.log("发生错误...");},CHAT.socket.onmessage = function(e) {console.log("接受到消息：" + e.data);var receiveMsg = document.getElementById("receiveMsg");var html = receiveMsg.innerHTML;receiveMsg.innerHTML = html + "<br/>" + e.data;}} else {alert("浏览器不支持websocket协议...");}},chat: function() {var msg = document.getElementById("msgContent");CHAT.socket.send(msg.value);}};CHAT.init();</script></body>
</html>

检验

首先运行主方法，再打开界面，按F12，会显式链接建立成功

随意编写，再点击点我发送

服务端显式

关闭界面窗口，则会显式断开链接id