一、微信小程序實現WebSocket客戶端程序

1. 界面實現

<input name="url" value="{{url}}" bindinput ="urlInput"/>
<button size='mini' type="warn">斷開連接</button>
<button size='mini' type="primary" bindtap="connectSocket">開啟連接</button>
<textarea placeholder="輸入發送內容" bindinput ="msgInput"></textarea>
<button size='mini' type="primary" bindtap="sendMsg">發送</button>
<view wx:for="{{msgs}}">{{index}}: {{item}}</view>

界面效果：

2. WXS部分

Page({
  data: {
    url: 'ws://localhost:8888/ws',
    msgs: [],
    msg: '',
  }
  // 連接WebSocket服務  
  connectSocket() {    
    let _this = this;    
    // 連接websocket服務    
    let task = wx.connectSocket({      
      url: _this.data.url    
    });    
    // 監聽websocket消息，并將接收到的消息添加到消息數組msgs中   
    task.onMessage(function(res) {       
      _this.setData({        
        msgs: [..._this.data.msgs, "接收到消息 -> " + res.data]      
      });    
    });    
    // 保存websocket實例     
    _this.setData({       
      socketTask: task,       
      msgs: [..._this.data.msgs,"連接成功!"]    
    });  
  },    
  
  // 獲取輸入內容，并臨時保存在msg中  
  msgInput(e) {    
    this.setData({       
      msg: e.detail.value    
    });  
  },    
  
  // 發送消息  
  sendMsg() {    
    // 1.獲取輸入內容    
    let msg = this.data.msg;    
    // 2.發送消息到WebSocket服務端    
    this.data.socketTask.send({      
      data: msg    
    });  
  }
})

二、Netty實現WebSocket服務端程序

1. 新建一個Maven工程，并引入Netty依賴

• 項目目錄結構：

• 引入Netty依賴：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>io.netty</groupId>
    <artifactId>NettyWebSocket</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-all</artifactId>
            <version>4.1.48.Final</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

2. 自定義處理器

• 定義一個專門處理Http協議的處理器，當瀏覽器第一次連接時候會讀取首頁的html文件，并將html文件內容返回給瀏覽器展示。

package io.netty.websocket;

import io.netty.channel.*;
import io.netty.handler.codec.http.*;
import io.netty.handler.ssl.SslHandler;
import io.netty.handler.stream.ChunkedNioFile;

import java.io.File;
import java.io.RandomAccessFile;
import java.net.URISyntaxException;
import java.net.URL;

// 處理Http協議的Handler，該Handler只會在第一次客戶端連接時候有用。
public class HttpRequestHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
    private final String wsUri;
    private static final File INDEX;

    static {
        URL location = HttpRequestHandler.class.getProtectionDomain()
                .getCodeSource().getLocation();
        try {
            String path = location.toURI() + "index.html";
            path = !path.contains("file:") ? path : path.substring(5);
            INDEX = new File(path);
        } catch (URISyntaxException e) {
            throw new IllegalStateException("Unable to locate index.html", e);
        }
    }

    public HttpRequestHandler(String wsUri) {
        this.wsUri = wsUri;
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
        // 如果被請求的 URL 以/ws 結尾，那么我們將會把該協議升級為 WebSocket。
        if (wsUri.equalsIgnoreCase(request.getUri())) {
            // 將請求傳遞給下一個ChannelHandler，即WebSocketServerProtocolHandler處理
            // request.retain()會增加引用計數器，以防止資源被釋放
            ctx.fireChannelRead(request.retain());
            return;
        }
        handleHttpRequest(ctx, request);
    }

    /**
     * 該方法讀取首頁html文件內容，然后將內容返回給客戶端展示
     * @param ctx
     * @param request
     * @throws Exception
     */
    private void handleHttpRequest(ChannelHandlerContext ctx, FullHttpRequest request) throws Exception {
        // HTTP1.1協議允許客戶端先判定服務器是否愿意接受客戶端發來的消息主體，以減少由于服務器拒絕請求所帶來的額外資源開銷
        if (HttpHeaders.is100ContinueExpected(request)) {
            FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.CONTINUE);
            ctx.writeAndFlush(response);
        }
        // 從resources目錄讀取index.html文件
        RandomAccessFile file = new RandomAccessFile(INDEX, "r");
        // 準備響應頭信息
        HttpResponse response = new DefaultHttpResponse(request.getProtocolVersion(), HttpResponseStatus.OK);
        response.headers().set(HttpHeaders.Names.CONTENT_TYPE, "text/html; charset=UTF-8");
        boolean keepAlive = HttpHeaders.isKeepAlive(request);
        if (keepAlive) {
            response.headers().set(HttpHeaders.Names.CONTENT_LENGTH, file.length());
            response.headers().set(HttpHeaders.Names.CONNECTION, HttpHeaders.Values.KEEP_ALIVE);
        }
        ctx.write(response);
        // 輸出html文件內容
        ctx.write(new ChunkedNioFile(file.getChannel()));
        // 最后發送一個LastHttpContent來標記響應的結束
        ChannelFuture future = ctx.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT);
        // 如果不是長鏈接，則在寫操作完成后關閉Channel
        if (!keepAlive) {
            future.addListener(ChannelFutureListener.CLOSE);
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
            throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}

• 定義一個專門處理WebSocket協議的處理器。

package io.netty.websocket;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.group.ChannelGroup;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketServerProtocolHandler;

// 處理WebSocket協議的Handler
public class TextWebSocketFrameHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {
    private final ChannelGroup channelGroup;

    public TextWebSocketFrameHandler(ChannelGroup channelGroup) {
        this.channelGroup = channelGroup;
    }

    // 用戶事件監聽，每次客戶端連接時候自動觸發
    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        String content = "Client " + ctx.channel().remoteAddress().toString().substring(1) + " joined";
        System.out.println(content);
        // 如果是握手完成事件，則從Pipeline中刪除HttpRequestHandler，并將當前channel添加到ChannelGroup中
        if (evt == WebSocketServerProtocolHandler.ServerHandshakeStateEvent.HANDSHAKE_COMPLETE) {
            // 從Pipeline中刪除HttpRequestHandler
            ctx.pipeline().remove(HttpRequestHandler.class);
            // 通知所有已連接的WebSocket客戶端，新的客戶端已經連接上了
            TextWebSocketFrame msg = new TextWebSocketFrame(content);
            channelGroup.writeAndFlush(msg);
            // 將WebSocket Channel添加到ChannelGroup中，以便可以它接收所有消息
            channelGroup.add(ctx.channel());
        } else {
            super.userEventTriggered(ctx, evt);
        }
    }

    // 每次客戶端發送消息時執行
    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, TextWebSocketFrame msg) throws Exception {
        System.out.println("讀取到的消息：" + msg.retain());
        // 將讀取到的消息寫到ChannelGroup中所有已經連接的客戶端
        channelGroup.writeAndFlush(msg.retain());
    }
}

上面userEventTriggered方法監聽用戶事件。當有客戶端連接時候，會自動執行該方法。而channelRead0方法負責讀取客戶端發送過來的消息，然后通過channelGroup將消息輸出到所有已連接的客戶端。

3. 定義初始化器

定義一個ChannelInitializer的子類，其主要目的是在某個 Channel 注冊到 EventLoop 后，對這個 Channel 執行一些初始化操作。

package io.netty.websocket;

import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.group.ChannelGroup;
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;

public class ChatServerInitializer extends ChannelInitializer<Channel> {
    private final ChannelGroup channelGroup;

    public ChatServerInitializer(ChannelGroup channelGroup) {
        this.channelGroup = channelGroup;
    }

    @Override
    protected void initChannel(Channel channel) throws Exception {
        ChannelPipeline pipeline = channel.pipeline();
        // 安裝編解碼器，以實現對HttpRequest、 HttpContent、LastHttp-Content與字節之間的編解碼
        pipeline.addLast(new HttpServerCodec());
        // 專門處理寫文件的Handler
        pipeline.addLast(new ChunkedWriteHandler());
        // Http聚合器，可以讓pipeline中下一個Channel收到完整的HTTP信息
        pipeline.addLast(new HttpObjectAggregator(64 * 1024));
        // 處理Http協議的ChannelHandler，只會在客戶端第一次連接時候有用
        pipeline.addLast(new HttpRequestHandler("/ws"));
        // 升級Websocket后，使用該 ChannelHandler 處理Websocket請求
        pipeline.addLast(new WebSocketServerProtocolHandler("/ws"));
        // 安裝專門處理 Websocket TextWebSocketFrame 幀的處理器
        pipeline.addLast(new TextWebSocketFrameHandler(channelGroup));
    }
}

4. 創建啟動類

package io.netty.websocket;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.util.concurrent.ImmediateEventExecutor;

import java.net.InetSocketAddress;

public class ChatServer {

    public void start() {
        ChannelGroup channelGroup = new DefaultChannelGroup(ImmediateEventExecutor.INSTANCE);
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChatServerInitializer(channelGroup));
            ChannelFuture future = bootstrap.bind(new InetSocketAddress(8888)).syncUninterruptibly();
            System.out.println("Starting ChatServer on port 8888 ...");
            future.channel().closeFuture().syncUninterruptibly();
        } finally {
            channelGroup.close();
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        new ChatServer().start();
    }
}

5. 編寫一個html文件

該html文件提供網頁版的WebSocket客戶端頁面。在src/main/resources目錄下新建一個html文件。

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>WebSocket Chat</title>
</head>
<body>
<form οnsubmit="return false;">
    <h3>WebSocket 聊天室：</h3>
    <textarea id="responseText" style="width: 500px; height: 300px;"></textarea><br/>
    <input type="text" name="message"  style="width: 300px" value="Hello Netty"/>
    <input type="button" value="發送消息" onclick="send(this.form.message.value)"/>
    <input type="button" value="清空聊天記錄" onclick="clearScreen()"/>
</form>
<script type="text/javascript">
    var socket;
    if (!window.WebSocket) {
        window.WebSocket = window.MozWebSocket;
    }
    if (window.WebSocket) {
        socket = new WebSocket("ws://localhost:8888/ws");
        // 注意：使用tls協議通信時候，協議名為wss
        // socket = new WebSocket("wss://localhost:8443/ws");
        socket.onopen = function(event) {
            var ta = document.getElementById('responseText');
            ta.value = "連接開啟!";
        };
        socket.onclose = function(event) {
            var ta = document.getElementById('responseText');
            ta.value = ta.value + '\n' + "連接被關閉!";
        };
        socket.onmessage = function(event) {
            var ta = document.getElementById('responseText');
            ta.value = ta.value + '\n' + event.data;
        };
    } else {
        alert("你的瀏覽器不支持 WebSocket!");
    }

    function send(message) {
        if (!window.WebSocket) {
            return;
        }
        if (socket.readyState == WebSocket.OPEN) {
            socket.send(message);
        } else {
            alert("連接沒有開啟.");
        }
    }

    function clearScreen() {
        document.getElementById('responseText').value = "";
    }
</script>
</body>
</html>

界面效果：

最終效果：