netty websocket

WebSocketServer

package com.zhaowb.netty.ch11;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
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.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.stream.ChunkedWriteHandler;

public class WebSocketServer {

    public void run(int port) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ChannelPipeline pipeline = ch.pipeline();
                    pipeline.addLast("http-codec", new HttpServerCodec());// 添加 HttpServerCodec 将请求和应答消息编码或解码为HTTP 消息
                    pipeline.addLast("aggregator", new HttpObjectAggregator(65536)); // 增加HttpObjectAggregator ，将HTTP 消息的多个部分组合成一条完整的HTTP消息
                    pipeline.addLast("http-chunked", new ChunkedWriteHandler());// 添加ChunkedWriteHandler，来向客户端发送HTML5文件，主要用于支持浏览器和服务端进行WebSocket 通信。
                    pipeline.addLast("handle", new WebSocketServerHandler()); // 增加WebSocket 服务端的handler
                }
            });
            Channel ch = b.bind(port).sync().channel();

            System.out.println("Web socket server started at port : " + port + '.');
            System.out.println("Open your browser and navigate to http://localhost:" + port + '/');
            ch.closeFuture().sync();
        } catch (Exception e) {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {

        int port = 8080;
        if (args.length > 0) {
            try {
                port = Integer.parseInt(args[0]);
            } catch (NumberFormatException e) {
                e.printStackTrace();
            }
        }
        new WebSocketServer().run(port);

    }
}

WebSocketServerHandler

package com.zhaowb.netty.ch11;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.*;
import io.netty.handler.codec.http.*;
import io.netty.handler.codec.http.websocketx.*;
import io.netty.util.CharsetUtil;

import java.util.Date;
import java.util.logging.Level;
import java.util.logging.Logger;

import static io.netty.handler.codec.http.HttpHeaders.isKeepAlive;
import static io.netty.handler.codec.http.HttpHeaders.setContentLength;
import static io.netty.handler.codec.http.HttpResponseStatus.BAD_REQUEST;

public class WebSocketServerHandler extends SimpleChannelInboundHandler<Object> {

    private static final Logger logger = Logger.getLogger(WebSocketServerHandler.class.getName());

    private WebSocketServerHandshaker handshaker;

    /**
     * 第一次握手请求消息由HTTP协议承载，所有它是一个HTTP 消息，执行handleHttpRequest方法来处理WebSocket 握手请求。
     *
     * @param ctx
     * @param msg
     * @throws Exception
     */
    @Override
    protected void messageReceived(ChannelHandlerContext ctx, Object msg) throws Exception {
        // 传统HTTP 接入
        if (msg instanceof FullHttpRequest) {
            handleHttpRequest(ctx, (FullHttpRequest) msg);
        } else if (msg instanceof WebSocketFrame) {
            handleWebSocketFrame(ctx, (WebSocketFrame) msg);
        }
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        ctx.flush();
    }

    private void handleHttpRequest(ChannelHandlerContext ctx, FullHttpRequest req) {

        /**
         * 对握手请求消息进行判断，如果消息头中没有包含Upgrade 字段或者它的值不是websocket。则返回HTTP 400响应
         */
        // 如果HTTP解码失败，返回HTTP异常
        if (!req.getDecoderResult().isSuccess() || (!"websocket".equals(req.headers().get("Upgrade")))) {
            sendHttpResponse(ctx, req, new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, BAD_REQUEST));
            return;
        }

        // 构造握手响应返回，本机测试。
        /**
         * 握手请求简单校验通过之后，开始构造握手工厂，创建握手处理类 WebSocketServerHandshaker，通过它构造握手响应消息
         * 返回给客户端，同时将WebSocket相关的编码和解码类动态添加到ChannelPipeline中，用于WebSocket消息的编解码
         */
        WebSocketServerHandshakerFactory wsFactory = new WebSocketServerHandshakerFactory("ws:localhost:8080/websocket", null, false);
        handshaker = wsFactory.newHandshaker(req);
        if (handshaker == null) {
            WebSocketServerHandshakerFactory.sendUnsupportedWebSocketVersionResponse(ctx.channel());
        } else {
            handshaker.handshake(ctx.channel(), req);
        }
    }

    /**
     * 对WebSocket 请求消息进行处理，首先需要对控制帧进行判断，如果是关闭链路的控制信息，就调用WebSocketServerHandshaker
     * 的close 方法关闭WebSocket连接，如果是维持链路的Ping消息，则构造Pong消息返回。
     * @param ctx
     * @param frame
     */
    private void handleWebSocketFrame(ChannelHandlerContext ctx, WebSocketFrame frame) {
        // 判断链路是否关闭
        if (frame instanceof CloseWebSocketFrame) {
            handshaker.close(ctx.channel(), (CloseWebSocketFrame) frame.retain());
            return;
        }
        // 支持文本信息，不支持二进制
        if (!(frame instanceof TextWebSocketFrame)) {
            throw new UnsupportedOperationException(String.format("%s frame types not supported", frame.getClass().getName()));
        }
        // 返回应答消息
        // 从TextWebSocketFrame中获取请求消息字符串，对它处理通过后构造新的TextWebSocketFrame消息，返回给客户端，
        // 由于握手应答时动态增加了TextWebSocketFrame的编码类，所以直接发送TextWebSocketFrame对象。
        String request = ((TextWebSocketFrame) frame).text();
        if (logger.isLoggable(Level.FINE)) {
            logger.fine(String.format("%s received %s", ctx.channel()));
        }
        ctx.channel().write(new TextWebSocketFrame(request + " , 欢迎使用 Netty WebScoket服务，现在时刻:" + new Date().toString()));
    }

    private static void sendHttpResponse(ChannelHandlerContext ctx, FullHttpRequest req, FullHttpResponse res) {
        // 返回应答给客户端
        if (res.getStatus().code() != 200) {
            ByteBuf buf = Unpooled.copiedBuffer(res.getStatus().toString(), CharsetUtil.UTF_8);
            res.content().writeBytes(buf);
            buf.release();
            setContentLength(res, res.content().readableBytes());
        }
        // 如果是非 Keep-Alive ,关闭连接
        ChannelFuture f = ctx.channel().writeAndFlush(res);
        if (!isKeepAlive(req) || res.getStatus().code() != 200) {
            f.addListener(ChannelFutureListener.CLOSE);
        }
    }

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

test.html

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    Netty WebSocket 时间服务器
</head>
<br>
<body>
<br>
<script type="text/javascript">
    var socket;
    if (!window.WebSocket) {
        window.WebSocket = window.MozWebSocket;
    }
    if (window.WebSocket) {
        socket = new WebSocket("ws://localhost:8080/websocket");
        socket.onmessage = function (event) {
            var ta = document.getElementById('responseText');
            ta.value = "";
            ta.value = event.data
        };
        socket.onopen = function (event) {
            var ta = document.getElementById('responseText');
            ta.value = "打开WebSocket服务正常，浏览器支持WebSocket!";
        };
        socket.onclose = function (event) {
            var ta = document.getElementById('responseText');
            ta.value = "";
            ta.value = "WebSocket 关闭!";
        };
    }
    else {
        alert("抱歉，您的浏览器不支持WebSocket协议!");
    }
    function send(message) {
        if (!window.WebSocket) {
            return;
        }
        if (socket.readyState == WebSocket.OPEN) {
            socket.send(message);
        }
        else {
            alert("WebSocket连接没有建立成功!");
        }
    }
</script>
<form onsubmit="return false;">
    <input type="text" name="message" value="Netty最佳实践"/>
    <br><br>
    <input type="button" value="发送WebSocket请求消息" onclick="send(this.form.message.value)"/>
    <hr color="blue"/>
    <h3>服务端返回的应答消息</h3>
    <textarea id="responseText" style="500px;height:300px;"></textarea>
</form>
</body>
</html>

启动的时候先启动 WebSocketServer，然后用浏览器打开test.html,点击 “发送WebSocket请求消息” 就会返回

Netty最佳实践 , 欢迎使用 Netty WebScoket服务，现在时刻:+new Date();

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