[Java] Netty Websocket Server Javascript Client

作者: shagoo
发布时间:2015-07-29 11:25:19

WebSocket协议的出现无疑是 HTML5 中最令人兴奋的功能特性之一,它能够很好地替代Comet技术以及Flash的XmlSocket来实现基于HTTP协议的双向通信。目前主流的浏览器,如Chrome、Firefox、IE10、Opera10、Safari等都已经支持WebSocket。另外,在服务端也出现了一些不错的WebSocket项目,如Resin、Jetty7、pywebsocket等。不过,本文将介绍的是如何使用强大的Netty框架(Netty-3.5.7.Final)来实现WebSocket服务端。

Netty3框架的性能优势已无需多说,但更让开发者舒心的是,Netty3还为大家提供了非常丰富的协议实现,包括HTTP、Protobuf、WebSocket等,开发者们可以很轻松的实现自己的Socket Server。按照Netty3的常规思路,我们需要准备以下3个文件:

1、WebSocketServer.java
2、WebSocketServerHandler.java
3、WebSocketServerPipelineFactory.java


以上3个文件分别包含了主程序的逻辑、服务的处理逻辑以及Socket Pipeline的设置逻辑。Java代码实现如下:

WebSocketServer.java

import java.net.InetSocketAddress;
import java.util.concurrent.Executors;

import org.jboss.netty.bootstrap.ServerBootstrap;
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;

public class WebSocketServer
{
    private final int port;

    public WebSocketServer(int port) {
        this.port = port;
    }

    public void run() {
        // 设置 Socket channel factory
        ServerBootstrap bootstrap = new ServerBootstrap(
                new NioServerSocketChannelFactory(
                        Executors.newCachedThreadPool(),
                        Executors.newCachedThreadPool()));

        // 设置 Socket pipeline factory
        bootstrap.setPipelineFactory(new WebSocketServerPipelineFactory());

        // 启动服务,开始监听
        bootstrap.bind(new InetSocketAddress(port));

        // 打印提示信息
        System.out.println("Web socket server started at port " + port + '.');
        System.out.println("Open your browser and navigate to http://localhost:" + port + '/');
    }

    public static void main(String[] args) {
        int port;
        if (args.length > 0) {
            port = Integer.parseInt(args[0]);
        } else {
            port = 8080;
        }
        new WebSocketServer(port).run();
    }
}
WebSocketServerPipelineFactory.java
import static org.jboss.netty.channel.Channels.*;

import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.handler.codec.http.HttpChunkAggregator;
import org.jboss.netty.handler.codec.http.HttpRequestDecoder;
import org.jboss.netty.handler.codec.http.HttpResponseEncoder;

public class WebSocketServerPipelineFactory implements ChannelPipelineFactory {
    public ChannelPipeline getPipeline() throws Exception {
        // pipeline 的配置与 逻辑
        ChannelPipeline pipeline = pipeline();
        pipeline.addLast("decoder", new HttpRequestDecoder());
        pipeline.addLast("aggregator", new HttpChunkAggregator(65536));
        pipeline.addLast("encoder", new HttpResponseEncoder());
        pipeline.addLast("handler", new WebSocketServerHandler());
        return pipeline;
    }
}
WebSocketServerHandler.java
import static org.jboss.netty.handler.codec.http.HttpHeaders.*;
import static org.jboss.netty.handler.codec.http.HttpHeaders.Names.*;
import static org.jboss.netty.handler.codec.http.HttpMethod.*;
import static org.jboss.netty.handler.codec.http.HttpResponseStatus.*;
import static org.jboss.netty.handler.codec.http.HttpVersion.*;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.ChannelFutureListener;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelUpstreamHandler;
import org.jboss.netty.handler.codec.http.DefaultHttpResponse;
import org.jboss.netty.handler.codec.http.HttpHeaders;
import org.jboss.netty.handler.codec.http.HttpRequest;
import org.jboss.netty.handler.codec.http.HttpResponse;
import org.jboss.netty.handler.codec.http.websocketx.CloseWebSocketFrame;
import org.jboss.netty.handler.codec.http.websocketx.PingWebSocketFrame;
import org.jboss.netty.handler.codec.http.websocketx.PongWebSocketFrame;
import org.jboss.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import org.jboss.netty.handler.codec.http.websocketx.WebSocketFrame;
import org.jboss.netty.handler.codec.http.websocketx.WebSocketServerHandshaker;
import org.jboss.netty.handler.codec.http.websocketx.WebSocketServerHandshakerFactory;
import org.jboss.netty.logging.InternalLogger;
import org.jboss.netty.logging.InternalLoggerFactory;
import org.jboss.netty.util.CharsetUtil;

public class WebSocketServerHandler extends SimpleChannelUpstreamHandler
{
    private static final InternalLogger logger = InternalLoggerFactory
            .getInstance(WebSocketServerHandler.class);

    private static final String WEBSOCKET_PATH = "/websocket";

    private WebSocketServerHandshaker handshaker;

    @Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e)
            throws Exception {
        // 处理接受消息
        Object msg = e.getMessage();
        if (msg instanceof HttpRequest) {
            handleHttpRequest(ctx, (HttpRequest) msg);
        } else if (msg instanceof WebSocketFrame) {
            handleWebSocketFrame(ctx, (WebSocketFrame) msg);
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e)
            throws Exception {
        // 处理异常情况
        e.getCause().printStackTrace();
        e.getChannel().close();
    }

    private void handleHttpRequest(ChannelHandlerContext ctx, HttpRequest req)
            throws Exception {
        // 只接受 HTTP GET 请求
        if (req.getMethod() != GET) {
            sendHttpResponse(ctx, req, new DefaultHttpResponse(HTTP_1_1,
                    FORBIDDEN));
            return;
        }

        // Websocket 握手开始
        WebSocketServerHandshakerFactory wsFactory = new WebSocketServerHandshakerFactory(
                getWebSocketLocation(req), null, false);
        handshaker = wsFactory.newHandshaker(req);
        if (handshaker == null) {
            wsFactory.sendUnsupportedWebSocketVersionResponse(ctx.getChannel());
        } else {
            handshaker.handshake(ctx.getChannel(), req).addListener(
                    WebSocketServerHandshaker.HANDSHAKE_LISTENER);
        }
    }

    private void handleWebSocketFrame(ChannelHandlerContext ctx,
            WebSocketFrame frame) {
        // Websocket 握手结束
        if (frame instanceof CloseWebSocketFrame) {
            handshaker.close(ctx.getChannel(), (CloseWebSocketFrame) frame);
            return;
        } else if (frame instanceof PingWebSocketFrame) {
            ctx.getChannel().write(new PongWebSocketFrame(frame.getBinaryData()));
            return;
        } else if (!(frame instanceof TextWebSocketFrame)) {
            throw new UnsupportedOperationException(String.format("%s frame types not supported",
                    frame.getClass().getName()));
        }

        // 处理接受到的数据(转成大写)并返回
        String request = ((TextWebSocketFrame) frame).getText();
        if (logger.isDebugEnabled()) {
            logger.debug(String.format("Channel %s received %s", ctx.getChannel().getId(), request));
        }
        ctx.getChannel().write(new TextWebSocketFrame(request.toUpperCase()));
    }

    private static void sendHttpResponse(ChannelHandlerContext ctx,
            HttpRequest req, HttpResponse res) {
        // 返回 HTTP 错误页面
        if (res.getStatus().getCode() != 200) {
            res.setContent(ChannelBuffers.copiedBuffer(res.getStatus().toString(), CharsetUtil.UTF_8));
            setContentLength(res, res.getContent().readableBytes());
        }

        // 发送返回信息并关闭连接
        ChannelFuture f = ctx.getChannel().write(res);
        if (!isKeepAlive(req) || res.getStatus().getCode() != 200) {
            f.addListener(ChannelFutureListener.CLOSE);
        }
    }

    private static String getWebSocketLocation(HttpRequest req) {
        return "ws://" + req.getHeader(HttpHeaders.Names.HOST) + WEBSOCKET_PATH;
    }
}

以上代码的逻辑还是比较清晰的:首先,在WebSocketServer中设置WebSocketServerPipelineFactory;然后,在WebSocketServerPipelineFactory中设置WebSocketServerHandler;接着,在WebSocketServerHandler处理请求并返回结果;其中,最重要的处理逻辑位于handleWebSocketFrame方法中,也就是把获取到的请求信息全部转化成大写并返回。最后,运行WebSocketServer.java就可以启动WebSocket服务,监听本地的8080端口。至此,WebSocket服务端已经全部准备就绪。这里,其实我们已经同时开发了一个简单的HTTP服务器,界面截图如下:



接下来,我们需要准备使用Javascript实现的WebSocket客户端,实现非常简单,Javascript代码实现如下:

websocket.html
<html><head><title>Web Socket Client</title></head>
<body>
<script type="text/javascript">
var socket;
if (!window.WebSocket) {
    window.WebSocket = window.MozWebSocket;
}
// Javascript Websocket Client
if (window.WebSocket) {
    socket = new WebSocket("ws://localhost:8080/websocket");
    socket.onmessage = function(event) {
        var ta = document.getElementById('responseText');
        ta.value = ta.value + '\n' + event.data
    };
    socket.onopen = function(event) {
        var ta = document.getElementById('responseText');
        ta.value = "Web Socket opened!";
    };
    socket.onclose = function(event) {
        var ta = document.getElementById('responseText');
        ta.value = ta.value + "Web Socket closed";
    };
} else {
    alert("Your browser does not support Web Socket.");
}
// Send Websocket data
function send(message) {
    if (!window.WebSocket) { return; }
    if (socket.readyState == WebSocket.OPEN) {
        socket.send(message);
    } else {
        alert("The socket is not open.");
    }
}
</script>
<h3>Send :</h3>
<form onsubmit="return false;">
<input type="text" name="message" value="Hello World!"/><input type="button" value="Send Web Socket Data" onclick="send(this.form.message.value)" />
<h3>Receive :</h3>
<textarea id="responseText" style="width:500px;height:300px;"></textarea>
</form>
</body>
</html>

以上Javascript代码的逻辑很好理解:即创建一个指向对应WebSocket地址(ws://localhost:8080/websocket)的Socket连接,进而进行发送和获取操作。其实,我们只需要把websocket.html文件放置到任意的HTTP服务器上,并打开对应URL地址,就可以看到以下的Demo界面:



输入文字“Hello World”并点击“Send Web Socket Data”按钮就可以向WebSocket的服务端发送消息了。从上图中我们还可以看到,在“Receive”下方的输出框中看到返回的消息(大写过的HELLO WORLD文字),这样一次基本的信息交互就完成了。当然,此时如果把服务端关闭,输出框中则会看到“Web Socket closed”信息。

版权声明:本文为博主原创文章,未经博主允许不得转载。

来源:http://blog.csdn.net/shagoo/article/details/8028813

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