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基于netty的websocket开发小结 博客分类: java编程 javahtml5websocket 

程序员文章站 2024-03-06 19:19:50
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WebSocket是html5规范新引入的功能,用于解决浏览器与后台服务器双向通讯的问题,使用WebSocket技术,后台可以随时向前端推送消息,以保证前后台状态统一,在传统的无状态HTTP协议中,这是“无法做到”的。

WebSocket提出之前,为了解决后台推送消息到前台的需求,提出了一些解决方案,这些方案使用已有的技术(如ajax,iframe,flashplayer,java applet ...),通过一些变通的处理来实现。

webSocket是html5新引入的技术,允许后台随时向前端发送文本或者二进制消息,WebSocket是一种全新的协议,不属于http无状态协议,协议名为"ws",这意味着一个websocket连接地址会是这样的写法:
ws://127.0.0.1:8080/websocket。ws不是http,所以传统的web服务器不一定支持,需要服务器与浏览器同时支持, WebSocket才能正常运行,目前的支持还不普遍,需要特别的web服务器和现代的浏览器。

浏览器对WebSocket的支持
Google Chrome浏览器最先支持WebSocket,随后是Safari,Firefox,此外最新版本的Opera和IE(Opera11,IE10)也支持WebSocket。

客户端WebSocket的主要方法

1 构造函数
 var websocket = new WebSocket("ws://127.0.0.1:8080/websocket");

2 事件open/message/close/error
WebSocket#onopen, onmessage, onclose, onerror
连接打开时,回调onopen方法,接收到后台消息时会触发到onmessage事件,后台关闭时调用onclose,出现连接异常时可在onerror中捕获
发送消息 - WebSocket#send(data)
关闭连接 - WebSocket#close(optional code, optional reason)

下面是一个简单的html5连接websocket服务器测试页
<!DOCTYPE html>
<html>
<head>

<script type="text/javascript" charset="utf-8" >
  window.WebSocket = window.WebSocket || window.MozWebSocket;
  
 if (!window.WebSocket){
     alert("WebSocket not supported by this browser");
     return;
 };
  
var websocket = new WebSocket("ws://127.0.0.1:8080/websocket");
 websocket.onmessage = function(evt){
     var data = evt.data;
      alert("received message: " + data);
 }

 function send() {
 var name = document.querySelector("input[name=name]").value;
    alert("websocket send message:"+name);
    websocket.send(name);
 }
</script>
</head>
<body>
<label for="name">What’s your name:</label>
<input type="text" id="name" name="name" />
<button onclick="send()">Send</button>
<div id="message" style="color:red"></div>
</body>
</html>


服务器对WebSocket的支持
    WebSocket不同于http协议,传统的web服务器通常不支持WebSocket.而websocket服务器端的开发大概有借助Socket.IO开发、NodeJS和Socket.IO联合开发以及借助netty框架开发等等。这里只对netty框架下的websocket开发进行一个简单的说明!

    websocket的协议比较简单, 客户端和普通的浏览器一样通过80或者443端口和服务器进行请求握手,服务器根据http header识别是否一个websocket请求,如果是,则将请求升级为一个websocket连接,握手成功后就进入双向长连接的数据传输阶段. websocket的数据传输是基于帧的方式: 0x00 表示数据开始, 0xff表示数据结束,数据以utf-8编码.

    简单的说,第一次请求客户端发送的是http请求,请求头中包含websocket相关的信息,服务器端对请求进行验证:

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

        // Send the demo page and favicon.ico
        if (req.getUri().equals("/")) {
            HttpResponse res = new DefaultHttpResponse(HTTP_1_1, OK);

            ChannelBuffer content = WebSocketServerIndexPage.getContent(getWebSocketLocation(req));

            res.setHeader(CONTENT_TYPE, "text/html; charset=UTF-8");
            setContentLength(res, content.readableBytes());

            res.setContent(content);
            sendHttpResponse(ctx, req, res);
            return;
        } else if (req.getUri().equals("/favicon.ico")) {
            HttpResponse res = new DefaultHttpResponse(HTTP_1_1, NOT_FOUND);
            sendHttpResponse(ctx, req, res);
            return;
        }

        // Handshake
        WebSocketServerHandshakerFactory wsFactory = new WebSocketServerHandshakerFactory(
                this.getWebSocketLocation(req), null, false);
        this.handshaker = wsFactory.newHandshaker(req);
        if (this.handshaker == null) {
            wsFactory.sendUnsupportedWebSocketVersionResponse(ctx.getChannel());
        } else {
            this.handshaker.handshake(ctx.getChannel(), req);
            System.out.println(WebSocketServer.recipients.size());
            WebSocketServer.recipients.add(ctx.getChannel());
            System.out.println(WebSocketServer.recipients.size());
            System.out.println(ctx.getChannel().getId());
        }
    }


验证成功后,将请求升级为一个websocket连接,之后的通信就进入双向长连接的数据传输阶段。

    private void handleWebSocketFrame(ChannelHandlerContext ctx, WebSocketFrame frame) {

        // Check for closing frame
        if (frame instanceof CloseWebSocketFrame) {
            this.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()));
        }

        // Send the uppercase string back.
        String request = ((TextWebSocketFrame) frame).getText();
        logger.debug(String.format("Channel %s received %s", ctx.getChannel().getId(), request));

//        WebSocketServer.recipients.write(new TextWebSocketFrame(request.toUpperCase()));
        ctx.getChannel().write(new TextWebSocketFrame(request.toUpperCase()));
    }


一定要注意在messageReceived中要对HttpRequest和WebSocketFrame分别进行处理。
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
        Object msg = e.getMessage();
        if (msg instanceof HttpRequest) {
            handleHttpRequest(ctx, (HttpRequest) msg);
        } else if (msg instanceof WebSocketFrame) {
            handleWebSocketFrame(ctx, (WebSocketFrame) msg);
        }
    }


服务入口
package com.etao.mobile.websocket;

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

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

/**
 * A HTTP server which serves Web Socket requests at:
 * 
 * http://localhost:8080/websocket
 * 
 * Open your browser at http://localhost:8080/, then the demo page will be
 * loaded and a Web Socket connection will be made automatically.
 * 
 * This server illustrates support for the different web socket specification
 * versions and will work with:
 * 
 * <ul>
 * <li>Safari 5+ (draft-ietf-hybi-thewebsocketprotocol-00)
 * <li>Chrome 6-13 (draft-ietf-hybi-thewebsocketprotocol-00)
 * <li>Chrome 14+ (draft-ietf-hybi-thewebsocketprotocol-10)
 * <li>Chrome 16+ (RFC 6455 aka draft-ietf-hybi-thewebsocketprotocol-17)
 * <li>Firefox 7+ (draft-ietf-hybi-thewebsocketprotocol-10)
 * </ul>
 */
public class WebSocketServer {

	private final int port;

	public static ChannelGroup recipients = new DefaultChannelGroup();

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

	public void run() {
		// Configure the server.
		ServerBootstrap bootstrap = new ServerBootstrap(
				new NioServerSocketChannelFactory(Executors
						.newCachedThreadPool(), Executors.newCachedThreadPool()));

		// Set up the event pipeline factory.
		bootstrap.setPipelineFactory(new WebSocketServerPipelineFactory());

		// Bind and start to accept incoming connections.
		bootstrap.bind(new InetSocketAddress(port));

		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();
	}
}


一定要注意的是netty3.0一下的版本是不支持websocket的!我这里用的是3.3.0.Final版本。

可能存在的隐患:不同草案的websocket 握手标准有所不同,因此netty在这方面的检测是否可以满足要求?

我这里也参考了 基于Websocket草案10协议的升级及基于Netty的握手实现,在此对冯立彬的博客表示感谢!