搭建WebSocket服务器与客户端

市场上有几款比较好的开源库供使用，比如PyWebSocket,WebSocket-Node, LibWebSockets等，这些库文件已经实现了WebSocket数据包的封装和解析，我们可以调用这些接口减少工作量。

1.     PyWebSocket

PyWebSocket采用Python语言编写，可以很好的跨平台，扩展起来也比较简单，目前WebKit采用它搭建WebSocket服务器来做LayoutTest，参见http://code.google.com/p/pywebsocket/

2.WebSocket-Node

WebSocket-Node采用JavaScript语言编写，这个库是建立在nodejs之上的，参见https://github.com/Worlize/Websocket-Node

3. LibWebSockets

LibWebSockets采用C/C++语言编写，可定制化的力度更大，从TCP监听开始到封包的完成我们都可以参与编程。参见git://git.warmcat.com/libwebsockets

4.Netty

采用了 Netty 中的 NIO 来构建 WebSocket 后端，参见：https://github.com/netty/netty

一.下面介绍一下用Netty搭建WebSocket服务器

1.WebsocketChatServer .java

package com.waylau.netty.demo.websocketchat;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;

/**
 * Websocket 聊天服务器-服务端
 * 
 * @author waylau.com
 * @date 2015-3-7
 */
public class WebsocketChatServer {

    private int port;

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

    public void run() throws Exception {
        
        EventLoopGroup bossGroup = new NioEventLoopGroup(); 
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
             .channel(NioServerSocketChannel.class) // (3)
             .childHandler(new WebsocketChatServerInitializer())  //处理初始化类
             .option(ChannelOption.SO_BACKLOG, 128)          
             .childOption(ChannelOption.SO_KEEPALIVE, true); // 保持长连接
            
    		System.out.println("WebsocketChatServer 启动了" + port);
    		
            // 绑定端口，开始接收进来的连接
            ChannelFuture f = b.bind(port).sync(); // (7)

            // 等待服务器  socket 关闭 。
            // 在这个例子中，这不会发生，但你可以优雅地关闭你的服务器。
            f.channel().closeFuture().sync();

        } finally {
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
            
    		System.out.println("WebsocketChatServer 关闭了");
        }
    }

    public static void main(String[] args) throws Exception {
        int port;
        if (args.length > 0) {
            port = Integer.parseInt(args[0]);
        } else {
            port = 8080;
        }
        new WebsocketChatServer(port).run();
    }
}

2.服务端 ChannelInitializer

package com.waylau.netty.demo.websocketchat;

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;

/**
 * 服务端 ChannelInitializer
 *
 * @author
 * @date 2015-3-13
 */
public class WebsocketChatServerInitializer extends
		ChannelInitializer<SocketChannel> {	//1

	@Override
    public void initChannel(SocketChannel ch) throws Exception {//2
		 ChannelPipeline pipeline = ch.pipeline();

        pipeline.addLast(new HttpServerCodec());
		pipeline.addLast(new HttpObjectAggregator(64*1024));
		pipeline.addLast(new ChunkedWriteHandler());
		pipeline.addLast(new HttpRequestHandler("/ws"));
		pipeline.addLast(new WebSocketServerProtocolHandler("/ws"));
		pipeline.addLast(new TextWebSocketFrameHandler());
    }
}

3.处理TextWebSocketFrame

package com.waylau.netty.demo.websocketchat;


import io.netty.channel.Channel;
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;

/**
 * 处理TextWebSocketFrame
 * 
 * @author 
 * 2015年3月26日
 */
public class TextWebSocketFrameHandler extends
		SimpleChannelInboundHandler<TextWebSocketFrame> {
	
	public static ChannelGroup channels = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
	
	@Override
	protected void channelRead0(ChannelHandlerContext ctx,
			TextWebSocketFrame msg) throws Exception { // 读取数据并转发
		Channel incoming = ctx.channel();
		for (Channel channel : channels) {
            if (channel != incoming){
                channel.writeAndFlush(new TextWebSocketFrame(msg.text()));
            } else {
            	channel.writeAndFlush(new TextWebSocketFrame(msg.text()));
            }
        }
	}
	
	@Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {  // 连接时调用
        Channel incoming = ctx.channel();
        
        // Broadcast a message to multiple Channels
        channels.writeAndFlush(new TextWebSocketFrame("[SERVER] - " + incoming.remoteAddress() + " 加入"));
        
        channels.add(incoming);
		System.out.println("Client:"+incoming.remoteAddress() +"加入");
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {  // 移除时调用
        Channel incoming = ctx.channel();
        
        // Broadcast a message to multiple Channels
        channels.writeAndFlush(new TextWebSocketFrame("[SERVER] - " + incoming.remoteAddress() + " 离开"));
        
		System.out.println("Client:"+incoming.remoteAddress() +"离开");

        // A closed Channel is automatically removed from ChannelGroup,
        // so there is no need to do "channels.remove(ctx.channel());"
    }
	    
	@Override
	public void channelActive(ChannelHandlerContext ctx) throws Exception { // 
        Channel incoming = ctx.channel();
		System.out.println("Client:"+incoming.remoteAddress()+"在线");
	}
	
	@Override
	public void channelInactive(ChannelHandlerContext ctx) throws Exception { // 
        Channel incoming = ctx.channel();
		System.out.println("Client:"+incoming.remoteAddress()+"掉线");
	}
	
	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)	// 异常则关闭
			throws Exception {
    	Channel incoming = ctx.channel();
		System.out.println("Client:"+incoming.remoteAddress()+"异常");
        // 当出现异常就关闭连接
        cause.printStackTrace();
        ctx.close();
	}
}

二.,客户端

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>WebSocket Chat</title>
</head>
<body>
	<script type="text/javascript">
		var socket;
		if (!window.WebSocket) {
			window.WebSocket = window.MozWebSocket;
		}
		if (window.WebSocket) {
			socket = new WebSocket("ws://192.169.1.101:8080/ws");
			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 = "连接开启!";
			};
			socket.onclose = function(event) {
				var ta = document.getElementById("responseText");
				ta.value = ta.value + "连接被关闭";
			};
		} else {
			alert("你的浏览器不支持 WebSocket！");
		}

		function send(message) {
			if (!window.WebSocket) {
				return;
			}
			if (socket.readyState == WebSocket.OPEN) {
				socket.send(message);
			} else {
				alert("连接没有开启.");
			}
		}
	</script>
	<form onsubmit="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="Welcome to www.waylau.com">
		<input type="button" value="发送消息" onclick="send(this.form.message.value)">
		<input type="button" onclick="javascript:document.getElementById("responseText").value=""" value="清空聊天记录">
	</form>
	<br> 
	<br> 
</body>
</html>

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