看完让你彻底搞懂Websocket原理，附通过netty完成Websocket( 二 ) _Websocket

1.申请一个WebSocket对象，并传入WebSocket地址信息，这时client会通过Http先发起握手请求

GET /chat HTTP/1.1Host: server.example.comUpgrade: websocket //告诉服务端需要将通信协议升级到websocketConnection: UpgradeSec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ== //浏览器base64加密的密钥，server端收到后需要提取Sec-WebSocket-Key 信息，然后加密。Origin: http://example.comSec-WebSocket-Protocol: chat, superchat //表?客?端请求提供的可供选择的?协议Sec-WebSocket-Version: 13 //版本标识

2.服务端响应、并建立连接

HTTP/1.1 101 Switching ProtocolsUpgrade: websocketConnection: UpgradeSec-WebSocket-Accept: SIEylb7zRYJAEgiqJXaOW3V+ZWQ=

3.握手成功促发客户端 onOpen 事件

连接状态查看

通过ws.readyState 可查看当前连接状态可选值

CONNECTING (0)：表示还没建立连接。
OPEN (1)：已经建立连接，可以进行通讯。
CLOSING (2)：通过关闭握手，正在关闭连接。
CLOSED (3)：连接已经关闭或无法打开。

（二）netty实现websocket演示
源码：https://github.com/limingIOS/netFuture/tree/master/源码/『互联网架构』软件架构-io与nio线程模型reactor模型（上）（53）/nio

源码：websocket
WebsocketServer.java

package com.dig8.websocket;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
public class WebsocketServer {
public static void main(String[] args) throws InterruptedException {
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
try{
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
.handler(new LoggingHandler(LogLevel.INFO))
.childHandler(new WebSocketChannelInitializer());
ChannelFuture channelFuture = serverBootstrap.bind(8989).sync();
channelFuture.channel().closeFuture().sync();
}finally{
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}

WebSocketChannelInitializer.java

package com.dig8.websocket;
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;
public class WebSocketChannelInitializer extends ChannelInitializer<SocketChannel> {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
//HttpServerCodec: 针对http协议进行编解码
pipeline.addLast("httpServerCodec", new HttpServerCodec());
//ChunkedWriteHandler分块写处理，文件过大会将内存撑爆
pipeline.addLast("chunkedWriteHandler", new ChunkedWriteHandler());
/**
* 作用是将一个Http的消息组装成一个完成的HttpRequest或者HttpResponse，那么具体的是什么
* 取决于是请求还是响应, 该Handler必须放在HttpServerCodec后的后面
*/
pipeline.addLast("httpObjectAggregator", new HttpObjectAggregator(8192));
//用于处理websocket, /ws为访问websocket时的uri
pipeline.addLast("webSocketServerProtocolHandler", new WebSocketServerProtocolHandler("/ws"));
pipeline.addLast("myWebSocketHandler", new WebSocketHandler());
}
}

WebSocketHandler.java

package com.dig8.websocket;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import java.util.Date;
public class WebSocketHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {
@Override
protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception {
Channel channel = ctx.channel();
System.out.println(channel.remoteAddress() + ": " + msg.text());
ctx.channel().writeAndFlush(new TextWebSocketFrame("来自服务端: " + new Date().toString()));