websocket 入门系列：三 netty实现简单聊天

一 序

接在上一篇《websocket入门系列:二Tomcat实现》

书上第11章写了个demo。我基于此修改下实现。netty的版本是4.17final

二 server端

package com.netty.websocket;import java.util.Map;import java.util.concurrent.ConcurrentHashMap;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import io.netty.bootstrap.ServerBootstrap;import io.netty.channel.Channel;import io.netty.channel.ChannelFuture;import io.netty.channel.ChannelFutureListener;import io.netty.channel.ChannelId;import io.netty.channel.ChannelInitializer;import io.netty.channel.ChannelPipeline;import io.netty.channel.EventLoopGroup;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 { private static final Logger logger = LoggerFactory.getLogger(WebSocketServer.class);     /**      * 保存所有WebSocket连接      */      private Map<ChannelId, Channel> channelMap = new ConcurrentHashMap<ChannelId, Channel>();       private static final int MAX_CONTENT_LENGTH = 65536;      // ------------------------ member fields -----------------------            private String host; // 绑定的地址      private int port; // 绑定的端口                  public WebSocketServer(String host, int port) {          this.host = host;          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)    .childHandler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {    ChannelPipeline pipeline = ch.pipeline();    // 保存该Channel的引用                  channelMap.put(ch.id(), ch);                ch.closeFuture().addListener(new ChannelFutureListener() {                                        public void operationComplete(ChannelFuture future) throws Exception {                        logger.info("channel close {}", future.channel());                          // Channel 关闭后不再引用该Channel                        channelMap.remove(future.channel().id());                      }                });      pipeline.addLast("http-codec",  new HttpServerCodec());    pipeline.addLast("aggregator",  new HttpObjectAggregator(MAX_CONTENT_LENGTH));    pipeline.addLast("http-chunked", new ChunkedWriteHandler());    pipeline.addLast("handler",  new WebSocketServerHandler(channelMap));}    });    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();} finally {    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("127.0.0.1",port).run();    }}

对应的

package com.netty.websocket;import java.util.Map;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import io.netty.channel.Channel;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelId;import io.netty.channel.SimpleChannelInboundHandler;import io.netty.handler.codec.http.FullHttpRequest;import io.netty.handler.codec.http.HttpHeaderNames;import io.netty.handler.codec.http.HttpHeaders;import io.netty.handler.codec.http.HttpMethod;import io.netty.handler.codec.http.websocketx.CloseWebSocketFrame;import io.netty.handler.codec.http.websocketx.PingWebSocketFrame;import io.netty.handler.codec.http.websocketx.PongWebSocketFrame;import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;import io.netty.handler.codec.http.websocketx.WebSocketFrame;import io.netty.handler.codec.http.websocketx.WebSocketServerHandshaker;import io.netty.handler.codec.http.websocketx.WebSocketServerHandshakerFactory;import io.netty.util.AttributeKey;public class WebSocketServerHandler extends SimpleChannelInboundHandler<Object> {private static final Logger logger = LoggerFactory.getLogger(WebSocketServerHandler.class);    private static final String WEBSOCKET_UPGRADE = "websocket";      private static final String WEBSOCKET_CONNECTION = "Upgrade";      private final String WEBSOCKET_URI_ROOT ="ws://127.0.0.1:8080";      // handshaker attachment key      private static final AttributeKey<WebSocketServerHandshaker> ATTR_HANDSHAKER = AttributeKey.newInstance("ATTR_KEY_CHANNELID");    /**      * 保存所有WebSocket连接      */      private Map<ChannelId, Channel> channelMap ;        public WebSocketServerHandler(Map channelMap){    this.channelMap = channelMap;    }        @Override    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {ctx.flush();    }    private void handleHttpRequest(ChannelHandlerContext ctx,    FullHttpRequest req) throws Exception {if (isWebSocketUpgrade(req)) { // 该请求是不是websocket upgrade请求           logger.info("upgrade to websocket protocol");                    String subProtocols = req.headers().get(HttpHeaderNames.SEC_WEBSOCKET_PROTOCOL);                    WebSocketServerHandshakerFactory factory = new WebSocketServerHandshakerFactory(WEBSOCKET_URI_ROOT, subProtocols, false);          WebSocketServerHandshaker handshaker = factory.newHandshaker(req);                    if (handshaker == null) {// 请求头不合法, 导致handshaker没创建成功              WebSocketServerHandshakerFactory.sendUnsupportedVersionResponse(ctx.channel());          } else {              // 响应该请求              handshaker.handshake(ctx.channel(), req);              // 把handshaker 绑定给Channel, 以便后面关闭连接用              ctx.channel().attr(ATTR_HANDSHAKER).set(handshaker);// attach handshaker to this channel          }          return;      }// TODO 忽略普通http请求      logger.info("ignoring normal http request");      }           private void handleWebSocketFrame(ChannelHandlerContext ctx,    WebSocketFrame frame) {      // text frame          if (frame instanceof TextWebSocketFrame) {              String text = ((TextWebSocketFrame) frame).text();              for (Channel ch : channelMap.values()) {              TextWebSocketFrame rspFrame = new TextWebSocketFrame(text);              logger.info("recieve TextWebSocketFrame from channel {}", ctx.channel());              // 发给其他所有channel  //   //                if (ctx.channel().equals(ch)) {   //                    continue;   //                }                  ch.writeAndFlush(rspFrame);                  logger.info("write text[{}] to channel {}", text, ch);              }              return;          }                    // ping frame, 回复pong frame即可          if (frame instanceof PingWebSocketFrame) {              logger.info("recieve PingWebSocketFrame from channel {}", ctx.channel());              ctx.channel().writeAndFlush(new PongWebSocketFrame(frame.content().retain()));              return;          }                    if (frame instanceof PongWebSocketFrame) {              logger.info("recieve PongWebSocketFrame from channel {}", ctx.channel());              return;          }          // close frame,           if (frame instanceof CloseWebSocketFrame) {              logger.info("recieve CloseWebSocketFrame from channel {}", ctx.channel());              WebSocketServerHandshaker handshaker = ctx.channel().attr(ATTR_HANDSHAKER).get();              if (handshaker == null) {                  logger.error("channel {} have no HandShaker", ctx.channel());                  return;              }              handshaker.close(ctx.channel(), (CloseWebSocketFrame) frame.retain());              return;          }          // 剩下的是binary frame, 忽略          logger.warn("unhandle binary frame from channel {}", ctx.channel());      }      @Override    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)    throws Exception {cause.printStackTrace();ctx.close();    }@Overrideprotected void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {// TODO Auto-generated method stublogger.info("receive msg:"+msg.toString());// 传统的HTTP接入if (msg instanceof FullHttpRequest) {    handleHttpRequest(ctx, (FullHttpRequest) msg);}// WebSocket接入else if (msg instanceof WebSocketFrame) {    handleWebSocketFrame(ctx, (WebSocketFrame) msg);}}//三者与：1.GET? 2.Upgrade头 包含websocket字符串?  3.Connection头 包含 Upgrade字符串?      private boolean isWebSocketUpgrade(FullHttpRequest req) {          HttpHeaders headers = req.headers();          return req.method().equals(HttpMethod.GET)                   && headers.get(HttpHeaderNames.UPGRADE).contains(WEBSOCKET_UPGRADE)                  && headers.get(HttpHeaderNames.CONNECTION).contains(WEBSOCKET_CONNECTION);      }      }

这里面是主要业务逻辑的实现。对应websocket的协议，识别出握手过程，对于传输的数据帧类型进行不同的业务处理。

里面有一些细节。注意一个异常：

io.netty.util.IllegalReferenceCountException: refCnt: 0

三 测试

这里的测试，修改下地址：

web页面起了Tomcat。端口80，websocket的端口避免冲突：改为8080

web页面代码不再重复发了，参见上一篇，

分别打开火狐，Chrome浏览器。client模拟发一句：

package com.websocket.client;import java.io.IOException;import java.net.URI;import java.util.concurrent.CountDownLatch;import javax.websocket.ContainerProvider;import javax.websocket.DeploymentException;import javax.websocket.Session;import javax.websocket.WebSocketContainer;public class Test {public static void main(String[] args) throws DeploymentException, IOException, InterruptedException {        WebSocketContainer ws = ContainerProvider.getWebSocketContainer();        String url = "ws://127.0.0.1:8080";        MyClient client = new MyClient();        Session session =  ws.connectToServer(client, URI.create(url));         int turn = 0;               session.getBasicRemote().sendText("client send: " + turn);            Thread.sleep(1000);                new CountDownLatch(1).await();          }}

Java的client输出：

I was accpeted by her!客户端收到消息: client send: 0客户端收到消息: chrome客户端收到消息: hi,ff

页面的输出截屏：

*****************************************************************************

这里只是参照书上例子休简单的实现群发消息的demo.

还得深入学习netty，不然除了异常很难去修复。

参考：

http://lixiaohui.iteye.com/blog/2328183