基于Netty实现WebSocket客户端_netty websocket 客户端

本文是基于Netty快速上手WebSocket客户端，不涉及WebSocket的TLS/SSL加密传输。

WebSocket原理参考【WebSocket简介-CSDN博客】，测试用的WebSocket服务端也是用Netty实现的，参考【基于Netty实现WebSocket服务端-CSDN博客】

一、基于Netty快速实现WebSocket客户端

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.http.DefaultHttpHeaders;
import io.netty.handler.codec.http.HttpClientCodec;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketClientHandshakerFactory;
import io.netty.handler.codec.http.websocketx.WebSocketClientProtocolHandler;
import io.netty.handler.codec.http.websocketx.WebSocketVersion;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import io.netty.handler.stream.ChunkedWriteHandler;
import lombok.extern.slf4j.Slf4j;
 
import java.net.URI;
import java.util.concurrent.CountDownLatch;
 
/**
 * https://blog.csdn.net/a1053765496/article/details/130701218
 * 基于Netty快速实现WebSocket客户端，不手动处理握手
 */
@Slf4j
public class SimpleWsClient {
 
    final CountDownLatch latch = new CountDownLatch(1);
 
    public static void main(String[] args) throws Exception {
        SimpleWsClient client = new SimpleWsClient();
        client.test();
    }
 
    public void test() throws Exception {
        Channel dest = dest();
        latch.await();
        dest.writeAndFlush(new TextWebSocketFrame("CountDownLatch完成后发送的消息"));
    }
 
    public Channel dest() throws Exception {
        final URI webSocketURL = new URI("ws://127.0.0.1:7070/helloWs");
 
        EventLoopGroup group = new NioEventLoopGroup();
        Bootstrap boot = new Bootstrap();
        boot.option(ChannelOption.SO_KEEPALIVE, true)
            .option(ChannelOption.TCP_NODELAY, true)
            .group(group)
            .handler(new LoggingHandler(LogLevel.INFO))
            .channel(NioSocketChannel.class)
            .handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel sc) throws Exception {
                    ChannelPipeline pipeline = sc.pipeline();
                    pipeline.addLast(new HttpClientCodec());
                    pipeline.addLast(new ChunkedWriteHandler());
                    pipeline.addLast(new HttpObjectAggregator(64 * 1024));
                    pipeline.addLast(new WebSocketClientProtocolHandler(WebSocketClientHandshakerFactory
                        .newHandshaker(webSocketURL, WebSocketVersion.V13, null, false, new DefaultHttpHeaders())));
                    pipeline.addLast(new SimpleChannelInboundHandler<TextWebSocketFrame>() {
 
                        @Override
                        protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg)
                            throws Exception {
                            System.err.println(" 客户端收到消息======== " + msg.text());
                        }
 
                        @Override
                        public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
                            if (WebSocketClientProtocolHandler.ClientHandshakeStateEvent.HANDSHAKE_COMPLETE
                                .equals(evt)) {
                                log.info(ctx.channel().id().asShortText() + " 握手完成！");
                                latch.countDown();
                                send(ctx.channel());
                            }
                            super.userEventTriggered(ctx, evt);
                        }
                    });
 
                }
            });
 
        ChannelFuture cf = boot.connect(webSocketURL.getHost(), webSocketURL.getPort()).sync();
 
        return cf.channel();
    }
 
    public static void send(Channel channel) {
        final String textMsg = "握手完成后直接发送的消息";
 
        if (channel != null && channel.isActive()) {
            TextWebSocketFrame frame = new TextWebSocketFrame(textMsg);
            channel.writeAndFlush(frame).addListener((ChannelFutureListener) channelFuture -> {
                if (channelFuture.isDone() && channelFuture.isSuccess()) {
                    log.info("     ================= 发送成功.");
                } else {
                    channelFuture.channel().close();
                    log.info("     ================= 发送失败. cause = " + channelFuture.cause());
                    channelFuture.cause().printStackTrace();
                }
            });
        } else {
            log.error("消息发送失败！ textMsg = " + textMsg);
        }
    }
 
}

这里我们不手动进行握手，由Netty通过WebSocketClientProtocolHandler进行握手，但是我们要知道何时握手完成了。握手完成了我们才能进行正常的消息读写。

握手事件是在自定义的Handler中实现的，这里为了方便使用CountDownLatch，使用了匿名内部类SimpleChannelInboundHandler的方式。userEventTriggered这个方法会接收到所有的事件，其中就包括握手完成事件。

二、基于Netty，手动处理WebSocket握手信息：

客户端启动代码：

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
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.NioSocketChannel;
import io.netty.handler.codec.http.DefaultHttpHeaders;
import io.netty.handler.codec.http.HttpClientCodec;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.websocketx.CloseWebSocketFrame;
import io.netty.handler.codec.http.websocketx.PingWebSocketFrame;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketClientHandshakerFactory;
import io.netty.handler.codec.http.websocketx.WebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketVersion;
 
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URI;
 
/**
 * https://gitcode.com/ddean2009/learn-netty4/tree/master/src/main/java/com/flydean25/socketclient
 * https://www.flydean.com/25-netty-websocket-client
 * https://blog.csdn.net/superfjj/article/details/120648434
 * https://blog.csdn.net/twypx/article/details/84543518
 */
public final class NettyWsClient {
 
    static final String URL = System.getProperty("url", "ws://127.0.0.1:7070/helloWs");
 
    public static void main(String[] args) throws Exception {
        URI uri = new URI(URL);
        final int port = uri.getPort();
 
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            WebSocketClientHandler handler = new WebSocketClientHandler(WebSocketClientHandshakerFactory
                .newHandshaker(uri, WebSocketVersion.V13, null, true, new DefaultHttpHeaders()));
 
            Bootstrap b = new Bootstrap();
            b.group(group).channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) {
                    ChannelPipeline p = ch.pipeline();
                    p.addLast(new HttpClientCodec(), new HttpObjectAggregator(8192), handler);
                }
            });
 
            Channel ch = b.connect(uri.getHost(), port).sync().channel();
            handler.handshakeFuture().sync();
 
            BufferedReader console = new BufferedReader(new InputStreamReader(System.in));
            while (true) {
                String msg = console.readLine();
                if (msg == null) {
                    break;
                } else if ("再见".equalsIgnoreCase(msg)) {
                    ch.writeAndFlush(new CloseWebSocketFrame());
                    ch.closeFuture().sync();
                    break;
                } else if ("ping".equalsIgnoreCase(msg)) {
                    WebSocketFrame frame = new PingWebSocketFrame(Unpooled.wrappedBuffer(new byte[] {8, 1, 8, 1}));
                    ch.writeAndFlush(frame);
                } else {
                    WebSocketFrame frame = new TextWebSocketFrame(msg);
                    ch.writeAndFlush(frame);
                }
            }
        } finally {
            group.shutdownGracefully();
        }
    }
}

客户端Handler

import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPromise;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.websocketx.CloseWebSocketFrame;
import io.netty.handler.codec.http.websocketx.PongWebSocketFrame;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketClientHandshaker;
import io.netty.handler.codec.http.websocketx.WebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketHandshakeException;
import io.netty.util.CharsetUtil;
import lombok.extern.slf4j.Slf4j;
 
@Slf4j
public class WebSocketClientHandler extends SimpleChannelInboundHandler<Object> {
 
    private final WebSocketClientHandshaker handshaker;
 
    private ChannelPromise handshakeFuture;
 
    public WebSocketClientHandler(WebSocketClientHandshaker handshaker) {
        this.handshaker = handshaker;
    }
 
    public ChannelFuture handshakeFuture() {
        return handshakeFuture;
    }
 
    @Override
    public void handlerAdded(ChannelHandlerContext ctx) {
        handshakeFuture = ctx.newPromise();
    }
 
    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        log.info("channelActive, 进行handshake");
        handshaker.handshake(ctx.channel());
    }
 
    @Override
    public void channelInactive(ChannelHandlerContext ctx) {
        log.info("channelInactive!");
    }
 
    @Override
    public void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
        Channel ch = ctx.channel();
        if (!handshaker.isHandshakeComplete()) {
            try {
                handshaker.finishHandshake(ch, (FullHttpResponse) msg);
                log.info("websocket Handshake 完成!");
                handshakeFuture.setSuccess();
            } catch (WebSocketHandshakeException e) {
                log.info("websocket连接失败!");
                handshakeFuture.setFailure(e);
            }
            return;
        }
 
        if (msg instanceof FullHttpResponse) {
            FullHttpResponse response = (FullHttpResponse) msg;
            throw new IllegalStateException("Unexpected FullHttpResponse (getStatus=" + response.status() + ", content="
                + response.content().toString(CharsetUtil.UTF_8) + ')');
        }
 
        WebSocketFrame frame = (WebSocketFrame) msg;
        if (frame instanceof TextWebSocketFrame) {
            TextWebSocketFrame textFrame = (TextWebSocketFrame) frame;
            log.info("接收到TXT消息: " + textFrame.text());
        } else if (frame instanceof PongWebSocketFrame) {
            log.info("接收到pong消息");
        } else if (frame instanceof CloseWebSocketFrame) {
            log.info("接收到closing消息");
            ch.close();
        }
    }
 
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        // 异常处理
        log.error("出现异常", cause);
        if (!handshakeFuture.isDone()) {
            handshakeFuture.setFailure(cause);
        }
        ctx.close();
    }
}

可以看到，我们这里也要手动标记握手完成，是在自定义的Handler的channelRead0方法中标记的。

测试的时候，我们可以看到，当客户端发送ping的时候，服务端会自动回pong，这个是有Netty实现的服务端自带的心跳机制。

2024-05-25 16:35:10 INFO [WebSocketClientHandler] channelActive, 进行handshake
2024-05-25 16:35:10 INFO [WebSocketClientHandler] websocket Handshake 完成!
123
2024-05-25 16:35:26 INFO [WebSocketClientHandler] 接收到TXT消息: 2024-35-25 04:05:26: 123
ping
2024-05-25 16:35:52 INFO [WebSocketClientHandler] 接收到pong消息