用java写一个netty websocket服务端和客户端代码实现互相通讯

以下是一个使用 Netty 实现 WebSocket 服务端和客户端的示例代码：

服务端代码：

public class WebSocketServer {
    public static void main(String[] args) throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            ServerBootstrap bootstrap = new ServerBootstrap()
                    .group(group)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new HttpServerCodec());
                            pipeline.addLast(new HttpObjectAggregator(65536));
                            pipeline.addLast(new WebSocketServerProtocolHandler("/chat"));
                            pipeline.addLast(new TextWebSocketFrameHandler());
                        }
                    });

            ChannelFuture future = bootstrap.bind(8080).sync();
            future.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }

    private static class TextWebSocketFrameHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {
        private final List<Channel> channels = new ArrayList<>();

        @Override
        protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception {
            String text = msg.text();
            System.out.println("Received message: " + text);

            for (Channel channel : channels) {
                channel.writeAndFlush(new TextWebSocketFrame("Server: " + text));
            }
        }

        @Override
        public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
            channels.add(ctx.channel());
        }

        @Override
        public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
            channels.remove(ctx.channel());
        }
    }
}

客户端代码：

public class WebSocketClient {
    public static void main(String[] args) throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            WebSocketClientHandler handler = new WebSocketClientHandler(WebSocketClientHandshakerFactory.newHandshaker(
                    new URI("ws://localhost:8080/chat"), WebSocketVersion.V13, null, false, new DefaultHttpHeaders()));

            Bootstrap bootstrap = new Bootstrap()
                    .group(group)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new HttpClientCodec());
                            pipeline.addLast(new HttpObjectAggregator(65536));
                            pipeline.addLast(new WebSocketClientProtocolHandler(handler.handshaker()));
                            pipeline.addLast(handler);
                        }
                    });

            Channel channel = bootstrap.connect("localhost", 8080).sync().channel();
            handler.handshakeFuture().sync();

            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
            while (true) {
                String line = reader.readLine();
                if (line == null) {
                    break;
                }
                channel.writeAndFlush(new TextWebSocketFrame(line));
            }
        } finally {
            group.shutdownGracefully();
        }
    }

    private static 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) throws Exception {
            handshakeFuture = ctx.newPromise();
        }

        @Override
        public void channelActive(ChannelHandlerContext ctx) throws Exception {
            handshaker.handshake(ctx.channel());
        }

        @Override
        public void channelInactive(ChannelHandlerContext ctx) throws Exception {
            System.out.println("WebSocket Client disconnected!");
        }

        @Override
        protected void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
            if (!handshaker.isHandshakeComplete()) {
                handshaker.finishHandshake(ctx.channel(), (FullHttpResponse) msg);
                System.out.println("WebSocket Client connected!");
                handshakeFuture.setSuccess();
                return;
            }

            if (msg instanceof FullHttpResponse) {
                FullHttpResponse response = (FullHttpResponse) msg;
                throw new IllegalStateException("Unexpected FullHttpResponse (getStatus=" + response.status() +
                        ", content=" + response.content().toString(CharsetUtil.UTF_8) + ')');
            }

            TextWebSocketFrame frame = (TextWebSocketFrame) msg;
            System.out.println("Received message: " + frame.text());
        }
    }
}

这个示例代码启动了一个 WebSocket 服务器，监听本地的 8080 端口。当有新的 WebSocket 连接建立时，服务器会将连接加入到一个列表中，当有消息发送到服务器时，服务器会将消息转发给所有连接。同时，客户端与服务器建立连接，发送消息并接收服务器返回的消息。