netty实现websocket

Netty是一个高性能、异步事件驱动的网络应用程序框架，用于快速开发可维护的高性能协议服务器和客户端，使用Netty实现WebSocket通信是一个相对简单的过程。

以下是一个简单的示例，演示如何使用Netty实现WebSocket服务器：

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
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.*;
import io.netty.handler.codec.http.websocketx.*;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;

public class WebSocketServer {
    private final int port;

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

    public void run() throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .handler(new LoggingHandler(LogLevel.INFO))
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast(new HttpServerCodec());
                            ch.pipeline().addLast(new HttpObjectAggregator(8192));
                            ch.pipeline().addLast(new WebSocketServerProtocolHandler("/websocket"));
                            ch.pipeline().addLast(new SimpleChannelInboundHandler<WebSocketFrame>() {
                                @Override
                                protected void channelRead0(ChannelHandlerContext ctx, WebSocketFrame frame) throws Exception {
                                    if (frame instanceof TextWebSocketFrame) {
                                        TextWebSocketFrame textFrame = (TextWebSocketFrame) frame;
                                        System.out.println("Received message: " + textFrame.text());
                                    } else if (frame instanceof PingWebSocketFrame) {
                                        ctx.channel().writeAndFlush(new PongWebSocketFrame(frame.content().retain()));
                                    } else if (frame instanceof PongWebSocketFrame) {
                                        // handle pong message
                                    } else if (frame instanceof CloseWebSocketFrame) {
                                        ctx.channel().close();
                                    } else {
                                        throw new UnsupportedOperationException("Unsupported frame type: " + frame);
                                    }
                                }
                            });
                        }
                    });
            ChannelFuture f = b.bind(port).sync(); // (7)
            f.channel().closeFuture().sync(); // (8)
        } finally {
            bossGroup.shutdownGracefully(); // (9)
            workerGroup.shutdownGracefully(); // (10)
        }
    }
}

这个示例创建了一个简单的WebSocket服务器，监听在指定的端口上，当收到WebSocket帧时，它会打印出收到的消息，它还处理Ping和Pong帧以及关闭帧。