使用java 和 netty 编写TCP客户端代码

好的，我可以回答这个问题。以下是一个简单的使用Java和Netty编写TCP客户端代码的示例：

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringEncoder;

public class TcpClient {
    private static final String HOST = "127.0.0.1";
    private static final int PORT = 8080;

    public static void main(String[] args) throws Exception {
        Bootstrap b = new Bootstrap();
        b.group(new NioEventLoopGroup())
            .channel(NioSocketChannel.class)
            .handler(new ChannelInitializer<SocketChannel>() {
                @Override
                public void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(new StringEncoder(), new TcpClientHandler());
                }
            });

        Channel ch = b.connect(HOST, PORT).sync().channel();

        ch.writeAndFlush("Hello World!\r\n");

        ch.closeFuture().sync();
    }

    private static class TcpClientHandler extends SimpleChannelInboundHandler<String> {
        @Override
        public void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
            System.out.println("Received message: " + msg);
        }

        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
            cause.printStackTrace();
            ctx.close();
        }
    }
}

该代码使用Netty的Bootstrap创建一个TCP客户端，并在连接后发送一条消息。接收到来自服务器的消息时，客户端会将其打印到控制台上。在客户端发生异常时，它将关闭连接并打印异常堆栈跟踪。