Client.java

package com.kwan.shuyu.onlytest;

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;
import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import lombok.extern.slf4j.Slf4j;

@Slf4j
public class Client {
    public static void main(String[] args) throws InterruptedException {
        final NioEventLoopGroup group = new NioEventLoopGroup();
        LoggingHandler LOGGING_HANDLER = new LoggingHandler(LogLevel.DEBUG);
        try {
            final Channel channel = new Bootstrap()
                    .group(group)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<NioSocketChannel>() {
                        @Override
                        protected void initChannel(NioSocketChannel ch) throws Exception {
                            ch.pipeline().addLast(LOGGING_HANDLER);
                            ch.pipeline().addLast(new StringEncoder());
                            ch.pipeline().addLast(new StringDecoder());
                        }
                    })
                    .connect("localhost", 7777).sync().channel();
            final ByteBuf buf = ByteBufAllocator.DEFAULT.buffer();
            buf.writeBytes("abcdfmw9".getBytes());
            channel.writeAndFlush(
                    buf
            ).addListener(promise -> {
                if (!promise.isSuccess()) {
                    Throwable cause = promise.cause();
                    log.error("error : ", cause);
                }
            });
            channel.closeFuture().sync();
        } catch (InterruptedException e) {
            log.error("client error", e);
        } finally {
            group.shutdownGracefully();
        }
    }
}