reproduce.sh

#!/bin/bash

set -x

mkdir netty-bug
cd netty-bug

wget https://repo1.maven.org/maven2/io/netty/netty-all/4.1.51.Final/netty-all-4.1.51.Final.jar -O netty-all.jar

cat > Example.java <<EOF
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.epoll.*;
import io.netty.channel.nio.*;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.*;
import java.net.InetSocketAddress;

public class Example {
  public static void main(String[] args) throws Exception {
    EventLoopGroup bossGroup;
    EventLoopGroup workerGroup;
    Class clazz;
    if (args.length < 1) {
      System.out.println("Use epoll");
      bossGroup = new EpollEventLoopGroup(1);
      workerGroup = new EpollEventLoopGroup();
      clazz = EpollServerSocketChannel.class;
    } else {
      System.out.println("Use nio");
      bossGroup = new NioEventLoopGroup(1);
      workerGroup = new NioEventLoopGroup();
      clazz = NioServerSocketChannel.class;
    }

    ServerBootstrap b = new ServerBootstrap();
    b.group(bossGroup, workerGroup)
        .channel(clazz)
        .childHandler(
            new ChannelInitializer<SocketChannel>() {
              @Override
              public void initChannel(SocketChannel ch) throws Exception {}
            });

    ChannelFuture f = b.bind(new InetSocketAddress("[::1]", 0)).sync();
    f.channel().closeFuture().sync();
  }
}
EOF

javac -cp netty-all.jar Example.java

# Use NIO
java -cp netty-all.jar:. Example nio

# Use Epoll
java -cp netty-all.jar:. Example