Going to https://localhost:9001 yields some nastiness:
==> es.log <==
2020.06.05 13:15:48 WARN es[][o.e.t.TcpTransport] exception caught on transport layer [Netty4TcpChannel{localAddress=/127.0.0.1:9001, remoteAddress=/127.0.0.1:38526}], closing connection
io.netty.handler.codec.DecoderException: java.io.StreamCorruptedException: invalid internal transport message format, got (16,3,1,2)
at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:472) ~[netty-codec-4.1.32.Final.jar:4.1.32.Final]
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:278) ~[netty-codec-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.handler.logging.LoggingHandler.channelRead(LoggingHandler.java:241) [netty-handler-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1434) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:965) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:656) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKeysPlain(NioEventLoop.java:556) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:510) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:470) [netty-transport-4.1.32.Final.jar:4.1.32.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:909) [netty-common-4.1.32.Final.jar:4.1.32.Final]
at java.lang.Thread.run(Thread.java:834) [?:?]
Caused by: java.io.StreamCorruptedException: invalid internal transport message format, got (16,3,1,2)
at org.elasticsearch.transport.TcpTransport.readHeaderBuffer(TcpTransport.java:851) ~[elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.transport.TcpTransport.readMessageLength(TcpTransport.java:837) ~[elasticsearch-6.8.4.jar:6.8.4]
at org.elasticsearch.transport.netty4.Netty4SizeHeaderFrameDecoder.decode(Netty4SizeHeaderFrameDecoder.java:40) ~[transport-netty4-client-6.8.4.jar:6.8.4]
at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:502) ~[netty-codec-4.1.32.Final.jar:4.1.32.Final]
at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:441) ~[netty-codec-4.1.32.Final.jar:4.1.32.Final]
... 19 more