How to fix "io.netty channel.AbstractChannel$AnnotatedConnectException Connection timed out: no further information" [duplicate]

io.netty channel.AbstractChannel$AnnotatedConnectException Connection timed out: no further information

happens when you attempt to connect to a computer that you can connect to, does not have a server running.

This is because when Minecraft joins a server, it first pings for a server; remote computer on the other end, it first checks if said computer exists. This is handled by generic network code, and is on the operating system level. It succeeds because, well... A computer exists, and that the protocols running this isn't specific to Minecraft.
Then, it starts handshaking (tells the other computer "I'm a player; logging in to Minecraft now!"). Problem is that because there is no application listening to that port to handle the handshakes, the game then simply calls it a timeout, because it received no feedback as the computer on the other end, while existing, does not know what to do with the requests; so it just ignores them.

The AbstractionChannel$AnnotatedConnectException exception is a generic extendable exception class.

tl;dr

• The computer is online, but the server software is off.
  Start it up, basically.