Hi,
This version probably not being supported any more but i like to give it a shot in hope it can be fixed.
While playing allot of different mod packs they come in 1.12.2 of forge.
I noticed since 1.12.2 once the server has been started i can play normally but after a while if i disconnect and want to connect again i cannot see the server anymore.
And i have to restart the forge server.(with pretty mutch all builds )
I had the same issue with spigot and received the same error and in spigot mc they have fixed this.
See this link: https://hub.spigotmc.org/jira/browse/SPIGOT-3418
The ref netty link in the spigot issue mentioned: https://github.com/netty/netty/issues/6607
See also below the error i have in forge 1.12.2 it looks the same.
I hope this still can be fixed so i dont need to constant reboot the forge server so i can play.
Im using windows 2012 R2 to run the server though just in case this matters with the bug fix that needs to take place.
> Mar 26, 2020 1:54:50 AM io.netty.channel.nio.NioEventLoop select
WARNING: Selector.select() returned prematurely 512 times in a row; rebuilding Selector io.netty.channel.nio.SelectedSelectionKeySetSelector@627ff08a.
Mar 26, 2020 1:54:50 AM io.netty.channel.nio.NioEventLoop rebuildSelector0
WARNING: Failed to re-register a Channel to the new Selector.
java.lang.ClassCastException: io.netty.channel.nio.SelectedSelectionKeySetSelector cannot be cast to java.nio.channels.spi.AbstractSelector
at java.nio.channels.spi.AbstractSelectableChannel.register(Unknown Source)
at io.netty.channel.nio.NioEventLoop.rebuildSelector0(NioEventLoop.java:347)
at io.netty.channel.nio.NioEventLoop.rebuildSelector(NioEventLoop.java:318)
at io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:769)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:388)
at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:858)
at java.lang.Thread.run(Unknown Source)