My friends can not enter the server

Hello, i´m have a Server with SpongeForge, if i enter everything is Ok, but if my friends try to enter they start to fall to the void and disconected for timeout, and in the console have this error:

[Netty Server IO #4/ERROR] [FML]: NetworkDispatcher exception io.netty.handler.timeout.ReadTimeoutException: null

Could someone please help me?

PD: Sorry for the bad english, i speak spanish and only know some english.

Does this happen without SpongeForge installed? It looks like severe lag - is that the only error that shows in the console?
We really need more information to debug. Important things like what version of Java, SpongeForge, Forge and plugins you are using can sometimes help isolate the problem.

We haven´t tried without spogeforge, but the Java version is 8 upgrade 201, forge version is 1.12.2- and SpongeForge is 1.12.2-2768-7.1.5, we tried without spongeforge when we can, Thanks for the help.

Without spongeforge is the same thing, and it is the only error.