Cant join a minecraft sv

Hello, I've been playing with a friend a modded server I started yesterday with Hamachi, I can join the sv and he could before today but now he cant connect for some reason and I dont really know what. I have changed the timeout to 512 because his pc isnt so good but he suddenly disconnects while attempting to join, Here is what appears everytime he wnats to join:

[22:26:02] [Netty Server IO #7/ERROR] [FML]: NetworkDispatcher exception
java.io.IOException: Se ha forzado la interrupción de una conexión existente por el host remoto
        at sun.nio.ch.SocketDispatcher.writev0(Native Method) ~[?:1.8.0_251]
        at sun.nio.ch.SocketDispatcher.writev(Unknown Source) ~[?:1.8.0_251]
        at sun.nio.ch.IOUtil.write(Unknown Source) ~[?:1.8.0_251]
        at sun.nio.ch.SocketChannelImpl.write(Unknown Source) ~[?:1.8.0_251]
        at io.netty.channel.socket.nio.NioSocketChannel.doWrite(NioSocketChannel.java:432) ~[NioSocketChannel.class:?]
        at io.netty.channel.AbstractChannel$AbstractUnsafe.flush0(AbstractChannel.java:856) [AbstractChannel$AbstractUnsafe.class:?]
        at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.forceFlush(AbstractNioChannel.java:368) [AbstractNioChannel$AbstractNioUnsafe.class:?]
        at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:618) [NioEventLoop.class:?]
        at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:559) [NioEventLoop.class:?]
        at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:476) [NioEventLoop.class:?]
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:438) [NioEventLoop.class:?]
        at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:858) [SingleThreadEventExecutor$5.class:?]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_251]
[22:26:02] [Server thread/INFO] [minecraft/NetHandlerPlayServer]: carlituss lost connection: Disconnected
[22:26:02] [Server thread/INFO] [minecraft/DedicatedServer]: carlituss left the game