Minecraft Error internal exception io.netty.handler.codec.decoderexception java.lang.nullpointerexception?

As of today I have the problem internal exception io.netty.handler.codec.decoderexception java.lang.nullpointerexception when I want to join my server
But I can find other servers

The server may be down. Zero pointer exception normally means that you are pointing to something undefined (i.e. Pointing to nothing). I would conclude from this, but am not sure that the server is no longer available.

The server was restarted

For something to be zero, the server must first be running - if it were not on, the error message would also be different. Of course, the server can also get a NullPointerException from the client, but it is not.

Is there an error message in the console? If so, it would be useful.

Internal exception io.netty.handler.codec.decoderexception java.lang.nullpointerexception

What can I do but I also use an app that connects to the acc and it doesn't work either, it is just my servers that all others go

If it's your server, shut it down and up again, or you can still load an older version of the server, provided you have always saved

Others just don't come to the server

The whole error message?

That is what comes when joining n

If it's your server, you should have access to the console, what's in there?

sssds