Hey, what packet I have to use to know host name ?
Is there any way to know that players joined on server (player's username)

Sorry for my bad english

Hi.
To get the host name of the current server, I use IS_ISM packets and simply just do ISM.HName. Good enough for me.

Then in InSimMulti void:

Although, I don't understand your other question.
Hopefully I'm of some help to you.