Really thanks for your information's.- You were right about closing connections
I probably didn't wait enough and when checking connections and port numbers they were still open.
In previously message I meant different ip's from clients, not that they are connecting to different server ip - Sorry to misslead you.
I resolved the problems for sending a command to selected client, without waiting him to respond.
I've adopted a chat script that suggested beneath - Works perfectly!

Thanks again to both of you for helping me!

Regards, Igor V.