I am currently working on a test application involving a server and several client. The communication is achieved through the use of the TCP/IP protocol.
The server has several slots available. When a client connects, this one is affected to a slot. Is there a reliable way to identify if a disconnected client has reconnected? 
I would like to reassign the disconnected client to its previous slot.
I do not really ask for code, but just clues that could help me to solve this problem.
Thanks for your answers. 
Edit
Working with MAC addresses should do it, login/pass, or pass-phrases.
Working with MAC addresses should do it, login/pass, or pass-phrases. – Papipone
Python3 knwowing if a disconnected client has reconnected