How to determine to which server instance the client is connected to send a message?

Question

.NET

Almost everything is in the title. There is a service where several instances of the tcp server are deployed. Clients connect to them through a load balancer. How to find out which instance of the server a particular client is hooked to in order to send a message to it (to the client) through this server?
There is an idea to save the server identifier at the time of connection in, for example, Redis.
Desirable solutions within Microsoft and azure technologies.