title: How to enable gRPC server to support just one client connection
body: <p>I'm currently considering to use gRPC for basically inter-process communication between Java app (client) and C++ server. The RPC calls will use functionality from very old C++ code base which is definitely not thread-safe. 
  Normally the Java client will start more gRPC server instances and have just one connection with each server instance.
  Is there any way how to ensure this on the gRPC server to accept just one connection and refuse all other attempts for connection.  Otherwise I need to introduce some global lock in the RPC functions to have 100% correct server implementation.</p>