Network HLAPI - How do I block the entrance of new clients to a server?

I have a game where I want to connnect with a host (server + client) and then block the connection for other users until the host is ready

I'm using the new Network Manager of Unity 5.1

I tried to limit the connections and then turning it back later, but it doesn't work, since 1 connection, I believe, makes it possible for 2 players to be online (1 player and 1 other connected to him/her) and 0 is not permited. Also, I didn't find any other means to make the server "not ready" and online at the same time, I just found it for clients, and I don't want to make the second client to enter the first room s/he finds just to wait for the host to be ready.

The purpose is: the first player must enter the scene first, set traps, position himself, and then open connection for another enemy player. Any clues? :)