Allows the client to create a server only session which means that once created, you will not appear on the connected clients list. Transferring instance ownership or taking control of it will not be possible as once you are disconnected from the server everyone will be kicked from the session.
{"msg":"server_only","SessionID":"my_session_id_here","Title":"my_application_title","max_clients":40,"whitelist":0,"passkey":"Leave blank for none","default_values":0}

The server will create a server only session and respond with:
{"MSG":"created_session","SessionGUID":"my_session_id_here","Sockets":[],"SocketID":0,"InstanceOwner":0,"Title":"my_application_title","MaxClients":40}