class in UnityEngine.NetworkingSwitch to Manual
This is a network client class used by the networking system. It contains a NetworkConnection that is used to connect to a network server.
The NetworkClient handle connection state, messages handlers, and connection configuration. There can be many NetworkClient instances in a process at a time, but only one that is connected to a game server (NetworkServer) that uses spawned objects.
NetworkClient has an internal update function where it handles events from the transport layer. This includes asynchronous connect events, disconnect events and incoming data from a server.
The NetworkManager has a NetworkClient instance that it uses for games that it starts, but the NetworkClient may be used by itself.