type Poller interface {
	// Add adds an existed connection to poller.
	Add(conn net.Conn) error
	// Remove removes a connection from poller. Notice it doesn't call the conn.Close method.
	Remove(conn net.Conn) error
	// Wait waits for at most count events and returns the connections.
	Wait(count int) ([]net.Conn, error)
	// Close closes the poller. If closeConns is true, it will close all the connections.
	Close(closeConns bool) error
}