Hi,
You don't have to deal with IoBuffer. It is used internally by AppWarp S2. The correct declaration of SendUpdatePeersNotification is as follows :
public void SendUpdatePeersNotification(byte[] update, boolean isUDP);
You can create a byte array and send it to a user via this method. isUDP represents whether you want to send that message using UDP or Not.
SendChatNotification can be used to send string messages where as SendUpdatePeersNotification is meant for sending binary messages. SendUpdatePeersNotification can be used to send messages over UDP or TCP. SendChatNotification only supports TCP.
Thanks