File transfer send callback prototype.
This function is called by the core when an outgoing file transfer is started. This function is called until size is set to 0.
public delegate void OnFileTransferSendDelegate(ChatMessage message, Content content, long offset, long size);
LinphoneChatMessage message from which the body is received.
LinphoneContent outgoing content
the offset in the file from where to get the data to be sent
the number of bytes expected by the framework
Warning : The returned value isn't used, hence the deprecation!