[Twisted-Python] Knowing end of packet

Hello, I am sending a large amount of data to a twisted server. I want to know how the protocol class knows that no more data is to be received. I dont pass the length of the data in the packet, hence I'm looking for a termination field in the packet.Like </MESSAGE>. I did see a logging class but not sure if thats what I want. If I have to overload the dataReceived method, and buffer the data until I see the termination field thats ok, just need to know if this seems correct in twisted. Much appreciated for any help. Thanks, Garyc