Where does TcpFull know no more data needs to be sent?

[Eclipse612]

Hello,

I'd like to have the FullTcp agent call a certain method at the appropriate time, but can't find the spot to put the call in.
The agent is sending a - let's call it that way - "application data object". Of course, it sends little 536-byte segments until the total bytes sent reach the size of the given "application layer payload". I want the sending agent to make the call when all bytes have been sent and all acks have been received, so that I can tell the application layer to send another data object. Where do I put the call?

Thanks in advance!