Trying to make a Pictochat like program, but I'm stumped.

I am working on a system to transfer large amounts of data between two consoles, too. I have a simple protocol. The sender sends a signal with MPSET whenever it has new data it wants the receiver to see, and the receiver sends a signal with MPSET whenever it has finished receiving that piece and wants the sender to send more. They each see the others' signal using MPGET, which never causes a buffer overflow. Details, chronologically: For sender and receiver, I set MPSET 0,0 before MPSTART. The sender does MPSEND, then MPSET 0,1. The receiver is watching MPGET(sender,0) until it changes. Once the receiver sees this change, it knows it can MPRECV. Then, the receiver does MPSET 0,1. The sender, after sending the first string, is watching MPGET(receiver,0), and when this value changes, the sender knows it can send the next string without causing an overflow at the receiver. It does MPSEND, then MPSET 0,0. The receiver is waiting for MPGET(sender,0) to change back, and so on. Details, by system: Sender: MPSET 0,0, MPSTART, MPSEND, MPSET 0,(something different from the last value it had), wait for MPGET(receiver,0) to change, then MPSEND again, etc. Receiver: MPSET 0,0, MPSTART, wait for MPGET(sender,0) to change, MPRECV, MPSET 0,(something different from the last value it had), then wait on MPGET again, etc. In my implementation, I flip the MPSET value between 0 and 1 while there is still more data to transmit, and MPSET 0,2 for the very last piece of data. EDIT: In my tests, I can send four strings for each iteration of this protocol, and each iteration is typically 6 frames. I'm getting throughput of 9900bytes/second. EDIT 2:I just ran a test for 10 minutes; no errors, approx 6GB transferred. It seems quite stable.