Date   : Mon, 11 May 2009 20:40:37 +0100
From   : robert@... (Rob)
Subject: net monitor - help pls!

On 11/05/2009, Chris Johns <chris@...> wrote:
>> Just need to work out why the **** beeb is trying to resend the scout,
>> when I acked it, and how I'm suposed to spot that..
>
> Does AUN use 4-way handshake in the same way as Econet? I thought it
> just sent the data in a UDP packet, and didn't bother with the scout.

Nope ... just a two way handshake - the AUN UDP packet has a sequence
number in it, and there's an ACK packet containing the same sequence
number sent back on receipt, so the transmitter knows it's been
received.

I'm faking the first ack to the beeb in response to the scout, and
buffering the scout and it's control byytes so I can add the data
packet to it and send the lot as a UDP packet when that arrives.  I
then issue the final ack back to the beeb when I get the ack from the
remote AUN host.

(I'm probably leaving myself open to lots of bugs should there be more
than one host tring to talk to the emulator at the same time, but I'll
worry about that later!  The Beeb being emulated wouldn't be able to
deal with that anyway.)

What I've been seeing so far is
scout->
<-ack (faked)
scout-> which i think is data, so send to the remote host,
     (get ack from aun host)
<-ack
data->  (which fails to be interpreted as a scout ...)

I'd assume that my first ack is at fault, so the beeb is resending,
but not quite sure how it could be - it's only four bytes after all!!
It might be a timing issue, but I'm using the same timing as the
current pseudo-econet code, which does work..

Not had chance to play with it today, but will have another go later
when the kids are settled..

rob