[comp.sys.mac.programmer] DDPWrite

mikeoro@hubcap.clemson.edu (Michael K O'Rourke) (07/01/89)

Does anyone know what would cause a DDPWrite to fail, giving an errcode of
-95 which corresponds to excessCollns?  I don't understand what the errcode
really means.  It seems like it is saying i have to many writes queued up,
but that is not possible because i only have one write queued up.

Also, has anyone experienced problems with NBP/ATP code working fine on
68000 machines, but failing when run on a 68020 or 68030 machine.  I have an
appletalk communications package i am developing and just run it on MacII and
SE30, only to find it crashes those machines.  Is there some trick to 
AppleTalk on those machines?


Thanx,
Michael O'Rourke

paul@taniwha.UUCP (Paul Campbell) (07/02/89)

In article <5889@hubcap.clemson.edu> mikeoro@hubcap.clemson.edu (Michael K O'Rourke) writes:
>Does anyone know what would cause a DDPWrite to fail, giving an errcode of
>-95 which corresponds to excessCollns?  I don't understand what the errcode
>really means.  It seems like it is saying i have to many writes queued up,
>but that is not possible because i only have one write queued up.

This actually ought to happen every so often (well not that often - it
depends on how busy your net is) - it's telling you that it tried to send the 
packet a number of times and each time it got a collision with another
packet on the net from another machine. This sort of thing is statistical
DDP is not reliable and you're supposed to lose some packets (the 
protocol you are running on top of DDP handles this, right? :-).

In practice if you get this back a lot it probably means a net with problems,
either it's noisy (wrapped around a fluorescent light or AM radio station
or something), or badly terminated (a phonenet like system without the 
terminating resistors in the correct place, or a LocalTalk system with a
long run with no box at the end), or there is another system on the net
which is doing something wierd.

	Paul
-- 
Paul Campbell    UUCP: ..!mtxinu!taniwha!paul     AppleLink: D3213
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