Re: Ethernet Modems

[Jeff Blakeney <CUTjblakeney@sympatico.ca>]

On Sat, 4 Dec 2004 10:33:28 -0700, "Terry Olsen"
<tolsen64@hotmail.com> wrote:

>Do you know if this sofware will allow for file transfers?  All of the 
>programs I've tried for Windows only pass "characters" and therefore file 
>transfers (X/Y/Z modem) don't work.  I'm looking at the hardware box because 
>it will allow file transfers, also I won't need to depend on another pc to 
>make the connection for me.

Are you sure you're not just running into the problem that file
transfer protocols like X/Y/Z modem don't work particularly well over
TCP/IP connections?  I remember doing file transfers with Spectrum
over a dial-up TCP/IP connection to Delphi (back when they still had a
text interface) and the file transfers were very slow, had to have
quite a number of retries and would sometimes even fail.  I seem to
recall others having even less success than I did.

I believe it comes down to the timeouts that the X/Y/Z modem protocols
use and the fact that TCP/IP won't necessarily get the next packet to
your communications program within that time.  This can be partly
explained due to the fact that TCP/IP doesn't need to send things in a
consecutive manner.  A simplified example:  you could receive a TCP/IP
packet with block 2 of an Xmodem transfer before you receive the
TCP/IP packet with block 1 for instance but your communications
program won't receive anything until the TCP/IP packet with block 1
arrives.

It seems strange to me that programs or hardware would purposely limit
themselves to only working with 7 bit characters instead of 8 bit.

-- 
 Jeff Blakeney - Dean of the Apple II University in the
                 Apple II Community on Syndicomm.com
 CUT the obvious from my address if you want to e-mail me