[ale] Q: IEEE-Float byte order on Network convention

[Richard Whitfield]

If I remember correctly from many years ago there was something called xdr
(eXternal Data Representation) that was part of RPC. It was a pair of
functions to convert data structures to a standard format for transmission
to another computer, and another function to read the standard format and
convert to the native format of the local processor. The functions were
available for various cpu types/operating system environments. I prefer this
concept than the current fetish for encoding everything into ASCII text for
external transmission.

Regards,

Richard Whitfield
Megatrend Information Services Ltd.
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rcw at megatrend.com.hk


-----Original Message-----
From: John Mills [mailto:jmills at tga.com]
To: ale at ale.org
Sent: Wednesday, 2 August, 2000 10:46 PM
To: Atlanta Linux Enthusiasts
Subject: [ale] Q: IEEE-Float byte order on Network convention



Hello -

A question for network gurus:
 I plan to send binary packets including IEEE floating-point types over an
InterNet connection between a client and server. The client will initially
be hosted on an i86 box (interchangeably Linux or WinNT), and later
possibly a PPC box. The server could be a variety of Win or *nix hosts. I
will write the code for client and server, but not the net interfaces.
Transport will be TCP/IP and UDP/IP, will probably use SSL, and may use
HTTP tunnelling. (I am new to detail on most of these: please excuse any
obvious contradictions, but do bring them to my attention.)

I have only done this with packets of my own design on a direct serial
links between 68K and i86 boxen: the natural orderings were indeed
different, but (thankfully!) the data types were otherwise compatible for
the respective compilers. (I put reordering responsibiliy on the
i86-hosted responders, since they had the lowest overall loading in that 
net.)

If there is a convention for byte- and word-order in transfering
non-integer types over a net connection, I would prefer to observe it.
Please tell me of any, direct me to references, or share your
experiences.

TIA for any comments.

 - Mills

   John Mills
   Sr. Software Engineer
   TGA Technologies, Inc.
   100 Pinnacle Way, Suite 140
   Norcross, GA 30071-3633
   e-mail: jmills at tga.com
   Phone: 770-441-2100 ext.124 (voice)
          770-449-7740 (FAX)

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