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From: gandrews@netcom.COM (Greg Andrews)
Newsgroups: comp.unix.questions,comp.dcom.modems,comp.mail.uucp
Subject: Re: Data range used by UUCICO?
Summary: All 8 bits for the 'g' protocol.
Keywords: uucico
Message-ID: <1991Mar24.194612.4047@netcom.COM>
Date: 24 Mar 91 19:46:12 GMT
References: <1991Mar22.102630.1057@abekrd.co.uk>
Organization: Netcom - Online Communication Services  UNIX System {408 241-9760 guest}
Lines: 41

In article <1991Mar22.102630.1057@abekrd.co.uk> garyb@abekrd.co.uk (Gary Bartlett) writes:
>Can anyone tell me the range of data values sent by two communicating UUCICO
>processes.  Is it a full 8-bit range (0-255), a full 7-bit range (0-127) or
>a selected range of characters (eg 32-126)?
>
>I am most interested in finding out whether it uses the ASCII values for DC1/3.
>

The 'g' protocol would pass an XOFF (DC3) as part of the packet header 
whenever it sends a negative acknowlegement (NAK) for packet number 3 
(in the rotation of packet numbers from 0 to 7).  It would send an XON 
(DC1) when sending a NAK for packet number 1.

Almost as important, it would send an XOFF with the 8th bit set when
sending a data packet numbered 2, and the last data packet the sender
had received was numbered 3.  It would send an XON as part of the
header when sending a data packet numbered 2 when the last packet it
had received was number 1.

Every data packet is signalled by a control byte in the header that
has its 8th bit set.  Therefore, bytes above decimal 127 will appear
in the data stream.

Uucp 'g' does not 'escape' any characters that appear in the file
data.  If the file contains bytes corresponding to XON or XOFF,
they will be passed as-is through the modems.  If the file has been
compressed, it's almost guaranteed to have bytes above decmal 127
and below decimal 32.

In short, for the 'g' protocol, you need an 8-bit wide data path, and 
nothing between the sending computer and receiving computer must try 
to interpret any data bytes.  If you're using high-speed modems, they 
must NOT be set to use XON/XOFF flow control.  Any other devices in the 
data path must be completely transparent to data.


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|  Greg Andrews   |       UUCP: {apple,amdahl,claris}!netcom!gandrews    |
|                 |   Internet: gandrews@netcom.COM                      |
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