JJW@SAIL.STANFORD.EDU (Joe Weening) (08/21/86)
I'd like to find out what reasons people have for using Telnet binary
mode. Do you use it for any of the following?
a. To allow setting the 8th bit along with an ASCII character;
b. To avoid the NVT CR/LF conventions;
c. Some other pre-arranged interpretation between the hosts. If so,
how is this interpretation agreed on?
I've recently discovered that reason (a) is often unnecessary because many
systems allow the 8th bit without complaint. (Is this a bug or a
feature?) It seems easier to not use binary mode, and put up with the NVT
CR/LF conventions, to avoid a disagreement between the two sides about the
meaning of binary mode.MRC%PANDA@SUMEX-AIM.ARPA (Mark Crispin) (08/24/86)
Joe -
A purist would argue that NVT ASCII is 7 bits unless binary mode has
been negotiated. The Telnet specification is vague on this point, but it
does refer to the "128 possible characters in NVT ASCII" in a few places.
I believe that 8 bit transmission in non-binary mode is a bug, since it
interferes with local parity handling.
The parity issue is important, although many implementors (myself
included, alas) have never bothered to implement parity correctly.
I know that vanilla DEC TOPS-20 does not enforce 7-bit NVT ASCII on
input to an NVT. It also doesn't enforce IAC doublings on output from an
NVT. I consider both of these to be bugs, in spite of the fact that
certain individuals have written programs to exploit them. The PANDA
versions of TOPS-20 (SIMTEL20, STL-HOST1, DREA-XX) all have these bugs
fixed, as do several other sites.
Significantly, the TAC also enforces 7-bit ASCII in non-binary mode.
I think that it is prudent to negotiate binary mode on any Telnet
connection in which you wish to transmit 8-bit ASCII. The only hosts I
know of which have problems with binary mode are certain broken versions
of Unix. As far as I can tell mainstream Unix handles binary mode
reasonably.
-- Mark --
-------MRC%PANDA@SUMEX-AIM.ARPA (Mark Crispin) (08/24/86)
Vint -
I don't know the answer to your question. Most hosts don't offer
a way out, but PANDA TOPS-20 systems have a TERMINAL NETWORK-BINARY command
with an optional argument of BOTH, INPUT, or OUTPUT (the default is BOTH)
to get into network binary from the host (in addition to client means such
as TAC @ B I S and @ B O S) and a corresponding TERMINAL NO NETWORK-BINARY
to get out.
I think that all hosts should have such a facility if 8 bit I/O is at
all meaningful on NVT's.
-- Mark --
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