stever@videovax.Tek.COM (Steven E. Rice, P.E.) (01/14/88)
I am looking for information on character mappings that are used or have
been used to allow the transfer of binary (8-bit) data through channels
that cannot pass all byte values. There are, of course, the various Hex
schemes, which simply encode each byte as two ASCII characters, but the
efficiency seems to be poorer than is necessary. Is there a standard
8-bit to 6-bit mapping (in which 3 bytes are encoded as 4 characters for
transmission) that avoids these problems?
The mapping used in UUENCODE and UUDECODE has problems with some BITNET
sites, which change some of the special characters. Frank daCruz wrote
in his book on Kermit that if they had it to do all over again, they
wouldn't be quite so ambitious with their use of the character set
(characters from space through tilde are used, as well as various
control characters).
I would like to be able to map arbitrary data streams to a "safe"
set of characters for transmission through a potentially-hostile
serial path. I was thinking of using the upper- and lower-case
letters (52), the digits 0 through 9 (10), and the "+" and "-"
signs (2), for a total of 64 characters. Is this safe, or will I
find some network node converting all my lower-case letters to
upper case?
I'm certain there are many of you who have faced just such a problem.
If you can shed any light on the issue, please send email to me at the
address below. Thanks!
Steve Rice
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